Please, Dr. Hossenfelder, do a video on what "observation" and "looks at" and "measure" mean in quantum mechanics. Obviously the universe didn't start acting differently when physicists were invented and started measuring things - non human quantum interactions must also have these same effects. What are they?
No disrespect to Dr Hossenfelder, but I personally wouldn’t seek her input regarding these issues (at least not authoritatively) In fact I suspect she wouldn’t like hearing this notion, but this is an area of physics where the field of Philosophy can be credited with “de-obfuscating” the illegible mess that theorists left Quantum Mechanics. I mean, to the extent that physicists had actually addressed a lot of conceptual baggage that it was wallowing in, a simple question such as yours regarding these ridiculous descriptions of nature and what you were supposed to call whatever scientists were doing to nature (looking at it? measuring it? observing it?) would result in no consistency and very little progress on the conceptual domain. Even worse was the fact many physicists who were interested in conceptual questions, or what is commonly recognized today as “the foundations of Quantum Mechanics” were straight up fired and blacklisted! I highly recommend some of David Alberts talks or interviews where he discusses the way many careers were destroyed-like LITERALLY destroyed-for questioning the dogma of the standard Copenhagen interpretation of Quantum Mechanics
@@mrosskneOnce again, this is a somewhat more philosophical question, or at least a more foundational question that depends on an understanding of how knowledge and certainty interact in the scientific model. You asked “how can we be certain …” and the scientific answer to that is always going to be “we can’t.” But for scientists, this is never a concern, because scientists aren’t interested in certainty, they are interested in probability. So let’s ask this a different way: How can scientists make assumptions about how the universe acted in the past, given those assumptions are found to have an associated probability measure?
I find it puzzling how these effects involve a single particle, while being "observed", "watched" or "measured" requires interactions of gazzilion other particles. My lizzard brain can't get around this.
@@karelsmutny7038 I watched a video a while ago (I forget the name of the presenter) which explained that Shrodinger's wave equations were not wave equations in the true sense of the term but more closely resemble heat equations, which makes some sort of sense to me - thermodynamics being about the statistical properties of lots of little things interacting involving heat and entropy, and quantum mechanics being random or statistical, to some extent. So, perhaps observation of quantum events is like watching a kettle boil? They really do boil when watched (I've often repeated the experiment), but it does seem to take longer.
At age 12 (a long time ago, now), I disproved "a watched pot never boils". I'm not sure why I haven't received notice from the Nobel folks just yet, but I reckon the physics prize is wide open now.
@@aarionsievo There is a very distinctive difference between a radioactive nuclei and the typical 2 level (but could be more states) System you use for the Quantum Zeno effect. You build a 2 level system that would rotate between the 2 states that starts in state 1. Then you continuously try to measure if it is in state 2 (you could also measure if in state 1, but that is less impressive and maybe more disruptive) and that keeps in in state 1, because a small rotation still give nearly 100% probability for the original state. The decay of the nuclei is not such a nice 2 level system. The decayed state is a multitude of states and usually better described like a macro state. In the principle description the non decayed state rotates into other states that than again rotate in further states and so on and so on (that is how decoherence happens in principle. Theoretically it could rotate back, but that only really happens for systems with very few states). And you would have to measure all the states that interact in first order with the non decayed state. And that is not possible.
funnily now that i have optical fiber, rarely i get a frozen download, i kinda watch all to see if some gives problems, but mostly to see hundreds of gigabytes downalod to my storage in minutes, not in weeks
The pot alone is not the problem, you need milk, too! Watched milk will not boil but look in the other direction for a second and your in for a long cleaning session on your induction stove!
If you're checking state 2, you're doing something to it, and preventing that particle from going there. Measuring state 2 involves using a device that has some kind of current, which generates an electromagnetic field, which alters the local charge field in the experiment. but its not just a mathmatic field of numbers or some immaterial ether -- its a field of real photons with spin which effect the path of the particle not with magic or memory or time travel - but through physical bombardment.
I mean, if we assume collapse does happen for whatever reason and however it does (which I see no reason we shouldn't assume), I'd expect this to also work for the same reasons and roughly the same way. What I find interesting here is what this example might be able to say about such reasons and workings. Like, could one calculate the effect and interactions as you describe to explain it, and would that work independently of how exactly the measurement is made? If not, does this point to some more "fundamental" properties for the collapse? Anyway, sorry if I'm mostly rambling : p
But how does state 2 interact with state 1? I guess we could do this experiment with entangled particles over a distance that doesn't allow physical interaction within the given timeframe.
No, you're not preventing the particle from moving to state 2. The Zeno effect was predicted and calculated before it was experimentally tested, and has been proven using multiple measurement techniques and methodologies.
The "memory" you're talking about is basically the particle being reset by the measuring interaction. I'm pretty sure you could do that with radioactivity, too, but then you'd need a measuring device that can actually interact with the particle without destroying it, and at those energies and such a small scale that's just not an option.
But the states aren't "places". If you're watching a particle to see if it's in state 2, but the particle is in state 1, you're still interacting with that particle.
I caught that too. Unless I'm missing something, then watching for state 2 of the particle *should* have the same effect as watching for state 1 because you're still observing the same particle, and I really hate the term observing because it introduces spooky psuedoscience like the particle is conscious and somehow aware of our attention which is not the case at all.
This is my opinion, as well. The act of measurement at either state 1 or 2 can have the sane overall effect on the particle. The unfortunate aspect of QM is the sloppy and irregular language used. It tends to create false impressions and weird claims that don’t hold up well to a careful dissections of the facts.
@@damianGray I'm not a quantum physicist but what you are saying makes sense to me. How can one observe anything without changing the state from what it might have been if you had not observed it. Observation is a physical act. What is interesting about this is that we will never know what role consciousness plays in the Zeno effect. There are so many other things involved in the act of observing besides consciousness that no experiment could ever eliminate.
1:40 - "just check that the particle is not in state two" - well that is still interacting with the particle, so yeah, there's no such thing as measurement independence when working with quantum effects. I don't understand what's different here than just saying that an observation is an interaction, and an interaction effects the state of the system.
The elephant in the room is that the whole of science is based - whether it is aware of it or not - on the basis of the godlike 'detached observer' who measures, but never affects. That's why quantum physics rapidly becomes unintelligible to people talking in terms of classical notions like 'observable universe' etc etc.
@@Ajay-kz9ns When you look at a thing in the macro world, photons hit it and it sends photons back to your eyeball, but the photons usually don't have much effect on the thing you are looking at. In the quantum world when you "look" at a particle, just one photon (or any other particle) can change the state of the particle being observed, so the only way to observe a particle is to interact with it.
@@doubletribble-yt when you look at something you aren't shooting photons out of your eyes though, you are just receiving photons that were heading towards you anyway right? Or is this more a consequence of needing to specifically shoot a photon or particle at another in order to get your screen blip telling you which state it is in because you can't actually see a quantum particle with the naked eye?
my question is: are we sure that when we observe if the 2nd state wasn't reached, we aren't also interacting with the 1st state? Like for example, checking the 2nd state 'fills it in' which makes it impossible for the quantum whatnot in the 1st state to move.
If you're checking state 2, then you are necessarily checking state 1 (given the situation where the thing you are looking for must be in one of those two states.)
The experiment should be devised so that the test subject is free to move into any state with an equal probability. It doesn't really matter that you are choosing the 2nd state over the first. The measurement "locks in" that value for that "round" of the experiment. That is why it gives these "spooky" results. Its a red herring anyway because what the "zeno effect" is really measuring is the probability over a given time, not that the probability goes up over time. To see the true probability distribution think of a pinball machine that has multiple targets, once it bounces off the first it resets and can hit another, but the score accumulates.
@mrmouse4121 No one talks about the underlying metric of reality supporting both the existence of the.'particle' and the 'states', in terms of degrees of freedom...
@@obsidianjane4413 I fear that I don't understand enough physics to be able to interact with quantum in a manner that isn't metaphors and analogies. Which quickly devolves into wrong assumptions which are a pain to unlearn- especially with a subject that is so far from what humans are used to observe.
Around 1:48 you're still interacting with the system even if you're only checking where the particle isn't. Claiming this is weird is akin to placing a detector at only one slit in a double-slit experiment, then acting surprised you have a clump pattern behind both slits.
@@mrosskne because the particle is a wave, and measuring where it could be and finding it's not there is interacting with the wave, which causes a collapse
Petition to make physicists stop using words like "observing" and "looking at" in context of explaining Quantum Mechanics to regular audiences. Just say "interacting", or "literally bombarding it with other particles" to make it all less spooky. You people are never simply looking at something anymore than a tree is looking at a car wrapped around it next to the highway.
Sorry it's strange regardless of words used. And it is certainly fine to say Observe, when that is what we are doing even if it's not with our eyes, just as people observe the world with multiple senses, so do the scientists observe via various methods.
She explicitly noted it's not about direct interaction, you can observe the "empty slot at state 2" and that will keep the particle at state 1 without interacting with it directly.
@@franesustic988no it's not. It like studying a rare nocturnal buttefly with a flamethrower and wondering why they're look...and smell, different than you expected
"watching" a radioactive decay is diffrent than "watching" an ultracold lattice gas (the paper mentioned) -- if by "watching" a radioactive decay we mean looking at a Geiger counter. The Geiger counter goes off *after* the decay has already happened, it doesn't interact with the radioactive atom. But "watching" the ultracold gas does involve interacting with it. If we had some way of measuring the state of the radioactive atom directly, then we could perhaps have a zeno effect (or anti-zeno effect .. speeding up the decay).
I also thnk it's not fair to talk about the memory-less-ness of radioactivity. That is true if you have many atoms that you are "looking at". But each individual atom can only decay once (so we can't speak of memory .. once it has decayed, that particular atom won't decay anymore). I think the fair comparison is between a single radioactive atom that can decay, and the thought experiment atom with levels 1 and 2. Then, they are in fact the same kind of system -- but the difference is the assumed measurements being done in each case, as mentiond in my original post.
As I understand it, memorylessness is a property of a probability distribution such as the exponential distribution, which radioactive decay obeys. If I understand correctly, a subatomic particle has NO physical way of storing the information ”for how long time have I still not decayed”, therefore it must obey exponential distribution and zeno effect will never work on it. The superposition states where zeno effect can work seem to require some other, special kind of a propability distribution that is able to ”gain progress” over time, evolving towards state 2 over time, and if it is observed at state 1, then its ”progress” and wave function is reset. Even if we would look at a subatomic particle directly to see if it’s decayed or not, that’s a different case, because in that specific probability distribution there is no ”progress” to reset - radioactivity distribution is simply some constant probability per infinitesimal time to decay.
@@maxsamarin9002original paper was about how zeno effect leads to deviation from exponential decay law. Basically, the law is an approximation if your observation period is much bigger that time evolution of state. Quantum states evolves very fast, so you see effect only if observe system extremely often.
There was serious criticism to experiments with cold atoms 10 years ago. Basically, probably they didn't show zeno effect. One part of criticism was exactly what you said. Maybe I'm BSing now, but according my impression, there is no established good experiment that undoubtedly demonstrated zeno effect.
This sounds perfectly in line with the measurement apparatus getting entangled with the experiment during the measurement. Before the measurement the particle is in a superposition of state 1 and 2. After measuring it once, the whole setup is now in the superposition of (1, we've measured 1) and (2, we've measured 2). Now if we only consider the first part of the superposition, after a while it will shift to a superposition of (1, we've measured 1) and (2, we've measured 1) and if we measure it once more, we will again get a superposition of (1, we've measured 1 and 1) and (2, we've measured 1 and 2). The "paradox" occurs because 1) as you said in the video, the probability density of the state changing starts at 0 and only increases after the measurement and 2) our measurement apparatus is not isolated from our bodies and so we're getting entangled with the "almost certainly 1" states as they are measured (or the wave function collapses, if that's how you prefer to think about it).
If you shortly observe the system for the state 2, you observed it and influenced it, resetting the "timer". It would only be the strange if you expect some particle ending up at some isolated position, and particle never gets there because you frequently check if the particle is there. As for the prison guard and prisoner analogy, it would be like if the prison guard is checking outside of the prison if the prisoner is trying to escape. And strangly, he never tries to escape because guard is looking outside, but the prisoner cannot know if the guard is looking outside. It would only be strange if quantum systems would behave like that.
