#5minphysics
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- เผยแพร่เมื่อ 23 เม.ย. 2020
- Quantum Entanglement is one of the weirdest, and currently perhaps the most technologically exciting aspect of Quantum Mechanics. But even though the measured state of one object instantaneously affects the state of another located across the galaxy, this doesn't allow faster than light communication, alas, as I show in this #5minphysics episode.
Simple but one of the most effective explanations of quantum entanglement I have heard - thank you.
The second half feels stupid. What stops us from locking one particle in one state to see the other getting locked? What makes particles "look" entagled if they don't behave differently from unentangled as you (Lawrence) say?
So honestly what needs to be developed is the ability to constantly monitor the Quantum state, and the ability to force the "Switch" of the state to the "Direction" that you want, we don't communicate via CB radio by just watching the random radio waves in nature but by harnessing the power and generating the waves so the match the shape and form we want. we can start with the current on off design 1's and 0's of modern computers or evolve to develop quantum state computing introducing multiple dimensions. For read write capabilities.
Thank you for the free lecture professor. ☺
I was first exposed in a serious context to the notion of entanglement in a quantum computing class. We explained entanglement by saying that you can't write an entangled state as a tensor product of pure states, which of course made sense but was rather limited, so I'm really pleased to see an explanation this good and this physical. The question of "what actually happens physically" is not well liked by computer scientists :)
Question though- If two qubits are in a maximally entangled state, applying a gate to one will effect the state of the other. Currently the channel has exactly a 50% chance to flip- Why couldn't we work out a code to set up our qubits in such a state where that level of noise will be lower, and then use an error correcting code to deal with the remaining noise? I think I'm missing something but I'm not sure what. Thank you for the video!
In the time it takes to imagine a nanosecond a billion of them have expired.
Ok I asked a question about this in the past, but I've refined my example. Consider the following:
I have 2 space stations, A and B - they are 10 light-years apart. A pair of particles has been entangled and are each stored at a space station. I want A to be able to send an instant message to B. I decide in advance of positioning the particles:
1) Station A will observe it's particle (lets say it has an up-spin) and keep that particle under uninterrupted observance.
2) Station B will observe its particle (it will of course be a down-spin due to the entanglement). Station B periodically observes its particle (lets say, every minute) - this will always sown a down-spin as the observation of particle A has not been interrupted.
3) Station A is under attack - to single station B, they STOP observing their particle.
4) Station B continues to observe their particle every minute - as the other particle isn't being observed, the particle at station B could be either up or down (not just locked-in to be down). So eventually, after a few minutes of regular checks, station B records its first ever up-spin. This is the agreed upon signal for "we are under attack".
In my example, information has undoubtable been sent instantaneously (all be it very simple information, but surely an alert counts?) Were any of my premises or assumptions incorrect?
I feel if I get an answer to why my example can't work, I will finally understand this FTL communication issue.
Nice. So if I understand correctly you've set the communicator up for a later date which will then make the message instantaneous?
I think the solution to your problem is that you are assuming entanglement persists even after measurement, which I don't believe is correct. Once you measure a state, you collapse the wave functions and the entanglement is gone. So yes you can keep observing the particle after the initial wave function collapse, and it may change state, but its nothing to do with the other particle after that point.
simply enjoyable!
Thank you!
Wow! That really is all those things you mentioned, strange, spooky and crazy! Even though had to view this video several times, I still really haven't got my head around this and have a million questions to ask but ah!, that's ok, I was still absolutely enthralled in watching this. So thanks again Lawrence and you have a great weekend too. And btw, you should think yourself lucky you have hair to cut ;-)
i also have hair on my genital part to cut, in the head unfortunetley i have no hair, i must implement some quantum teory to make possible for my hair to grow :))
This is probably impossible, but I have not seen this suggestion in the comments below, so please someone debunk me :D - I set up 3 stations. One in the middle of the galaxy, sending out entagled particles, one partner left, one partner right. On the left side of the galaxy, I measure all electrons I receive, colapsing their wave function. On the right side of the galaxy, they have a double slit experiment set up and since these electrons are already collapsed (due to my measuring in the the left station) they get the "particle pattern". Therefore, if the left station stops measuring, the right station starts receiving an "interference pattern" instead. Alternation between particle and interference patterns creates my 0s and 1s. ...
Now, I assume that entangled particles will never produce an interference pattern or something like that? :/
Good point...I wish someone would respond as to why that wouldn't work. I also thought you could influence the particle pairsso as to show left-right vs up-down spin (by measuring at an angle), so that feels like you could encode something by horizontal vs vertical. I totally accept that there must be something wrong in my assumptions, but I wish someone could explain what it is.
Would you have to sync the stream of entangled particles being measured because of the distance difference? The station would have to be able to move exactly half way between both partners or else the earlier particles are discarded?
You are correct. Entangled particles will not produce an interference pattern. Both particles would need to go through the slits and they can't because they are on opposite sides of the galaxy.
The interference pattern is what we want due to a logarithm received from the other particle.
That's exactly what I concluded in my efforts to make it work, by using particle observation in a true/false manner as a means to code a message. Measuring particles in a predetermined and well timed sequence could act as a Morse code so that the position of the particle is irrelevant, only the fact that a particle was observed or not. I totally believe that it is indeed possible if both parties were equipped with sufficient entangled particles but that's where my understanding breaks down. How are entangled particles stored? How many particles pairs can there be in a system?
Thank you for yet another fascinating mini lecture. By the way, I love the title "Five Minute Physics". The fact that you can get some of these concepts even close to five minutes, and have people understand them, is downright amazing! I realize that you are just giving us the very basic concepts, and that there is much more to what you are teaching us. Now it is up to us to go out and learn more! Thanks again. I look forward to more next week. PS. I would really love to understand how a black hole can evaporate, and what happens when black holes merge...what is actually merging??
Black hole "evaporation" is a deep subject. It's known as Hawking radiation. Lots of videos about it. BUT trust me the answer is long and very disappointing. In a nutshell it takes trillions of years for a Black Hole to evaporate. So for all intents and purposes other than Hawking wanting to prove a point, Black Hole (Hawking) radiation doesn't affect anything.
Thank you Lawrence ❤
This finally made sense! Thank you
Best explanation of entanglement I've ever heard. I have been trying for a decade to get my head around this, and now I understand it in a way I can explain to others. Thank you! I will use this to teach my kids about entanglement.
Thank you and enjoy the weekend!
Quantum entanglement explained in a very simple way. Thanks.
Thank you for the explanation sir!
Thank you so much, I love your explanation. I'm not even in collage yet and I was able to calculate mass of the sun. I'm so happy😀
This was a ridiculously convoluted way to describe quantum entanglement.
I think that Physicists try very hard to explain away the possibility of breaking general relativity. But how would they react if someone actually invents a device capable Faster than Light Communication? using quantum entanglement in creating ways? For example continuous reading of up and down spin on both particles, and translating to morse code. If you can continuously measure both particles, and force a spin state to a particle, then ftl communication is possible. The particles would need to maintain a state for a period of time, then the instrument would need to force a change of spin on schedule. This could in fact look like a morse code signal. The key is to make the spin detection on the other end look non-random.
Looking sharp with your hair cut Lawrence!
My understanding of quantum entanglement is that it is a channel where you transmit only random things. You cannot decide what you send. Therefore you cannot communicate what you want.
I get that we can't use the actual state to convey information across distance instantly, but since it's time that this arrangement kind of sits in, why not perturb that ? For example, set up an array of quantum states, (qbits ?), and agree here and now that the time between the changing of a particular qbit in the array and another particle in the array has a meaning. Holding the array in place is the tricky part I suspect... If I change the particle positioned at 2,5,7, then 0.0001 seconds later the particle positioned at 4,5,8 this means "x" whatever this is, could be anything. But if it happens 0.0002 seconds later this means "y". So it is the time between the act of forcing the change that is the information. Thanks so much for the lectures and interacting with your fans.
I know it seems frustrating.. but all the observers get to do is measure one part of the entangle state.. they don't control it or set it up.