The important difference with radioactive decay is that you're not actually observing - and interacting with - individual nuclear states. You're just catching radiation coming from a bulk. The Quantum Zeno effect happens because interactive measurements don't just observe a particle in the observed state, but actually "puts" the particle into that state (at least in the Copenhagen interpretation). So, repeated or continuous observations prevents the dispersion of the wave function, so it can't evolve very far from the state you last observed it in. Therefore, it stays in that state for as long as you keep observing it too quickly to let it evolve away from it
- if a computer measures the particle internally then instantly deletes results, does the effect happen? - what if the measurement is hashed ( no way to unencrypt it ) - what if a cat sees the measurement result in a closed room, then it's deleted, does the effect happen? I always wanted a physics lab to test these
Shrodinger hated cats and killed one by putting it in a box, and never opening it after. That's when he came up with the wonderful idea that says " if i never open the box, it's impossible to be sure that the cat is dead " only a probability. This way, in his sick sadistic twisted mind, he never felt guilty or felt like he did a bad thing because of the "uncertainty". Sadly, few people know the full story behind this psychopathic uncertainty principle..
If you are actually asking, my understanding is that all of these situations would constitute a real measurement in Quantum mechanics. It's less about a human being actually learning the measurement and more about a something physically interacting with the quantum system. It also gets into a physics law which says that information cannot be completely destroyed. Take your first example, even if a file is deleted from a computer, it leaves some physical changes that could in theory be used to reconstruct the original information.
On your "Think you understand Quantum Physics?" video, you mentioned that interaction-free measurement can not be used to violate the uncertainty principle, so the measurements will have limited accuracy. Yet they can still be used to prove this effect is real?
"Looking" is an interaction with the particle that causes it to become exactly one of the two allowed states. After we look, the wave function can mix the known state with the other state at a certain rate. When we look again, the mixed state will again become exactly one of the two allowed states and the two probabilities for the two states are directly determined by how much of "the other" state got mixed into the wave function. A short time interval between observations means it is VERY probable that the state will not change and shorter intervals results in more certainty that the state will not change. It is only after a long interval that the probability of changing becomes significant.
The prison analogue is pretty good, and watching the second state would be like watching the escape route instead of watching the cell. But I wonder why checking the second state does not interfere with the particle, when the particle is in a superposition between the two states the superposition will decoher the moment you check any state and for jumping from one state to another the particle would have to go through a superposition in between, so watching the second state actually prevents the particle from entering the superposition and therefore the particle has to remain in its cell state.
It can be kind of explained, though, by assuming the "hole," the second state the particle could slip into, isn't really nothing but also something that is affected by observation -- something that retains its previously known state if it interacts with a measurement and can only serve as a destination for the particle if it's left alone. Actually for all I know that might still come up, since I haven't watched the video to the end yet.
How is that surprising? The particles are described by probability distributions. Every time we observe it we reset the particles distribution. The longer we don't look the more uncertain we are about it's position or state or whatever it is we are measuring, and the higher the chances that it switches to another state. Therefore the more often we measure its state the more certain we are about its state. Every observation causes a wave collapse.
This is it right here, this is what I love so much. I love hearing the explanation of sa topic such as the zeno effect followed by "confirmed by experiments many times" . I get to sit comfortably in my new knowledge. I get that so rarely these days from the world.
I am no physicist, and there's a strong chance the explanation has been simplified in a way that makes this argument invalid but, I disagree with the premise that you can observe a particle's probability without interacting with it. If a particle would have a possibility of being in a certain quantum state, then its wavefunction **must** extend to that state, even if the probablility at the point you are interacting with s actually zero, so I don't believe there is a possibility of observing the negative space of a quantum state without interacting with it. [edit: had an extra word in there]
It's called an interaction-free measurement. Your mistake is thinking that because the wave-function is non-zero an interaction must have happened. If the wave-function is non-zero it just means that an interaction could have happened. If you didn't observe the particle, it didn't happen. Hence, interaction free.
@@SabineHossenfelder But if you check the lower state and the particle is not there, it still constitutes an interaction with the (wave-function of) the particle, right? The interaction forces the wave-function to change to zero probability for the lower state. That is not an interaction-free measurement.
The particle doesn't exist. So you are right -- one must interact with the thing that actually exists, aka the wave function. There is no way to observe the "negative space" of a quantum wave function, it's all part of the wave function. It seems paradoxical only because physicists keep insisting that the particle exists outside of measuring it. It does not. The particle isn't in both places at once. It doesn't exist at all! The wave function is the only thing that actually exists, and the problem is that when we measure it particles pop out and we don't know why.
I've always thought the mystery comes from the idea of the particle actually doing something, and that by watching it we somehow stop it. That isn't what's happening. The particle's state is not a result of something happening as we describe it in the macro world, rather an expression of probability, which we already know to be subjective depending on our knowledge of the system being studied. The more we know of a system in the macro world, the more certain are the probabilities of it being a certain way. That's inherent in the very definition of probability.
actually, you saved me. I was offended by 1 > 2, but since the whole thing is mod 2, it really said 1 > 0, and I can now fall asleep to Sabine videos and still respect myself in the morning, again.
Could you please explain how exactly we measured a particle without interacting with it? This really seems like the biggest not-explained-on-youtube question of this whole idea. I not sure how you can measure something without interacting with it in some way, unless it's a super macro definition of measure (for example, your measurement device is always running but you leave the room)
Hi NG. I think there was a suggestion to use a 3 energy level laser system of some kind, unlike the 2 level system in the video. What you do is take a bunch of atoms in the ground state, and shine an intense laser of the correct frequency to put the atoms in an excited state, a state that decays relatively slowly. Then you very rapidly pulse the atoms with another laser whose frequency will pump any atoms in the ground state to a 3rd (fast decaying) level. Then you look for fluorescence from that 3rd level. If there is no such fluorescence, then all the atoms are still in the original excited state, at least, in theory. These rapid pulse fluorescence measurement experiments apparently produce the Zeno effect in a laboratory. (Beige, et al, 1996)
Hi NG. I think your intuition is correct: you cannot measure anything without an interaction of some kind. A long time ago, I read some quantum Zeno stuff, and had some interactions with one of the authors. If memory serves, he suggested such things as measuring the polarization of light, using many very closely spaced polarized sheets as a (theoretical) way to produce the effect. That is, by observing the polarization of a mixed polarization beam, one could ‘freeze’ the polarization. [One would have to take the beam reduction from ‘lossy’ polarization sheets into account. Forgive me if I am misremembering his suggested experiment.]
This is such a pain in the right parietal lobe. When discussing spin or polarization, we face the question: "Is a particle inherently in an up or down state, or is it only in an up or down state when we measure it?" Then comes the follow-up: "If it stays in that state after measurement but then leaves for a while, why would it 'fall out' of that state later?" First, every part of an experiment, including the apparatus, has a magnetic field. Even though the walls of the box might be made of atoms with a neutral net magnetic field, there's still a field present. To complicate things further, every particle wobbles. So, how do you prove or disprove this hypothesis? It's quite a challenge, to say the least. But More distance = More Randomness, then Magnetic Field, More Time = More Randomness, then Wobble. So, if either time or distance has an effect, that is highly indicative... that my check that you are still reading my post has been proven positive.
Do you think it's possible this is some sort of acausal "anti-temporal" effect? I.E. the process of checking, even via the method that doesn't interact with the particle in a manner we would see as "directly" is preventing it from doing that BACKWARD through time? I wonder how you could even determine such a thing experimentally... I guess you would need some sort of non-temporal, time agnostic experiment? Is that even a thing one can do or is experimentation inherently reliant on causality and time? EDIT: I guess maybe you could do it if you just keep in mind the causal chain here is... wonky. EDIT EDIT: Interesting channel by the way.
Maybe to start with, a particle is inherently neither in an up or down state. In a quantum field just as space, there is no up or down, right or left, beginning or end. Your observation is an incorrect construct. Peace
@@gregoryrollins59 I agree, but I didn't have the time to explain that far. Up and down are based on the orientation of the original experiment. If you turned the experiment 90%, it could be left or right.
@@ZelosDomingo The time thing is a bit of an issue; I can't say either way. I am not saying what is right or wrong; what I can say is the most falsifiable way. This method assumes there is no wave function collapse. If you take that thought to the extreme, the electron or photon has already traveled through the entire experiment before you even detect it. So time here is a construct of our brain from our frame of reference, based on where we perceive the event (interaction between two particles) to have happened.
@TheNorgesOption it's like your question of why would it fall out of that state later. That's because up, down, left, and right are all the something at the same time. The particle might flip, but there is actually no direction. The particle is still the same. It's the old saying, same as above as below. No difference, even if it looks like there is.
The Zeno Effect feels like dealing with a 4 dimensional object i.e the thing exists in the 4th dimension and "pokes out" in to our perceived dimension at all point on in the probability field somewhat, but if you interact with it you're holding the sticking out part of it, but if you interact with the other spots, you're effectively blocking the 4th dimensional hole it could slip through. Of course if you blocked the path of an object it's not going to go anywhere, and if you hold it still it's not going to either, that feels intuitive, but if you don't know you're blocking or holding it, it won't make much sense why it's halted.
Great video as always. Recently began watching them but have you covered time-dependent quantum mechanics? Your audience should find it interesting for you to do a compare/contrast video of time- independent vs dependent QM.
Sabine is a hard worker and she is really dedicated to teaching science. She took the "people learn easier through visualisation thing" up imediately. For reasons of extremly bad health I am not sure how much longer I will hang around "here". But it sometimes gives me comfort to see that there are women so similar to me...that in some sense I still will be here after I left :)
@@Thomas-gk42 Our existence creates the illusion that time passes aka that things actually change. But it would be to complicated and to long here to explain how and why that happens
@@0NeverEverYes, I know, but anyway her view on the spritual consquences of that - SR, block universe, entropy complexity - she describes in her book, gave me a lot of hope. I wish you all the best.
@@Thomas-gk42 I have to admitt that I did not read that book. I thought as an atheist she thinks "nothing" comes after death (you are invited to correct me on that). I personally don't find nothingness scary. Especially if you compare it too the alternative of atheistic rebirth (yes such a thing is possible - if you think mind is a fundamental property nature) it has very soothing qualities. From my knowledge about physics and biology I have to logically exclude that we are our brain. My IQ is very high, and even so I am by fare not as good in every detail of physics as Sabine, there are some thinking errors in current pyhysics that are at a very fundamental level - you do not for example need to be able to calculate the math of relativity to see that the block universe creates strong logical problems. But if whatever you learned from Sabine is good for you mentally, than ignore me, and stick too it. Because we are all at our intelectual limits to answer questions about afterlife, the mind body problem etc. Even Genius as me, Sabine etc can and do make thinking errors. So have fear about something now, that might turn out untrue later on? Why, if there are several alternatives, are we forced to believe the most scarry? Do we have to proof by this that we are "cool" and fearless? Is that accidentaly a human vanity thing again... ;)
Some people in the comments seem to be confused about what "watching" or "observing" something means. It just means that it is entangled with something else, and that something can be a measuring apparatus.
5:16 How does the Zeno effect only happening under certain conditions make it any less mysterious? You said knowing the maths made it less mysterious but didn't talk about the math(s). Was it edited out?! Point claimed, but point not made. 🤨
1:36 So it is the same, that if we observe if the particle came to stage 2, because we are interfering with it too, as we do observing if is in stage 1? (by measuring if it come to stage 2 we are doing something to it)?
@@SabineHossenfelder We only have this set of mind to understand the universe! The one we inherited from our ancestors! That's why I hope so much in AI. It could have a different way of thinking, so it can help us with this! And then we must understand it too! Or the explanation would hide inside its "black box"? Thank you!
As many have said that interacting with the particle in any way means resetting it to state 1, my assumption here is that this effect would also work if you start all the particles on state 2 and check to see that they haven't switched to state 1. If the effect works both ways, then we know our observation isn't setting the state but instead is somehow blocking the action of switching states. Also food for thought - what if instead of directly measuring the particle we calculate its state by observing the results of interactions that it makes naturally? If the Zeno effect still holds true then we can't say that our observations are having any physical effect on the particle, unless it's somehow entangled with every single particle it interacts with.
Yes, and that would mean superdeterminism, right? Sabine is genius, showing here, how incomplete mainstream QM is. What is an observer, what a measurement, that's exactly what she's working on.
I take issue with the "prisoner escape" analogy, and the multiplication of probabilities. If you check on him after 2 hours, and he has not escaped, then the probability of him escaping in that first two hours does not figure in the subsequent calculation, at 4 hours. At 4 hours, the probability he has not escaped is STILL 75% (not .75 x .75 = 56%). If he escaped in the first 2 hours, you won't even be checking at 4 hours, because you already know he's not there. Yes, I am aware this is an analogy, and they will fail at some point, but that is not the problem here.
Perhaps always checking the state 2 apparatus (presumably by sending particles and energy there) affects the ability of the quantum particles under study from moving to state 2...? 🤔
Continues measurement always projects the state back to the eigenstates. The states are orthogonal and the projection is the dot product (cos of the angle). Taylor series for cos goes like 1-(x^2)/2... So for small angles it gives nearly 100% probability to get the original eigenstate again as a result.
The quantum zeno effect was first mentioned by Alan Turing in the 1950s, when apparently the physicists he spoke to scoffed at the effect, saying the notion of continuous measurement was unphysical.
I wish physicists would define what it means “to look at” or observe. Presumably, you can’t see quantum objects with the naked eye and photons are larger than atoms. So by observing a particle, they must be interacting with it meaning it’s not a passive observation like sitting in a coffee shop and watching pedestrians strolling past the window.
@oakpope there's no "photon size" exactly, but whatever measure you consider (usually wavelength) is indeed much larger than the atom. If you use visible light and not something like x-ray
But isn't that like saying I wish physicists would solve the "measurement problem" which remains possibly the greatest unsolved mystery of the universe and QM?
1:40 I feel this is an instance of "if 2 random variables are mutually exclusive, then they are NOT independent!". The fact that a particle is NOT in some state forces it to be in the other state(s).
The Quantum Zeno Effect, is a phenomenon in quantum mechanics where the time evolution of a quantum system can be slowed or "frozen" by frequent measurements. This effect is analogous to Zeno's arrow paradox, where an arrow in flight appears motionless when observed at each instant. In quantum systems, frequent measurement collapses the wavefunction repeatedly to its initial state, preventing transitions and effectively halting the system's evolution. This has been experimentally demonstrated with systems like ultracold atoms.
Yes, and that's exactly what Dr. Sabine's suggested experiments about superdeterminism are about.This comment section demonstrates, how ridiculous incomplete mainstream QM really is. She's such a foxy communicater😊
@@Thomas-gk42 Superdeterminism seeks to provide an alternative explanation for the foundations of quantum mechanics, while the Quantum Zeno Effect is an observed phenomenon within standard quantum mechanics. They are not competing explanations, but rather address different aspects of quantum theory. The Quantum Zeno Effect demonstrates how frequent measurements can influence quantum systems, effectively "freezing" their evolution. While Superdeterminism challenges the conventional understanding of measurement in quantum mechanics, suggesting that measurement outcomes are predetermined. Unlike the Quantum Zeno Effect, which has practical applications in quantum control, superdeterminism does not offer clear practical methods for manipulating quantum systems.
@@mickdonedee1 You are right of course. I just was reminded of Dr. Sabine´s proposals to test SD by very fast observations/measurements of entagled particles, what would provide a devianing outcome from the predictions of standard QM if SD is correct (it never was funded). But what the Q-Zeno-effect shows, is in my opinion, that the measurement process and the observer issue is not understood/described by standard QM/collaps-models, and therefore, a hidden variables solution is a realistic possibility.
@@Thomas-gk42 Superdeterminism postulates the existence of hidden variables, but these are not defined in terms of what they are supposed to be. Therefore, the assumption that "very fast observations/measurements of entagled particles" can provide more accurate outcomes than Quantum Mechanics is untestable. While the Quantum Zeno Effect does suggest a more complex picture of measurement than simple collapse models, it doesn't directly support hidden variable theories like superdeterminism. The effect can be explained within standard quantum mechanics and doesn't require the kind of predetermined correlations that superdeterminism proposes. The Zeno Effect adds nuance to our understanding of measurement in quantum mechanics, but it doesn't fundamentally challenge the core principles in the way that superdeterminism does. The Zeno effect highlights the role of environmental interactions in measurement, aligning more with decoherence theories than simple collapse models. Decoherence theory views measurement as a continuous process of coupling to the environment, rather than discrete collapse events. This aligns with the Zeno Effect's demonstration of how frequent measurements can inhibit quantum evolution. Venugopalan and Ghosh showed that the Zeno Effect experimental results are related to environment-induced decoherence, where the environment monitors some of the system's observables.
This is not how pots work. Beyond pots, when "resetting" a quantum particle, you're not resetting it, you're using a new one as the other particle will be gone into some kind of energy because it hit some indicator that enabled you to observe it. So it's not the same prisoner, it's a new prisoner every time you look.
Shouldn't the probabilities for the prisoner escaping be multiplicative instead of additive? For example if his chance of escaping is 12.5% per hour, then the chance of escaping in two hours is (1 - the chance of not escaping in 2 hours) = (1 - (0.875 * 0.875)) = (1 - 0.766) = 23.4%. And so on.
Well, in general it can be anything. If we assume that the prisoner has no memory and can simply decide to escape at any given moment independently of the past then the probability of NOT escaping becomes multiplicative. That's the Poisson process situation that Sabine talked about.
The Zeno effect also happens with Popeyes Fried Chicken. If I eat it every day for a week, there is an 80% chance that I will develop a serious case of indigestion. But if I eat every third day, the odds reset and I have about a 12% chance of indigestion. Somehow the Fried Chicken has a memory in my stomach.
Excuse me, but it seems that when dealing with this subject, it is helpful to define what counts as an “observation”, how it is implemented, and why the results can be attributed to it , instead of some other variable. Thank you
@@gerbre1Definitely seems (to me) that the hard sciences don't think like philosophers, and the soft sciences don't consider statistics in their papers.
1:39 - I don't find that weird at all. That state is part of what we should interpret as "the particle", whether it's there or not. It's like looking at the disconnected side of a switch - it's still part of the *switch,* even when it's not part of the *active circuit.* And, BTW, this whole behaviour is fully consistent with the kind of optimised behaviour you'd find in a computer simulation. I'm not saying this to claim that "reality is a computer simulation" (I don't think that statement has any useful meaning), just that analysing _how a computer simulation would do things_ is a very valid research avenue - probably more productive than just building bigger and bigger particle accelerators without even fully understanding what a "particle" actually *_is._*
If I understood correctly the wildest part is that if one sets up three states 1,2 and 3 in a way that going through state 2 is mandatory to get to the other states. Then set all particles to state 1 and only keep observing state 2. After a while one will find some particles in state 3 even when none were observed in state 2.
Are there any actual examples of this or is it just a math thing? Part of what makes quantum mechanics stuff feel so bunk is that its always "a particle" and never "an electron".
@@ASpaceOstrich Nope, not just a math thing. Sabine is describing the observable effects of physical tests that have been conducted to study the behavior of particles, without taking the time to describe the actual tests themselves. Also, just to clarify things a little more for you, there are many kinds of particles. An electron is classified as a particle, just as a photon is classified as a particle, assuming they are not in their waveform.
If the superposition is a third state, then surely looking where the particle is not is interacting with the superposition just as much as looking where the particle is.
That’s what I thought as well. Unrelated but What if we had people witnessing a superposition while we have their consciousness turned off, say under the effects of scoplamine or under a general anesthetic. We just set them up so they don’t need to make the decision to “look” at it
@@tonybalazs Yes, as you say interaction-free measurements look dumb to me. If you are not doing anything to the wave-function, then you believe in superdeterminism or other interpretations without superpositions.
@@placer7412 If they’re unconscious, I don’t think you can say that they witness it. If witnessing it (consciously) collapsed the wave function (for want of a better description) I imagine that failing to witness it when unconscious would also collapse it *as long as the same information passed from the superposition to either the conscious or the unconscious person*. This is because even if the person was unconscious, the collapsed state could have been detected.
You do realize that checking where the particle *isn't* is *still interacting* with that particle, right? You are just interacting with it *indirectly* . So, no, there's really nothing weird about the same thing happening when you interact with a particle *directly* or *indirectly* . You are *still interacting* with it, in both cases. It would actually be weird if *different* things happened in those two cases, because that would mean that the particle knew what you were doing, and chose (all by itself) to change its behavior based on that fact.
To me, quantum weirdness could look like an artifact of us living in a simulation. Prodding the simulation rules are bound to yield some hard-to-explain insights.
People treat the math that estimates the range where a quantum particle CAN be as the particle being in all the places it can be and snapping into place when watched. We don't change things by watching, unless we literally physically change them, we just don't know where they are unless we look.
Doesn't that show how incomplete established QM really is, ignoring these questions about the nature of an observer or a measurement. That's exactly what Sabine's research on superdeterminism is about.
Your prisoner/guard comparison doesn't jive in two ways. you mentioned: a particle has no memory. But also, the prisoner doesn't escape by equal chance/time. He's more likely to escape early (He's gone--this is my chance) and later (He's been gone so long, it's worth my trying now.).
Agreed. Still a good example to get across the idea of how probability of an event goes down as you watch (since watching has an effect - can't escape while being watched) to zero once watching constantly. Not weird for the prisoner example but weird for a particle that isn't interacted with to have this same transition in likelihood the more you watch it or the more you watch the other state. We would intuit that a particle would have the same probability of escaping regardless.
That you talk about "watching", while the paper cited writes "measurement-induced" puzzles me a lot. You can't see something without photons reaching your eyes, therefore you have to interact, right? It does not make that topic easier to digest for me when you say "watch" instead of "measure" - instead, it paints a wrong picture I'd say.
'That' is from your perspective, Mr. Observer@barrystock.Einstein.unv From my perspective, Sabine is filtered without a shirt into my fantasy universe.
This literally sounds like a software program. That if you aren't actively utilizing a module it will kill its process, then when you go to look it reinitialize (with the random effect being described). No it doesn't make sense at all that when you look at something that it behaves differently than when you don't. That defies all reasoning of the physical universe. That does sound natural at all. That sounds artificial. Either we have this *really* wrong, or this points to a higher power.
Who could ever believe that blasting a sample in high-intensity radiation to perform a measurement could have an effect on the sample. How wild. These quantum guys sure are dealing with a head scratcher. 🤯
@@adayah2933 the place where the particle is not is a nanometer away from where it IS. If you are blasting one area with anything, then an area that close is also being blasted. It's the same area.
Every particle is a little planet with little people on it who are watching through little telescopes to see if we are watching them (They can see our great big eyballs in the sky). This involves tiny little photons that are altogether indetectable except by tiny little people. I'll show myself out the woo-door. 🚪🚶.
Scrooge McDuck already knew that: You can only look at money if you can swim in it at the same time. And swimming in paper puts you in a bad mood, it has to glitter.
I would add to an anology with a guard and a prisoner: it's so happened that there's only one way outside of prison, so the guard may stand right outside, waiting for the prisoner to come out. But the prisoner just sits there inside the cell, even though from his perspective its the perfect time to try and escape. As if he has a 6th sense or accomplices or a way to sniff out the guard through the walls.
Disclaimer: I am not quantum or any physicist. Software developer who loves science. My understanding is that the "probability" of changing states comes from our inaccurate observations. Let me elaborate: It seems that human perception of time is sampled (or quantized?), we don't have the ability to truly observe something continuously. If we accept this then probability becomes something that we use to approximate the reality because of inability to make more precise observations. Say particle changes states every second, but scientists observe it with intervals of 2 seconds (because that is our limit for the purpose of demo). This will mean that our "continuous" observation will produce result which says that this particle is always in state 1. By stopping "continuous" observation and starting a new one on the odd number we may or may not discover that particle changed state to 2, and thus calculate that particle has some elaborate probability of changing state, when in objective reality it always changes states, only much faster than we can perceive... Well, the point is that not us nor our instruments are good enough (yet). In my opinion that is why probability is introduced in quantum mechanics, and maybe that is the best approximation we will ever have about how the world really works.
It may go a bit deeper in a physical sense. We have no reason to believe that the universe itself is capable of infinite accuracy. At physical resolutions approaching the planck scale we should expect to see real positional inaccuracy which we'd expect to show up as probabilistic outcomes.
@@Jesse_359 That's exactly what I am talking about. We also do not have a good reason to disbelieve it. All our knowledge based on observations (accurate as they may be) is used to build models which we use to subjectively reason about the workings of the objective universe. I really hope we continue to improve and will do better in the future
@@dimcha78 we have one real reason to expect that nature doesn't truck with infinities - they wreck probability. Positing a true physical infinity allows you to construct legitimate statements like 'everything happens everywhere at all times.' as a result of the irreducibility of infinities outside of the realm of mathematical abstraction.