Sorry if this was asked... I didn't have time to read all the comments. So... what you drew on the paper is literally binary code. So... if instead of 1 "pair" of entangled particles, use lots. So you take box A (call it transmitter) and fill it will lots of entangled particles that will get observed in a pattern. For instance particle 1 gets set to 1and particle 2 gets set to 0, and particle 3 gets set to 0 and particle 4 gets set to 1. The other half of these entangled particles are are in box B (call it receiver). Now it is going to "display" a reverse of the pattern that was transmitted. Since it knows that it is reversed, it will take the 0's and 1's and flip them to make it easier. So it takes its "string" of 0110 and makes it 1001. That is 9 in binary. The more entangled particle you have the more data can be passed at any one time. Send 256 entangled particles in two boxes and take the transmitter with you on your voyage to Alpha Centauri, and report back using 256 bits of information at a time... in binary, or Hex, or ASCII, or EBCDIC (like in The Martian), or whatever you want. Why can't that be done? You would even add enough extra entangled particles to act as error checking (checksum) characters to the message to be sure it is a coherent string of characters. Just like old modems used to do (and to some degree still do across the Internet to make sure the data that arrive is not corrupted and such).
Laurence this is the simple example of a single two state simple entanglement. Most people now get that. The question though is with entanglement of say orbital angular momentum with many many particles and then not looking for a specific state but the “effect” of interfering (1) or not interfering (0) with the set of entangled photons.
Love this 💙😍
hello sir, please explain, how asymptotic freedom of quarks work?
I always watch your videos
That great, really great!
But I have a question, (hope that it's not a stupid question)...
We can't control the Direction of practical's spine in any way????
Can you use quantum entanglement to safely share a symmetric cryptography key (just key) between two parties without the capability of man-in-the-middle attack?
Hi Professor Krauss. You are such an awesome explainer. Can you please explain the concept of spin in a future #5minphysics video? Thank you for these simple but insightful lectures.
GREAT IDEA!
Yep, I want to hear about spin too. And it's not as simple as how we ordinarily define spin. In fact its explanation seems to be avoided.
I want to hear about spin too
Instead of insincere fault finding what is and is not experiment, I prefer to sincerely ask, "What is and is not INTERACTION considered to be during that experiment?"
Understanding what preserving their state is and is not should help this make sense to me.
It seems like the first thought of all software/networking-knowledgeable people is to say "who cares about the spin values? if you can check whether a particle is still in a superposition, then that's good enough to communicate a 1 or 0 and then you can string the particle pairs together into a suitable message. i saw elsewhere in one of the rare videos that mention it that the problem with this idea is that you can't TEST whether a particle is still in a superposition without being next to its partner which defeats the purpose of communicating at a distance.
So hypothetically, if one had the technology to try to control the outcome of a particle measurement, would it be correct to say that this interferes with the entanglement of the two particles?
Where the entanglement breaks down when one obviously has an external force placed upon it to force one state or another while it cannot be known that the same force is or is not applied to the other particle lightyears away?
Why do you need to know whether it's a 1 or 0? Can't you just communicate with morse code, meaning who cares of it's a 1 or a 0, as long as you're seeing something, you can count it as a 'pulse'. The number of times you see a 1 or 0 is the number of pulses. Then it's morse code.
Sounds like an interesting idea, obviously this can't be measured as a measurement on either side will collapse the state to either 0 or 1.
What you would then need on one side is some sort of device that ticks whenever an electron gets in a definate state(instead of a superposition). But wouldn't that device itself be measuring the particle, thereby causing the collapse to a definate state itself?
@@dekippiesip how are they measuring the result in the first place? How come the result is not affected with their measuring device? So just replace the measuring device with a ticker. And if you get the ticker to work, all you have to do is tick at the frequency of sound waves and now you have full verbal communication.
I had seen you in TV channels when I was a child, 9 y/o
Now I'm 15 and happy to find you
Good one
None of these are 5 minutes :) I still love them
can you change the spin and therefore flip the spin on the other side?
Professor Krauss really fascinating video thank you. Interestingly, I discovered you and your work recently while working of a research paper for one my university classes. I have watched a lot of your lectures and I would love to ask you some questions I had particularly from your lectures titled "A Universe From Nothing". If this is possible it would be a privilege to talk to you. I am not sure if you read these comments, but regardless thank you again for the video!
Thanks.. good luck in your classes.. I get tons of requests with questions, but you can always try and email.. I try to reply, however briefly.
No matter who I listen to explain this, all I hear is that these particles are IN SYNC and not affecting each other whatsoever.