For the prisoner example, when coming back and checking the 2nd time, the probability of him being there is still 75%. The 56% would require that you both did and didn’t check on him the first time; Did in order to reset his timer, didn’t in order to still have that first time give a 75% probability rather than a 100% one since you already know he didn’t escape.
I need to read more about the effect. I still do not get why some quantum objects have it while others do not. The ones I worked with (photons) do not have it. By the way, I studied physics apparently too early to have this in the curriculum.
Somehow similar to Michael Ende‘s Scheinriese (Pseudo giant). You can watch him, but his size will always never change, no matter where he moves to. It‘s like observing the object from a movie’s perspective, but you can’t go out to observe it in reality. Of course, this example - like Schrödingers cat - does not really catch the point. For those who don’t know, it may look nice at the first glance, but it’s nothing but just another wrong track on the long path to understanding. The good news: Other than that cat, the pseudo giant can never be messed up with a quantum object.. (:-).
I've seen the QZ effect explained _in seto_ in a very understandable way. The wave function can change a little bit over time, but each time you look at it, it's reset to one of the observable states. So, it's more like a baseball player trying to steal a base then a prisoner!
My apologies if these questions are dumb, Im still learning QM. 1) How fast is the collapse of the wave function? is it faster than C, can or has it been measure? 2) Can superposition and the subsequent collapse of the wave function be measured gravitationally? 3) Is it possible that retro-causality can cause the collapse of the wave function 4) is it observation or consciousness which causes the collapse of the wave function, have any experiments been conducted where an animal, such as a monkey to observe the outcome and react to the outcome ( a feedback system of rewards such as food etc given certain results, and conducted in a totally humane manner) what about an AI bot observing the collapse? 5) How many times can a particle go to super position and collapse the wave function and does the particle lose any engird in doing so?
Something seems off about the Zeno effect. I’ll have to see how this experiment is being conducted and this conclusion arrived at. The simple conclusion for me at this time would be that there is an interaction going on even when looking at where the particle “is not” thereby making any measurement dependent on the last.
I'll just post here my current understanding as some guy reading stuff but also curious on "observation"/"measurement": "Observation"/"measurement" is us "putting" some material "we can move and touch" in the setup so that when the particle/wave (we think) goes there, some indication (maybe something like a dot or a change in electric current reading I guess, etc.) appears and *we* can detect it. The "we can move and touch" is important here: interaction between individual particles (when we calculate in theory) are not considered as measurements. The double slit demonstrates the wackiness: single electrons 1) put dots in measuring plate, 2) put dots "everywhere" for some reason, but 3) after many electrons, the dots form that well-known interference pattern. Now the smarts among us developed the concept of wave function to explain 3), but the reasons of 1) and 2) are debated; the "why" of 1) is the "measurement problem" (if wave function of a single particle is physical, why it forms dot in the plate?).
So this explains why when I blink for a second during math class, my teacher had already filled the board with equations Ah I always knew that guy was in a superposition
I have the feeling that the example of radio-active decay is a bit misleading, in particular contrasting it with the transitions in a two-level system from the start of the video. In principle, there is not much of a conceptual difference between decay in a two-level system (e.g. an electronic excited state and the ground state in an atom), and radioactive decay. In the former case, the transition between the states is mediated by the electromagnetic interaction, and since the final state has vastly more phase space with an emitted photon in place, the time arrow follows from the entropy argument in the absence of thermal equilibrium with the electromagnetic field surrounding the atom, which is usually the case on earth with optical transitions of atoms. In the latter case, the transition between the states is mediated by for example the weak nuclear force. The only difference is that in the electromagnetic case, through the use of tunable lasers (providing high fluxes of the mediator of the electromagnetic interaction), we have powerful tools at our disposal to engineer the quantum measurement on the atom in a highly controllable manner. In the case of the decaying nucleus, we just can't probe the initial (or final) state of the nucleus directly in a comparable way as with the atom, but that's only for technical reasons, not for fundamental reasons (unless I misunderstand something about QED and QFT in general, which is totally possible). Then, secondly, the memorylessness and the fact that a vast ensemble of radio-active nuclei can be modelled with a Poisson process, resulting in a Poisson distribution of total counts during a finite time interval which importantly needs to be much shorter than the lifetime, has more to do with the size of the ensemble and the statistical independence of the emitters than with quantum measurement. As a matter of fact, a large ensemble of independent decaying two-level systems (from the start of the video) would show the exact same phenomenon (if you put a single-photon detector nearby, instead of directly probing the evolving quantum system(s) with an external light field)!
Wave function and its collapse should be the most studied subject in physics. It is such a fundamental phenomenon that we can only describe but we have no clue what it is...
No it shouldn't. "Wave function collapse" is an entirely classical phenomenon and entirely misses what makes quantum mechanics unique. People try to make it mysterious by calling it "wave function collapse" which gives you a mental image of a physical wave that is collapsing like a house of cards when perturbed. Yet, there is no reason at all to believe such a thing. The wave function is just a function for choosing a probability amplitude from a list of probability amplitudes, and this list is called the state vector. The state vector contains the likelihood of each event occurring. You update this vector when you acquire more information, and the update allows for it to be simplified ("reduced") because many of the amplitudes will be updated to zero. It is more accurately called the reduction of the state vector, which is also a feature in classical probability theory as you also update your probability distribution based on new observations which can allow for its simplification. This doesn't even have anything to do with quantum mechanics and the insistence that it is "mysterious" is based on a bunch of assumptions which are simply never justified, particularly that the state vector does not actually represent a list of probability amplitudes but instead the dimensions of a physical wave in an infinitely dimensional space that undergoes a physical collapse like a house of cards when perturbed. There is just no reason at all to believe that, nothing in the theory requires you to believe that. The infinitely dimensional nature of Hilbert space is again just something carried over from classical probability theory: the more events you are including in your model, the possible configuration of events grows exponentially, and so you need exponentially more probability amplitudes. A state vector for a single coin needs two probability amplitudes for the two possible outcomes, but for four coins it would need sixteen probability amplitudes for the sixteen possible outcomes. This is why the number of dimensions is unbounded and it has nothing to do with there literally physically existing an infinitely dimensional space whereby infinitely dimensional waves fluctuate. We know with certainty what the so-called "wave function collapse" is, it is nothing more than updating your prediction based on new information acquired, which is something you also do in classical statistical mechanics and is not even inherently "quantum" in nature. The people who insist it is mysterious make tons of entirely unjustified assumptions about what the wave function actually represents which they have no basis for other than wanting quantum mechanics to seem more mysterious than it actually is. Indeed, quantum mechanics differs drastically from classical mechanics, but not in the reduction of the state vector. Where it differs lies in the fact that probability amplitudes can be complex-valued which gives rise to interference effects, something which there is no analogue to in classical statistical mechanics.
So where do we begin? According to me, there’s more than one way to travel faster than light. One way is associated with wavelike behaviour, the other with particle-like behaviour. No need to be in any hurry to agree with me, but the answer is likely to be just as weird.
Well, I picked the challenge to put my finances in order. Then I invested in cryptocurrency,stocks,through the assistance of my discretionary fund manager,
If you are looking at where it isn't you are sending some energy to the spot where it isn't. If it was about to change to the other state it could almost get there then get the energy from the place it wasn't and switch back. Seems natural it would be at rest more where there is less energy. Hence, where you are not looking. An interesting experiment would be to have two places being looked at with different intensities of energy. Will it be in the place where there is less energy a larger percent of the time?
Sabine I have a question, maybe it can be a future podcast subject. While human consciousness seems to somehow effect a quantum state, has there ever been an experiment using non-human subjects like a dog, cat, or some other animal to see if their presence and gaze has the same effect?
How do you want to verify that? To verify it, you have to observe the whole quantum system including the dog, and so a huma being again is part of the observation. It's exactly what the "Wigner's friend" - though experiments are about.
Better illustrated using quantum tunnelling where the two states are symmetric energetically. You can then talk about normal modes and how observing any part of the well causes a "disturbance".
If you leave anything that can explore options with only 1 option, then sooner or later the one option is taken. By occupying the same Optional-Space via constant observation, the option is gone. So the zeno effect is just a hint, that quantum systems are in fact exploring possible options. The decay case is different in the sense that your observing the atoms surface and there are plenty of options for the decay to happen.
Please, Dr. Hossenfelder, do a video on what "observation" and "looks at" and "measure" mean in quantum mechanics. Obviously the universe didn't start acting differently when physicists were invented and started measuring things - non human quantum interactions must also have these same effects. What are they?
No disrespect to Dr Hossenfelder, but I personally wouldn’t seek her input regarding these issues (at least not authoritatively)
In fact I suspect she wouldn’t like hearing this notion, but this is an area of physics where the field of Philosophy can be credited with “de-obfuscating” the illegible mess that theorists left Quantum Mechanics. I mean, to the extent that physicists had actually addressed a lot of conceptual baggage that it was wallowing in, a simple question such as yours regarding these ridiculous descriptions of nature and what you were supposed to call whatever scientists were doing to nature (looking at it? measuring it? observing it?) would result in no consistency and very little progress on the conceptual domain.
Even worse was the fact many physicists who were interested in conceptual questions, or what is commonly recognized today as “the foundations of Quantum Mechanics” were straight up fired and blacklisted!
I highly recommend some of David Alberts talks or interviews where he discusses the way many careers were destroyed-like LITERALLY destroyed-for questioning the dogma of the standard Copenhagen interpretation of Quantum Mechanics
How can we be certain that the universe didn't act differently before we were here?
@@mrosskneOnce again, this is a somewhat more philosophical question, or at least a more foundational question that depends on an understanding of how knowledge and certainty interact in the scientific model.
You asked “how can we be certain …” and the scientific answer to that is always going to be “we can’t.” But for scientists, this is never a concern, because scientists aren’t interested in certainty, they are interested in probability.
So let’s ask this a different way: How can scientists make assumptions about how the universe acted in the past, given those assumptions are found to have an associated probability measure?
I find it puzzling how these effects involve a single particle, while being "observed", "watched" or "measured" requires interactions of gazzilion other particles. My lizzard brain can't get around this.
@@karelsmutny7038 I watched a video a while ago (I forget the name of the presenter) which explained that Shrodinger's wave equations were not wave equations in the true sense of the term but more closely resemble heat equations, which makes some sort of sense to me - thermodynamics being about the statistical properties of lots of little things interacting involving heat and entropy, and quantum mechanics being random or statistical, to some extent. So, perhaps observation of quantum events is like watching a kettle boil? They really do boil when watched (I've often repeated the experiment), but it does seem to take longer.
At age 12 (a long time ago, now), I disproved "a watched pot never boils". I'm not sure why I haven't received notice from the Nobel folks just yet, but I reckon the physics prize is wide open now.
You deserve recognition. Kids are brilliant 😜
Was that about the same time you proved that time does not fly?
Doing real physics is no longer the way to be nominated for a physics Nobel. I suggest you write some AI software.
@@yurinator4411
Time flies like an arrow.
Fruit flies like a banana.
Hope that helps ...
I´m currently solving the "Chicken and Egg" problem-
I've ordered both from Amazon -
I´ll let you know.
What hasn't been made clear is what are the special circumstances in a quantum system that constitutes its "memory" and results in the "Zeno effect"?
I am also wondering. For me a uranium core that could decay or not, seems to be a two state system similar to the first setup.
@@aarionsievo But that's the thing, is there really a "could" or is it actually a "must"?
It's an information constrained problem, a bit like the 'Monty Hall problem'. Maintaining a low entropy state by releasing information
I agree. This video left too much unexplained. What about her 2 state system had memory?
@@aarionsievo There is a very distinctive difference between a radioactive nuclei and the typical 2 level (but could be more states) System you use for the Quantum Zeno effect. You build a 2 level system that would rotate between the 2 states that starts in state 1. Then you continuously try to measure if it is in state 2 (you could also measure if in state 1, but that is less impressive and maybe more disruptive) and that keeps in in state 1, because a small rotation still give nearly 100% probability for the original state. The decay of the nuclei is not such a nice 2 level system. The decayed state is a multitude of states and usually better described like a macro state. In the principle description the non decayed state rotates into other states that than again rotate in further states and so on and so on (that is how decoherence happens in principle. Theoretically it could rotate back, but that only really happens for systems with very few states). And you would have to measure all the states that interact in first order with the non decayed state. And that is not possible.
I'm no quantum physicist, but this explains why my downloads freeze when I watch them.
funnily now that i have optical fiber, rarely i get a frozen download, i kinda watch all to see if some gives problems, but mostly to see hundreds of gigabytes downalod to my storage in minutes, not in weeks
Maybe you should get that third leg out of the way of the WiFi signal 😂
@@arch1107we are being scammed, ISPs are lazy and milking us for 10x the value giving us scraps. Vote to make ISPs a utility.
@@arch1107 You actually watch the interactions in the fiber cable? Or just the readings from your monitor.
🤣
The pot alone is not the problem, you need milk, too! Watched milk will not boil but look in the other direction for a second and your in for a long cleaning session on your induction stove!
is that why frogs never notice the boiling water because to them it is not boiling because thy were watching the pot the whole time
Ahah cause when you watch it you don’t let it go up too much
I cover my induction range top with towels, a tip from a chef. It's second-order wise to watch the cook and the wine supply instead of the pot.
@@rayzimmermin the story with boiling frog isnt true
@@jaroslavpesek6642 jokes online escape you don't thy
If you're checking state 2, you're doing something to it, and preventing that particle from going there. Measuring state 2 involves using a device that has some kind of current, which generates an electromagnetic field, which alters the local charge field in the experiment. but its not just a mathmatic field of numbers or some immaterial ether -- its a field of real photons with spin which effect the path of the particle not with magic or memory or time travel - but through physical bombardment.
They think pushing the interaction into a second order effect that they leave out of the model means it doesn't count.
I mean, if we assume collapse does happen for whatever reason and however it does (which I see no reason we shouldn't assume), I'd expect this to also work for the same reasons and roughly the same way. What I find interesting here is what this example might be able to say about such reasons and workings.
Like, could one calculate the effect and interactions as you describe to explain it, and would that work independently of how exactly the measurement is made? If not, does this point to some more "fundamental" properties for the collapse?
Anyway, sorry if I'm mostly rambling : p
This "checking of state 2" really needs clarifying for sure.
But how does state 2 interact with state 1? I guess we could do this experiment with entangled particles over a distance that doesn't allow physical interaction within the given timeframe.
No, you're not preventing the particle from moving to state 2. The Zeno effect was predicted and calculated before it was experimentally tested, and has been proven using multiple measurement techniques and methodologies.
The "memory" you're talking about is basically the particle being reset by the measuring interaction. I'm pretty sure you could do that with radioactivity, too, but then you'd need a measuring device that can actually interact with the particle without destroying it, and at those energies and such a small scale that's just not an option.
But the states aren't "places". If you're watching a particle to see if it's in state 2, but the particle is in state 1, you're still interacting with that particle.
I caught that too. Unless I'm missing something, then watching for state 2 of the particle *should* have the same effect as watching for state 1 because you're still observing the same particle, and I really hate the term observing because it introduces spooky psuedoscience like the particle is conscious and somehow aware of our attention which is not the case at all.
This is my opinion, as well. The act of measurement at either state 1 or 2 can have the sane overall effect on the particle.
The unfortunate aspect of QM is the sloppy and irregular language used. It tends to create false impressions and weird claims that don’t hold up well to a careful dissections of the facts.
Not necessarily. I'm sure the scientists thought of something that a video commenter - or three - thought of.
It's behaving as a wave, right? It's in both places and has a certain chance of being localized in either place.
@@damianGray I'm not a quantum physicist but what you are saying makes sense to me. How can one observe anything without changing the state from what it might have been if you had not observed it. Observation is a physical act. What is interesting about this is that we will never know what role consciousness plays in the Zeno effect. There are so many other things involved in the act of observing besides consciousness that no experiment could ever eliminate.
1:40 - "just check that the particle is not in state two" - well that is still interacting with the particle, so yeah, there's no such thing as measurement independence when working with quantum effects. I don't understand what's different here than just saying that an observation is an interaction, and an interaction effects the state of the system.
How is that interacting with the particle though?
The elephant in the room is that the whole of science is based - whether it is aware of it or not - on the basis of the godlike 'detached observer' who measures, but never affects.
That's why quantum physics rapidly becomes unintelligible to people talking in terms of classical notions like 'observable universe' etc etc.
@@Ajay-kz9ns When you look at a thing in the macro world, photons hit it and it sends photons back to your eyeball, but the photons usually don't have much effect on the thing you are looking at. In the quantum world when you "look" at a particle, just one photon (or any other particle) can change the state of the particle being observed, so the only way to observe a particle is to interact with it.
@@doubletribble-yt when you look at something you aren't shooting photons out of your eyes though, you are just receiving photons that were heading towards you anyway right? Or is this more a consequence of needing to specifically shoot a photon or particle at another in order to get your screen blip telling you which state it is in because you can't actually see a quantum particle with the naked eye?
my question is: are we sure that when we observe if the 2nd state wasn't reached, we aren't also interacting with the 1st state?
Like for example, checking the 2nd state 'fills it in' which makes it impossible for the quantum whatnot in the 1st state to move.
If you're checking state 2, then you are necessarily checking state 1 (given the situation where the thing you are looking for must be in one of those two states.)
good point
The experiment should be devised so that the test subject is free to move into any state with an equal probability. It doesn't really matter that you are choosing the 2nd state over the first. The measurement "locks in" that value for that "round" of the experiment. That is why it gives these "spooky" results. Its a red herring anyway because what the "zeno effect" is really measuring is the probability over a given time, not that the probability goes up over time. To see the true probability distribution think of a pinball machine that has multiple targets, once it bounces off the first it resets and can hit another, but the score accumulates.
@mrmouse4121 No one talks about the underlying metric of reality supporting both the existence of the.'particle' and the 'states', in terms of degrees of freedom...
@@obsidianjane4413 I fear that I don't understand enough physics to be able to interact with quantum in a manner that isn't metaphors and analogies. Which quickly devolves into wrong assumptions which are a pain to unlearn- especially with a subject that is so far from what humans are used to observe.
Around 1:48 you're still interacting with the system even if you're only checking where the particle isn't. Claiming this is weird is akin to placing a detector at only one slit in a double-slit experiment, then acting surprised you have a clump pattern behind both slits.
Why would a detector at one slit affect the other?
@@mrosskne because the particle is a wave, and measuring where it could be and finding it's not there is interacting with the wave, which causes a collapse
@@meiskam The particle is not a wave, only its most likely position.
Petition to make physicists stop using words like "observing" and "looking at" in context of explaining Quantum Mechanics to regular audiences. Just say "interacting", or "literally bombarding it with other particles" to make it all less spooky. You people are never simply looking at something anymore than a tree is looking at a car wrapped around it next to the highway.
Sorry it's strange regardless of words used. And it is certainly fine to say Observe, when that is what we are doing even if it's not with our eyes, just as people observe the world with multiple senses, so do the scientists observe via various methods.
She explicitly noted it's not about direct interaction, you can observe the "empty slot at state 2" and that will keep the particle at state 1 without interacting with it directly.
@thedeemon but you're interacting with the only other possible state it could be in, possibly blocking movement
THANK YOU. It's almost like it's intentional...
@@franesustic988no it's not. It like studying a rare nocturnal buttefly with a flamethrower and wondering why they're look...and smell, different than you expected
"watching" a radioactive decay is diffrent than "watching" an ultracold lattice gas (the paper mentioned) -- if by "watching" a radioactive decay we mean looking at a Geiger counter. The Geiger counter goes off *after* the decay has already happened, it doesn't interact with the radioactive atom. But "watching" the ultracold gas does involve interacting with it. If we had some way of measuring the state of the radioactive atom directly, then we could perhaps have a zeno effect (or anti-zeno effect .. speeding up the decay).
I also thnk it's not fair to talk about the memory-less-ness of radioactivity. That is true if you have many atoms that you are "looking at". But each individual atom can only decay once (so we can't speak of memory .. once it has decayed, that particular atom won't decay anymore). I think the fair comparison is between a single radioactive atom that can decay, and the thought experiment atom with levels 1 and 2. Then, they are in fact the same kind of system -- but the difference is the assumed measurements being done in each case, as mentiond in my original post.
As I understand it, memorylessness is a property of a probability distribution such as the exponential distribution, which radioactive decay obeys. If I understand correctly, a subatomic particle has NO physical way of storing the information ”for how long time have I still not decayed”, therefore it must obey exponential distribution and zeno effect will never work on it. The superposition states where zeno effect can work seem to require some other, special kind of a propability distribution that is able to ”gain progress” over time, evolving towards state 2 over time, and if it is observed at state 1, then its ”progress” and wave function is reset. Even if we would look at a subatomic particle directly to see if it’s decayed or not, that’s a different case, because in that specific probability distribution there is no ”progress” to reset - radioactivity distribution is simply some constant probability per infinitesimal time to decay.
@@maxsamarin9002original paper was about how zeno effect leads to deviation from exponential decay law. Basically, the law is an approximation if your observation period is much bigger that time evolution of state. Quantum states evolves very fast, so you see effect only if observe system extremely often.
There was serious criticism to experiments with cold atoms 10 years ago. Basically, probably they didn't show zeno effect. One part of criticism was exactly what you said. Maybe I'm BSing now, but according my impression, there is no established good experiment that undoubtedly demonstrated zeno effect.
This sounds perfectly in line with the measurement apparatus getting entangled with the experiment during the measurement. Before the measurement the particle is in a superposition of state 1 and 2. After measuring it once, the whole setup is now in the superposition of (1, we've measured 1) and (2, we've measured 2).
Now if we only consider the first part of the superposition, after a while it will shift to a superposition of (1, we've measured 1) and (2, we've measured 1) and if we measure it once more, we will again get a superposition of (1, we've measured 1 and 1) and (2, we've measured 1 and 2).
The "paradox" occurs because 1) as you said in the video, the probability density of the state changing starts at 0 and only increases after the measurement and 2) our measurement apparatus is not isolated from our bodies and so we're getting entangled with the "almost certainly 1" states as they are measured (or the wave function collapses, if that's how you prefer to think about it).
You can watch pots boil. Just need enough heat to melt them first.
I was gonna say, you have to put some water in it first!
If you shortly observe the system for the state 2, you observed it and influenced it, resetting the "timer". It would only be the strange if you expect some particle ending up at some isolated position, and particle never gets there because you frequently check if the particle is there.
As for the prison guard and prisoner analogy, it would be like if the prison guard is checking outside of the prison if the prisoner is trying to escape. And strangly, he never tries to escape because guard is looking outside, but the prisoner cannot know if the guard is looking outside. It would only be strange if quantum systems would behave like that.
The important difference with radioactive decay is that you're not actually observing - and interacting with - individual nuclear states. You're just catching radiation coming from a bulk. The Quantum Zeno effect happens because interactive measurements don't just observe a particle in the observed state, but actually "puts" the particle into that state (at least in the Copenhagen interpretation). So, repeated or continuous observations prevents the dispersion of the wave function, so it can't evolve very far from the state you last observed it in. Therefore, it stays in that state for as long as you keep observing it too quickly to let it evolve away from it
- if a computer measures the particle internally then instantly deletes results, does the effect happen?
- what if the measurement is hashed ( no way to unencrypt it )
- what if a cat sees the measurement result in a closed room, then it's deleted, does the effect happen?
I always wanted a physics lab to test these
Yes, and that are the experiments, Dr. Sabine suggests since years, and never were funded.
Shrodinger hated cats and killed one by putting it in a box, and never opening it after.
That's when he came up with the wonderful idea that says " if i never open the box, it's impossible to be sure that the cat is dead " only a probability.
This way, in his sick sadistic twisted mind, he never felt guilty or felt like he did a bad thing because of the "uncertainty".
Sadly, few people know the full story behind this psychopathic uncertainty principle..
If you are actually asking, my understanding is that all of these situations would constitute a real measurement in Quantum mechanics. It's less about a human being actually learning the measurement and more about a something physically interacting with the quantum system.
It also gets into a physics law which says that information cannot be completely destroyed. Take your first example, even if a file is deleted from a computer, it leaves some physical changes that could in theory be used to reconstruct the original information.
On your "Think you understand Quantum Physics?" video, you mentioned that interaction-free measurement can not be used to violate the uncertainty principle, so the measurements will have limited accuracy. Yet they can still be used to prove this effect is real?
How do you measure anything without interacting with it?
"Looking" is an interaction with the particle that causes it to become exactly one of the two allowed states. After we look, the wave function can mix the known state with the other state at a certain rate. When we look again, the mixed state will again become exactly one of the two allowed states and the two probabilities for the two states are directly determined by how much of "the other" state got mixed into the wave function. A short time interval between observations means it is VERY probable that the state will not change and shorter intervals results in more certainty that the state will not change. It is only after a long interval that the probability of changing becomes significant.
The prison analogue is pretty good, and watching the second state would be like watching the escape route instead of watching the cell. But I wonder why checking the second state does not interfere with the particle, when the particle is in a superposition between the two states the superposition will decoher the moment you check any state and for jumping from one state to another the particle would have to go through a superposition in between, so watching the second state actually prevents the particle from entering the superposition and therefore the particle has to remain in its cell state.
For some prisoners in the U.S. with previous relationships to big wigs and underage girls, the probability of suicide goes to 100%
This is the part of the analogy that I thought was coming but never happened, that is, watching the escape route instead of the prisoner directly.
It can be kind of explained, though, by assuming the "hole," the second state the particle could slip into, isn't really nothing but also something that is affected by observation -- something that retains its previously known state if it interacts with a measurement and can only serve as a destination for the particle if it's left alone.
Actually for all I know that might still come up, since I haven't watched the video to the end yet.
How is that surprising?
The particles are described by probability distributions. Every time we observe it we reset the particles distribution. The longer we don't look the more uncertain we are about it's position or state or whatever it is we are measuring, and the higher the chances that it switches to another state. Therefore the more often we measure its state the more certain we are about its state.
Every observation causes a wave collapse.
This is it right here, this is what I love so much. I love hearing the explanation of sa topic such as the zeno effect followed by "confirmed by experiments many times" . I get to sit comfortably in my new knowledge. I get that so rarely these days from the world.
I am no physicist, and there's a strong chance the explanation has been simplified in a way that makes this argument invalid but,
I disagree with the premise that you can observe a particle's probability without interacting with it.
If a particle would have a possibility of being in a certain quantum state, then its wavefunction **must** extend to that state, even if the probablility at the point you are interacting with s actually zero, so I don't believe there is a possibility of observing the negative space of a quantum state without interacting with it.
[edit: had an extra word in there]
It's called an interaction-free measurement. Your mistake is thinking that because the wave-function is non-zero an interaction must have happened. If the wave-function is non-zero it just means that an interaction could have happened. If you didn't observe the particle, it didn't happen. Hence, interaction free.
@@SabineHossenfelder But if you check the lower state and the particle is not there, it still constitutes an interaction with the (wave-function of) the particle, right? The interaction forces the wave-function to change to zero probability for the lower state. That is not an interaction-free measurement.
@@SabineHossenfelderwell explained, thank you
The particle doesn't exist. So you are right -- one must interact with the thing that actually exists, aka the wave function. There is no way to observe the "negative space" of a quantum wave function, it's all part of the wave function. It seems paradoxical only because physicists keep insisting that the particle exists outside of measuring it. It does not. The particle isn't in both places at once. It doesn't exist at all! The wave function is the only thing that actually exists, and the problem is that when we measure it particles pop out and we don't know why.
I don't think it is possible for any experiment to be performed without some sort of interaction between apparatus and particles.
I've always thought the mystery comes from the idea of the particle actually doing something, and that by watching it we somehow stop it. That isn't what's happening. The particle's state is not a result of something happening as we describe it in the macro world, rather an expression of probability, which we already know to be subjective depending on our knowledge of the system being studied. The more we know of a system in the macro world, the more certain are the probabilities of it being a certain way. That's inherent in the very definition of probability.
As a software engineer, I feel completely disrespected by the use of 1,2 instead of 0,1 for the hypothetical quantum states
Quantum computing people do
Our local railway station has a platform 0, which makes me feel software engineering is vindicated.
actually, you saved me. I was offended by 1 > 2, but since the whole thing is mod 2, it really said 1 > 0, and I can now fall asleep to Sabine videos and still respect myself in the morning, again.
i was upset it wasnt up and down. no idea why i am an earth scientist not a physicist
@@thamalupiyadigama1216 In my uni the quantum computing courses still used 0, 1. I'm not saying its more correct though, just mentioning.
Could you please explain how exactly we measured a particle without interacting with it?
This really seems like the biggest not-explained-on-youtube question of this whole idea. I not sure how you can measure something without interacting with it in some way, unless it's a super macro definition of measure (for example, your measurement device is always running but you leave the room)
Even in that case, the measurement device is interacting. Interaction doesn't require a human.
Hi NG. I think there was a suggestion to use a 3 energy level laser system of some kind, unlike the 2 level system in the video. What you do is take a bunch of atoms in the ground state, and shine an intense laser of the correct frequency to put the atoms in an excited state, a state that decays relatively slowly. Then you very rapidly pulse the atoms with another laser whose frequency will pump any atoms in the ground state to a 3rd (fast decaying) level. Then you look for fluorescence from that 3rd level. If there is no such fluorescence, then all the atoms are still in the original excited state, at least, in theory. These rapid pulse fluorescence measurement experiments apparently produce the Zeno effect in a laboratory. (Beige, et al, 1996)
Hi NG. I think your intuition is correct: you cannot measure anything without an interaction of some kind. A long time ago, I read some quantum Zeno stuff, and had some interactions with one of the authors. If memory serves, he suggested such things as measuring the polarization of light, using many very closely spaced polarized sheets as a (theoretical) way to produce the effect. That is, by observing the polarization of a mixed polarization beam, one could ‘freeze’ the polarization. [One would have to take the beam reduction from ‘lossy’ polarization sheets into account. Forgive me if I am misremembering his suggested experiment.]
This is such a pain in the right parietal lobe. When discussing spin or polarization, we face the question: "Is a particle inherently in an up or down state, or is it only in an up or down state when we measure it?" Then comes the follow-up: "If it stays in that state after measurement but then leaves for a while, why would it 'fall out' of that state later?" First, every part of an experiment, including the apparatus, has a magnetic field. Even though the walls of the box might be made of atoms with a neutral net magnetic field, there's still a field present. To complicate things further, every particle wobbles. So, how do you prove or disprove this hypothesis? It's quite a challenge, to say the least. But More distance = More Randomness, then Magnetic Field, More Time = More Randomness, then Wobble. So, if either time or distance has an effect, that is highly indicative... that my check that you are still reading my post has been proven positive.
Do you think it's possible this is some sort of acausal "anti-temporal" effect? I.E. the process of checking, even via the method that doesn't interact with the particle in a manner we would see as "directly" is preventing it from doing that BACKWARD through time? I wonder how you could even determine such a thing experimentally... I guess you would need some sort of non-temporal, time agnostic experiment? Is that even a thing one can do or is experimentation inherently reliant on causality and time?
EDIT: I guess maybe you could do it if you just keep in mind the causal chain here is... wonky.
EDIT EDIT: Interesting channel by the way.
Maybe to start with, a particle is inherently neither in an up or down state. In a quantum field just as space, there is no up or down, right or left, beginning or end. Your observation is an incorrect construct.
Peace
@@gregoryrollins59 I agree, but I didn't have the time to explain that far. Up and down are based on the orientation of the original experiment. If you turned the experiment 90%, it could be left or right.
@@ZelosDomingo The time thing is a bit of an issue; I can't say either way. I am not saying what is right or wrong; what I can say is the most falsifiable way. This method assumes there is no wave function collapse. If you take that thought to the extreme, the electron or photon has already traveled through the entire experiment before you even detect it. So time here is a construct of our brain from our frame of reference, based on where we perceive the event (interaction between two particles) to have happened.
@TheNorgesOption it's like your question of why would it fall out of that state later. That's because up, down, left, and right are all the something at the same time. The particle might flip, but there is actually no direction. The particle is still the same. It's the old saying, same as above as below. No difference, even if it looks like there is.
The Zeno Effect feels like dealing with a 4 dimensional object i.e the thing exists in the 4th dimension and "pokes out" in to our perceived dimension at all point on in the probability field somewhat, but if you interact with it you're holding the sticking out part of it, but if you interact with the other spots, you're effectively blocking the 4th dimensional hole it could slip through.
Of course if you blocked the path of an object it's not going to go anywhere, and if you hold it still it's not going to either, that feels intuitive, but if you don't know you're blocking or holding it, it won't make much sense why it's halted.
Great video as always. Recently began watching them but have you covered time-dependent quantum mechanics? Your audience should find it interesting for you to do a compare/contrast video of time- independent vs dependent QM.
Sabine, could you release a companion video with a bit more details on experimental setups used to perform experiments mentioned in this video?
Sabine is a hard worker and she is really dedicated to teaching science. She took the "people learn easier through visualisation thing" up imediately. For reasons of extremly bad health I am not sure how much longer I will hang around "here". But it sometimes gives me comfort to see that there are women so similar to me...that in some sense I still will be here after I left :)
🌺Thank you for your wonderful words. "Our existence transcends the passage of time" -- Sabine Hossenfelder, physicist
Sending you peace and love ❤
@@Thomas-gk42 Our existence creates the illusion that time passes aka that things actually change. But it would be to complicated and to long here to explain how and why that happens
@@0NeverEverYes, I know, but anyway her view on the spritual consquences of that - SR, block universe, entropy complexity - she describes in her book, gave me a lot of hope. I wish you all the best.
@@Thomas-gk42 I have to admitt that I did not read that book. I thought as an atheist she thinks "nothing" comes after death (you are invited to correct me on that). I personally don't find nothingness scary. Especially if you compare it too the alternative of atheistic rebirth (yes such a thing is possible - if you think mind is a fundamental property nature) it has very soothing qualities. From my knowledge about physics and biology I have to logically exclude that we are our brain. My IQ is very high, and even so I am by fare not as good in every detail of physics as Sabine, there are some thinking errors in current pyhysics that are at a very fundamental level - you do not for example need to be able to calculate the math of relativity to see that the block universe creates strong logical problems. But if whatever you learned from Sabine is good for you mentally, than ignore me, and stick too it. Because we are all at our intelectual limits to answer questions about afterlife, the mind body problem etc. Even Genius as me, Sabine etc can and do make thinking errors. So have fear about something now, that might turn out untrue later on? Why, if there are several alternatives, are we forced to believe the most scarry? Do we have to proof by this that we are "cool" and fearless? Is that accidentaly a human vanity thing again... ;)
Some people in the comments seem to be confused about what "watching" or "observing" something means. It just means that it is entangled with something else, and that something can be a measuring apparatus.
Wheeler's 'It from bit' makes more and more sense with every new thing I hear about.
Keep shining! Your work is outstanding!
5:16 How does the Zeno effect only happening under certain conditions make it any less mysterious? You said knowing the maths made it less mysterious but didn't talk about the math(s). Was it edited out?! Point claimed, but point not made. 🤨
Fake science only make claims, not points.
It´s in the maths, I estimate, but who in her audience can understand it...
@@Thomas-gk42 Even so, her claim was apropos of nothing, and I'm sure that she would not want us to believe it just because she said so. :-)
Just ask Pias
@@Thomas-gk42👻👽
The quantum xeno affect reminds me of the Monty Hall problem. Bro counter intuitive probabilities
That was clear as buttermilk
I think they are wrong.
I saw Sabine in an article on my new tab screen from El Pais! How neat to see her out in the wild.
1:36 So it is the same, that if we observe if the particle came to stage 2, because we are interfering with it too, as we do observing if is in stage 1?
(by measuring if it come to stage 2 we are doing something to it)?
Yes, unless there is something else going on that makes a difference between the two (like one being coupled to something else).
@@SabineHossenfelder We only have this set of mind to understand the universe! The one we inherited from our ancestors!
That's why I hope so much in AI. It could have a different way of thinking, so it can help us with this!
And then we must understand it too!
Or the explanation would hide inside its "black box"?
Thank you!
As many have said that interacting with the particle in any way means resetting it to state 1, my assumption here is that this effect would also work if you start all the particles on state 2 and check to see that they haven't switched to state 1. If the effect works both ways, then we know our observation isn't setting the state but instead is somehow blocking the action of switching states. Also food for thought - what if instead of directly measuring the particle we calculate its state by observing the results of interactions that it makes naturally? If the Zeno effect still holds true then we can't say that our observations are having any physical effect on the particle, unless it's somehow entangled with every single particle it interacts with.
Yes, and that would mean superdeterminism, right? Sabine is genius, showing here, how incomplete mainstream QM is. What is an observer, what a measurement, that's exactly what she's working on.
Quantum particle: 'feels uneasy while being observed'
Me: 'feels uneasy that a%×b%=a×b% and not a×b%^2 ' 😅😅
QM is so incomplete 😉
I take issue with the "prisoner escape" analogy, and the multiplication of probabilities. If you check on him after 2 hours, and he has not escaped, then the probability of him escaping in that first two hours does not figure in the subsequent calculation, at 4 hours. At 4 hours, the probability he has not escaped is STILL 75% (not .75 x .75 = 56%). If he escaped in the first 2 hours, you won't even be checking at 4 hours, because you already know he's not there. Yes, I am aware this is an analogy, and they will fail at some point, but that is not the problem here.
Perhaps always checking the state 2 apparatus (presumably by sending particles and energy there) affects the ability of the quantum particles under study from moving to state 2...? 🤔
Continues measurement always projects the state back to the eigenstates. The states are orthogonal and the projection is the dot product (cos of the angle). Taylor series for cos goes like 1-(x^2)/2... So for small angles it gives nearly 100% probability to get the original eigenstate again as a result.
The quantum zeno effect was first mentioned by Alan Turing in the 1950s, when apparently the physicists he spoke to scoffed at the effect, saying the notion of continuous measurement was unphysical.
I wish physicists would define what it means “to look at” or observe. Presumably, you can’t see quantum objects with the naked eye and photons are larger than atoms. So by observing a particle, they must be interacting with it meaning it’s not a passive observation like sitting in a coffee shop and watching pedestrians strolling past the window.
"photons are larger than atoms" hum ?
Exactly,I was thinking the same thing. By “observing” it seems like you’d have to introduce energy into the system to “see” the state of the particle
@oakpope there's no "photon size" exactly, but whatever measure you consider (usually wavelength) is indeed much larger than the atom. If you use visible light and not something like x-ray
The photon is the particle state of light which is larger than an electron. An electron microscope can “see “ things with higher resolution
But isn't that like saying I wish physicists would solve the "measurement problem" which remains possibly the greatest unsolved mystery of the universe and QM?
1:40 I feel this is an instance of "if 2 random variables are mutually exclusive, then they are NOT independent!". The fact that a particle is NOT in some state forces it to be in the other state(s).
Thanks for having a take on this topic, which I suggested some months ago. Happy to hear about your view on the topic.
Yes, you did! Thanks again!
@@SabineHossenfelder ☺
What did you understand? please help me to understand it too.
The Quantum Zeno Effect, is a phenomenon in quantum mechanics where the time evolution of a quantum system can be slowed or "frozen" by frequent measurements. This effect is analogous to Zeno's arrow paradox, where an arrow in flight appears motionless when observed at each instant. In quantum systems, frequent measurement collapses the wavefunction repeatedly to its initial state, preventing transitions and effectively halting the system's evolution. This has been experimentally demonstrated with systems like ultracold atoms.
Yes, and that's exactly what Dr. Sabine's suggested experiments about superdeterminism are about.This comment section demonstrates, how ridiculous incomplete mainstream QM really is. She's such a foxy communicater😊
@@Thomas-gk42 Superdeterminism seeks to provide an alternative explanation for the foundations of quantum mechanics, while the Quantum Zeno Effect is an observed phenomenon within standard quantum mechanics. They are not competing explanations, but rather address different aspects of quantum theory.
The Quantum Zeno Effect demonstrates how frequent measurements can influence quantum systems, effectively "freezing" their evolution. While Superdeterminism challenges the conventional understanding of measurement in quantum mechanics, suggesting that measurement outcomes are predetermined.
Unlike the Quantum Zeno Effect, which has practical applications in quantum control, superdeterminism does not offer clear practical methods for manipulating quantum systems.
@@mickdonedee1 You are right of course. I just was reminded of Dr. Sabine´s proposals to test SD by very fast observations/measurements of entagled particles, what would provide a devianing outcome from the predictions of standard QM if SD is correct (it never was funded). But what the Q-Zeno-effect shows, is in my opinion, that the measurement process and the observer issue is not understood/described by standard QM/collaps-models, and therefore, a hidden variables solution is a realistic possibility.
@@Thomas-gk42 Superdeterminism postulates the existence of hidden variables, but these are not defined in terms of what they are supposed to be. Therefore, the assumption that "very fast observations/measurements of entagled particles" can provide more accurate outcomes than Quantum Mechanics is untestable.
While the Quantum Zeno Effect does suggest a more complex picture of measurement than simple collapse models, it doesn't directly support hidden variable theories like superdeterminism. The effect can be explained within standard quantum mechanics and doesn't require the kind of predetermined correlations that superdeterminism proposes. The Zeno Effect adds nuance to our understanding of measurement in quantum mechanics, but it doesn't fundamentally challenge the core principles in the way that superdeterminism does.
The Zeno effect highlights the role of environmental interactions in measurement, aligning more with decoherence theories than simple collapse models.
Decoherence theory views measurement as a continuous process of coupling to the environment, rather than discrete collapse events. This aligns with the Zeno Effect's demonstration of how frequent measurements can inhibit quantum evolution. Venugopalan and Ghosh showed that the Zeno Effect experimental results are related to environment-induced decoherence, where the environment monitors some of the system's observables.
@@mickdonedee1 🙂thanks for your explanation.
🧀🥀
This is not how pots work. Beyond pots, when "resetting" a quantum particle, you're not resetting it, you're using a new one as the other particle will be gone into some kind of energy because it hit some indicator that enabled you to observe it. So it's not the same prisoner, it's a new prisoner every time you look.
Shouldn't the probabilities for the prisoner escaping be multiplicative instead of additive? For example if his chance of escaping is 12.5% per hour, then the chance of escaping in two hours is (1 - the chance of not escaping in 2 hours) = (1 - (0.875 * 0.875)) = (1 - 0.766) = 23.4%. And so on.
Well, in general it can be anything. If we assume that the prisoner has no memory and can simply decide to escape at any given moment independently of the past then the probability of NOT escaping becomes multiplicative. That's the Poisson process situation that Sabine talked about.
This explains why TV stayed on the wall during this whole video, but when I went to the bathroom, it raided the refrigerator.
The Zeno effect also happens with Popeyes Fried Chicken. If I eat it every day for a week, there is an 80% chance that I will develop a serious case of indigestion. But if I eat every third day, the odds reset and I have about a 12% chance of indigestion. Somehow the Fried Chicken has a memory in my stomach.
What the cluck 😉
@@SwanRonsonDonnyJepp 0.8/3 is about 26.7% but it is like filling a bucket that has a hole in it then trying to measure how much.
Beginner question: How is "observe" defined? When is something observed, when it isn't?
Excuse me, but it seems that when dealing with this subject, it is helpful to define what counts as an “observation”, how it is implemented, and why the results can be attributed to it , instead of some other variable. Thank you
It seems that physicists don't know what defines an observation or measurement.
@@gerbre1Definitely seems (to me) that the hard sciences don't think like philosophers, and the soft sciences don't consider statistics in their papers.
Poisson distrubution always have had a funny ringing to my ears since poisson means fish in french.
Leave the door open, give him five bucks, and take a day off. When you return,
He's in his cell eating ice cream with the door open.
Where can I check in?😂
Your course sounds very interesting.
1:39 - I don't find that weird at all. That state is part of what we should interpret as "the particle", whether it's there or not. It's like looking at the disconnected side of a switch - it's still part of the *switch,* even when it's not part of the *active circuit.*
And, BTW, this whole behaviour is fully consistent with the kind of optimised behaviour you'd find in a computer simulation. I'm not saying this to claim that "reality is a computer simulation" (I don't think that statement has any useful meaning), just that analysing _how a computer simulation would do things_ is a very valid research avenue - probably more productive than just building bigger and bigger particle accelerators without even fully understanding what a "particle" actually *_is._*
If I understood correctly the wildest part is that if one sets up three states 1,2 and 3 in a way that going through state 2 is mandatory to get to the other states.
Then set all particles to state 1 and only keep observing state 2. After a while one will find some particles in state 3 even when none were observed in state 2.
Are there any actual examples of this or is it just a math thing? Part of what makes quantum mechanics stuff feel so bunk is that its always "a particle" and never "an electron".
@@ASpaceOstrich Nope, not just a math thing. Sabine is describing the observable effects of physical tests that have been conducted to study the behavior of particles, without taking the time to describe the actual tests themselves. Also, just to clarify things a little more for you, there are many kinds of particles. An electron is classified as a particle, just as a photon is classified as a particle, assuming they are not in their waveform.
If the superposition is a third state, then surely looking where the particle is not is interacting with the superposition just as much as looking where the particle is.
Does this relate to the “interaction-free measurement” (Quiat et al.) paper you mention in your “bomb” video?
That’s what I thought as well.
Unrelated but What if we had people witnessing a superposition while we have their consciousness turned off, say under the effects of scoplamine or under a general anesthetic. We just set them up so they don’t need to make the decision to “look” at it
@@tonybalazs Yes, as you say interaction-free measurements look dumb to me. If you are not doing anything to the wave-function, then you believe in superdeterminism or other interpretations without superpositions.
@@samgragas8467 I think Sabine quite likes super determinism…
@@placer7412 If they’re unconscious, I don’t think you can say that they witness it. If witnessing it (consciously) collapsed the wave function (for want of a better description) I imagine that failing to witness it when unconscious would also collapse it *as long as the same information passed from the superposition to either the conscious or the unconscious person*. This is because even if the person was unconscious, the collapsed state could have been detected.
You do realize that checking where the particle *isn't* is *still interacting* with that particle, right? You are just interacting with it *indirectly* . So, no, there's really nothing weird about the same thing happening when you interact with a particle *directly* or *indirectly* . You are *still interacting* with it, in both cases.
It would actually be weird if *different* things happened in those two cases, because that would mean that the particle knew what you were doing, and chose (all by itself) to change its behavior based on that fact.
To me, quantum weirdness could look like an artifact of us living in a simulation.
Prodding the simulation rules are bound to yield some hard-to-explain insights.
People treat the math that estimates the range where a quantum particle CAN be as the particle being in all the places it can be and snapping into place when watched.
We don't change things by watching, unless we literally physically change them, we just don't know where they are unless we look.
Doesn't that show how incomplete established QM really is, ignoring these questions about the nature of an observer or a measurement. That's exactly what Sabine's research on superdeterminism is about.
@@Thomas-gk42 Oh for sure. It's just silly when the basic assumption behind the thing is so often taken out of context.
Your prisoner/guard comparison doesn't jive in two ways. you mentioned: a particle has no memory. But also, the prisoner doesn't escape by equal chance/time. He's more likely to escape early (He's gone--this is my chance) and later (He's been gone so long, it's worth my trying now.).
Agreed. Still a good example to get across the idea of how probability of an event goes down as you watch (since watching has an effect - can't escape while being watched) to zero once watching constantly. Not weird for the prisoner example but weird for a particle that isn't interacted with to have this same transition in likelihood the more you watch it or the more you watch the other state. We would intuit that a particle would have the same probability of escaping regardless.
Worst comment ever
that's not how analogies work
That you talk about "watching", while the paper cited writes "measurement-induced" puzzles me a lot. You can't see something without photons reaching your eyes, therefore you have to interact, right? It does not make that topic easier to digest for me when you say "watch" instead of "measure" - instead, it paints a wrong picture I'd say.
The experiment is shown as a set of cartoon eyes watching a picture of two lines.
That explains exactly nothing.
The previous shirt has dissolved into the background. The new shirt is the void where the previous shirt was...previously.
Thank goodness.
'That' is from your perspective, Mr. Observer@barrystock.Einstein.unv
From my perspective, Sabine is filtered without a shirt into my fantasy universe.
This literally sounds like a software program. That if you aren't actively utilizing a module it will kill its process, then when you go to look it reinitialize (with the random effect being described). No it doesn't make sense at all that when you look at something that it behaves differently than when you don't. That defies all reasoning of the physical universe. That does sound natural at all. That sounds artificial. Either we have this *really* wrong, or this points to a higher power.
Who could ever believe that blasting a sample in high-intensity radiation to perform a measurement could have an effect on the sample. How wild. These quantum guys sure are dealing with a head scratcher. 🤯
Didn't she clarify that observing the place where the particle is not makes the particle continue to not be there? That's a bit different.
@@adayah2933 well, i think this does not make a difference because you are looking at the probability cloud of the particle.
@@adayah2933One might be preventing the particle from moving there if the location is irradiated.
@@adayah2933 the place where the particle is not is a nanometer away from where it IS. If you are blasting one area with anything, then an area that close is also being blasted. It's the same area.
@@adayah2933 How does the particle know which particular place it isn't in that it's supposed to be in to not go there?
Very good description of gradient descent, watch the prisoner every 10 minutes until you are sure they are forever there
Warning:This video is not meant for "woo woo" minded. Watch it on your own risk if you are woo woo minded
Huh, "Woo woo minded." Like a train conductor, or...?
@@syntaxusdogmata3333 No, that's choo-choo minded.
Every particle is a little planet with little people on it who are watching through little telescopes to see if we are watching them (They can see our great big eyballs in the sky). This involves tiny little photons that are altogether indetectable except by tiny little people.
I'll show myself out the woo-door. 🚪🚶.
@@syntaxusdogmata3333 Woo woo minded is one step away from poo poo minded.
Arvin Ash seems to be using the term "quantum woo" to refer to made up magical effects based on misunderstood or misrepresented QM interpretations.
Now I have a _loose_ grip on the Zeno Effect. Thank you. New look! Good for you.
4:48 - The "g" in "tangential" is soft (as in "gentle").
Congrats upon the wardrobe-update, Dr. Hossenfelder :)
Something seemed off, then it hit home..
I watch my money in the bank, it is still there, or not?
It's a lot to owe but little to have. Yes and no?
I would say depends on your country 😂
Scrooge McDuck already knew that: You can only look at money if you can swim in it at the same time.
And swimming in paper puts you in a bad mood, it has to glitter.
I would add to an anology with a guard and a prisoner:
it's so happened that there's only one way outside of prison, so the guard may stand right outside, waiting for the prisoner to come out. But the prisoner just sits there inside the cell, even though from his perspective its the perfect time to try and escape. As if he has a 6th sense or accomplices or a way to sniff out the guard through the walls.
Disclaimer: I am not quantum or any physicist. Software developer who loves science.
My understanding is that the "probability" of changing states comes from our inaccurate observations. Let me elaborate:
It seems that human perception of time is sampled (or quantized?), we don't have the ability to truly observe something continuously. If we accept this then probability becomes something that we use to approximate the reality because of inability to make more precise observations. Say particle changes states every second, but scientists observe it with intervals of 2 seconds (because that is our limit for the purpose of demo). This will mean that our "continuous" observation will produce result which says that this particle is always in state 1.
By stopping "continuous" observation and starting a new one on the odd number we may or may not discover that particle changed state to 2, and thus calculate that particle has some elaborate probability of changing state, when in objective reality it always changes states, only much faster than we can perceive...
Well, the point is that not us nor our instruments are good enough (yet). In my opinion that is why probability is introduced in quantum mechanics, and maybe that is the best approximation we will ever have about how the world really works.
It may go a bit deeper in a physical sense. We have no reason to believe that the universe itself is capable of infinite accuracy. At physical resolutions approaching the planck scale we should expect to see real positional inaccuracy which we'd expect to show up as probabilistic outcomes.
As a fellow programmer, I find this theory very interesting!
@@Jesse_359 That's exactly what I am talking about. We also do not have a good reason to disbelieve it. All our knowledge based on observations (accurate as they may be) is used to build models which we use to subjectively reason about the workings of the objective universe. I really hope we continue to improve and will do better in the future
@@dimcha78 we have one real reason to expect that nature doesn't truck with infinities - they wreck probability. Positing a true physical infinity allows you to construct legitimate statements like 'everything happens everywhere at all times.' as a result of the irreducibility of infinities outside of the realm of mathematical abstraction.
For the prisoner example, when coming back and checking the 2nd time, the probability of him being there is still 75%. The 56% would require that you both did and didn’t check on him the first time; Did in order to reset his timer, didn’t in order to still have that first time give a 75% probability rather than a 100% one since you already know he didn’t escape.
I need to read more about the effect. I still do not get why some quantum objects have it while others do not. The ones I worked with (photons) do not have it. By the way, I studied physics apparently too early to have this in the curriculum.
@orangegummugger1871 No. I prefer odt 🙃
@orangegummugger1871 So you are serious? What kind of paper is this?
Somehow similar to Michael Ende‘s Scheinriese (Pseudo giant). You can watch him, but his size will always never change, no matter where he moves to. It‘s like observing the object from a movie’s perspective, but you can’t go out to observe it in reality. Of course, this example - like Schrödingers cat - does not really catch the point. For those who don’t know, it may look nice at the first glance, but it’s nothing but just another wrong track on the long path to understanding. The good news: Other than that cat, the pseudo giant can never be messed up with a quantum object.. (:-).
Netter Vergleich😊
Somehow a cat crept into my mind... 😎
Yeah, me too, I'm not sure where mine is.
I've seen the QZ effect explained _in seto_ in a very understandable way.
The wave function can change a little bit over time, but each time you look at it, it's reset to one of the observable states. So, it's more like a baseball player trying to steal a base then a prisoner!
The original reference is B. Misra and ECG Sudarshan
My apologies if these questions are dumb, Im still learning QM.
1) How fast is the collapse of the wave function? is it faster than C, can or has it been measure?
2) Can superposition and the subsequent collapse of the wave function be measured gravitationally?
3) Is it possible that retro-causality can cause the collapse of the wave function
4) is it observation or consciousness which causes the collapse of the wave function, have any experiments been conducted where an animal, such as a monkey to observe the outcome and react to the outcome ( a feedback system of rewards such as food etc given certain results, and conducted in a totally humane manner)
what about an AI bot observing the collapse?
5) How many times can a particle go to super position and collapse the wave function and does the particle lose any engird in doing so?
Something seems off about the Zeno effect. I’ll have to see how this experiment is being conducted and this conclusion arrived at.
The simple conclusion for me at this time would be that there is an interaction going on even when looking at where the particle “is not” thereby making any measurement dependent on the last.
I'll just post here my current understanding as some guy reading stuff but also curious on "observation"/"measurement": "Observation"/"measurement" is us "putting" some material "we can move and touch" in the setup so that when the particle/wave (we think) goes there, some indication (maybe something like a dot or a change in electric current reading I guess, etc.) appears and *we* can detect it. The "we can move and touch" is important here: interaction between individual particles (when we calculate in theory) are not considered as measurements.
The double slit demonstrates the wackiness: single electrons 1) put dots in measuring plate, 2) put dots "everywhere" for some reason, but 3) after many electrons, the dots form that well-known interference pattern. Now the smarts among us developed the concept of wave function to explain 3), but the reasons of 1) and 2) are debated; the "why" of 1) is the "measurement problem" (if wave function of a single particle is physical, why it forms dot in the plate?).
So this explains why when I blink for a second during math class, my teacher had already filled the board with equations
Ah I always knew that guy was in a superposition
Sounds like you've got trucker eyes. Some of those guys blink for about 20 miles at a time.
I have the feeling that the example of radio-active decay is a bit misleading, in particular contrasting it with the transitions in a two-level system from the start of the video. In principle, there is not much of a conceptual difference between decay in a two-level system (e.g. an electronic excited state and the ground state in an atom), and radioactive decay.
In the former case, the transition between the states is mediated by the electromagnetic interaction, and since the final state has vastly more phase space with an emitted photon in place, the time arrow follows from the entropy argument in the absence of thermal equilibrium with the electromagnetic field surrounding the atom, which is usually the case on earth with optical transitions of atoms.
In the latter case, the transition between the states is mediated by for example the weak nuclear force.
The only difference is that in the electromagnetic case, through the use of tunable lasers (providing high fluxes of the mediator of the electromagnetic interaction), we have powerful tools at our disposal to engineer the quantum measurement on the atom in a highly controllable manner.
In the case of the decaying nucleus, we just can't probe the initial (or final) state of the nucleus directly in a comparable way as with the atom, but that's only for technical reasons, not for fundamental reasons (unless I misunderstand something about QED and QFT in general, which is totally possible).
Then, secondly, the memorylessness and the fact that a vast ensemble of radio-active nuclei can be modelled with a Poisson process, resulting in a Poisson distribution of total counts during a finite time interval which importantly needs to be much shorter than the lifetime, has more to do with the size of the ensemble and the statistical independence of the emitters than with quantum measurement. As a matter of fact, a large ensemble of independent decaying two-level systems (from the start of the video) would show the exact same phenomenon (if you put a single-photon detector nearby, instead of directly probing the evolving quantum system(s) with an external light field)!
Wave function and its collapse should be the most studied subject in physics. It is such a fundamental phenomenon that we can only describe but we have no clue what it is...
No it shouldn't. "Wave function collapse" is an entirely classical phenomenon and entirely misses what makes quantum mechanics unique. People try to make it mysterious by calling it "wave function collapse" which gives you a mental image of a physical wave that is collapsing like a house of cards when perturbed. Yet, there is no reason at all to believe such a thing. The wave function is just a function for choosing a probability amplitude from a list of probability amplitudes, and this list is called the state vector. The state vector contains the likelihood of each event occurring. You update this vector when you acquire more information, and the update allows for it to be simplified ("reduced") because many of the amplitudes will be updated to zero. It is more accurately called the reduction of the state vector, which is also a feature in classical probability theory as you also update your probability distribution based on new observations which can allow for its simplification.
This doesn't even have anything to do with quantum mechanics and the insistence that it is "mysterious" is based on a bunch of assumptions which are simply never justified, particularly that the state vector does not actually represent a list of probability amplitudes but instead the dimensions of a physical wave in an infinitely dimensional space that undergoes a physical collapse like a house of cards when perturbed. There is just no reason at all to believe that, nothing in the theory requires you to believe that. The infinitely dimensional nature of Hilbert space is again just something carried over from classical probability theory: the more events you are including in your model, the possible configuration of events grows exponentially, and so you need exponentially more probability amplitudes. A state vector for a single coin needs two probability amplitudes for the two possible outcomes, but for four coins it would need sixteen probability amplitudes for the sixteen possible outcomes. This is why the number of dimensions is unbounded and it has nothing to do with there literally physically existing an infinitely dimensional space whereby infinitely dimensional waves fluctuate.
We know with certainty what the so-called "wave function collapse" is, it is nothing more than updating your prediction based on new information acquired, which is something you also do in classical statistical mechanics and is not even inherently "quantum" in nature. The people who insist it is mysterious make tons of entirely unjustified assumptions about what the wave function actually represents which they have no basis for other than wanting quantum mechanics to seem more mysterious than it actually is. Indeed, quantum mechanics differs drastically from classical mechanics, but not in the reduction of the state vector. Where it differs lies in the fact that probability amplitudes can be complex-valued which gives rise to interference effects, something which there is no analogue to in classical statistical mechanics.
So where do we begin? According to me, there’s more than one way to travel faster than light. One way is associated with wavelike behaviour, the other with particle-like behaviour. No need to be in any hurry to agree with me, but the answer is likely to be just as weird.
"Particles don't have a memory" I'm not sure about that. I have known particles who not only had a memory but would also hold a grudge.
Particles are untrustworthy rat bastards...
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If you are looking at where it isn't you are sending some energy to the spot where it isn't. If it was about to change to the other state it could almost get there then get the energy from the place it wasn't and switch back. Seems natural it would be at rest more where there is less energy. Hence, where you are not looking. An interesting experiment would be to have two places being looked at with different intensities of energy. Will it be in the place where there is less energy a larger percent of the time?
Sabine I have a question, maybe it can be a future podcast subject. While human consciousness seems to somehow effect a quantum state, has there ever been an experiment using non-human subjects like a dog, cat, or some other animal to see if their presence and gaze has the same effect?
How do you want to verify that? To verify it, you have to observe the whole quantum system including the dog, and so a huma being again is part of the observation. It's exactly what the "Wigner's friend" - though experiments are about.
Better illustrated using quantum tunnelling where the two states are symmetric energetically. You can then talk about normal modes and how observing any part of the well causes a "disturbance".
If you leave anything that can explore options with only 1 option, then sooner or later the one option is taken. By occupying the same Optional-Space via constant observation, the option is gone.
So the zeno effect is just a hint, that quantum systems are in fact exploring possible options.
The decay case is different in the sense that your observing the atoms surface and there are plenty of options for the decay to happen.
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Hmmm why does a 2-state system exhibit "memory" while a radioisotope doesn't?
What about decay of electronic energy levels, like in a molecule?