In simple words, unless we learn how to control the spin so we can force it to be a 0 or a 1, we cannot use it for communications at all because the measurement of the spin is random (you can get a 0 or a 1 randomly and that doesn't help, we have to force it to a 0 or a 1 so it becomes actual information). If manipulating the spin is possible somehow, and we discover hot to do it, and we verify that after the manipulation the entanglement continues (so we force a 0 on one side, the other becomes 1 for sure), then we are in business. Still it will require to send the particles somehow to the other point we intend to communicate. It would be useful at short distances like within our solar system, for example, a colony on Mars, or a moon in Jupiter or Saturn. Would be also useful for space travel in general, if one day we are able to reach real high speeds and we send ships to another solar system, it would be perfect to maintain real time communication with the ship.
How would it work? well, if we can manipulate the spin and for the particles to give a 0 or a 1 at will, then, we would need to keep measuring the particles ALL THE TIME. then you can set one particle as the "ring tone", meaning, when I want to make a call, I change the spin. the other side will detect the change and the "phone will ring". And as so, the next set of particles will provide different signals like starting the connection to receive 0 and 1 that will be used the same way we use them in computers to create text messages, audio and even video communication in real time. But again, the key is to be able to control the spin. otherwise, is just a bunch of 0 and 1 without logic, they are random.
Maybe sometime in the future it will happen. But I doubt the current generations will see it.
When you say instantaneously... is that based on whose local time? Who chooses the time of read-out of the second value? Do we even get a choice? eg if particle 1 is spin UP at 12:00am does the theory say I can read out particle 2 at 12:05am and get spin DOWN? Or does the distant particle "respond" only during the first wave collapse measurement? How long can I muck about before the second entangled particle is read out? It seems to me whether the time limit is zero (instant), or near-instant (say a femtosecond or light-millimeter) it must still be faster than light information transfer. If it is the same or longer than the time taken for light to move the gap... then it would hardly been strange or spooky: the hidden filament that links need not exist physically, it could actually just be a side effect of both particles having synchronised internal clocks that keep sync no matter the distance. The ticking clock maybe captured by their phase angle say. Like two actors reading from a script but slowly walking away from each other, they keep perfect continuity, each turning the pages of their scripts, swapping characters with each page turn, yet never experiencing a double-booking nor speaking at the same time.
You would only have faster than light communication if you could force one of the entangled pair into a certain orientation without breaking cohesion. Its partner, when measured, would have the opposite orientation. Theoretically if you had enough entangled pairs, and the receiver knew to check their particles, you could have faster than light analog communication. There's a Nobel prize for discovering FTL communication waiting for you if you can figure out how to convince an entangled photon to spin in a specific direction.
Yes I was thinking the same, if you have 26 entangled particles, all I'm different boxes each box correspondence to ever letter in the alphabet.
When observing A it would show in the other particle you were observing at you could string together a sentence from which ever you observed.
I know it can't be that easy they would have thought of that so I wonder why it is you can't send information faster than the speed of light.
Longer is Better , Please keep going , thanks.
What if we could find a way to force the outcome without messing up the entanglement?
they will one day
I've thought hard of it but
When you force one of them with the entanglement preserved when will the machine 1000000 light years away know when to measure ? so defeats the purpose
@@spec_wasted Both machines could have a set time interval (1min, 1hr, etc) where one machine forces the outcome of the particle while the other one observes. Maybe a specific particle outcome could signal to the observing machine that its now their turn to "send" while the first machine switches to "receiving mode". Just an interesting idea I had but idk if it would work
I actually understood your explanation! My only question I've been wondering is once you observe a particle, will it become disentangled or will it stay entangled? Or is there a way to re-entangle the particles at a distance?
The answer is yes! Another reason I don't buy the no FTL communication argument.
@@jok2000 so you can re-entangle at a distance?
@@ryanellis120 No but I currently suspect that you can use 3 entangled photons and then do the Bell Experiment/ measurement on 2 of them. "Quantum Flytrap" doesn't seem to be able to do the Bell Inequality, however, so no data yet for me on what the 3 photons communicate in the experiment if you measure one.
Please someone answer , can we force one of the photon to take upspin everytime we measure ?
Anyone
Sir,
Just curious, may be a silly idea. You explained that particle freezes its state when it is observed.
So we have 2 states here. particle is either active or not active. If we consider active = 0 and not-active = 1
and if we can use a device (like a camera) to observe and stop observing we create a pattern of 0s and 1s.
So if we have 2 particles connected and at one end we can create 0s and 1s by observing and not observing and the other end if there is a device to capture state of the particle whether it is active or not,
it can find the pattern of 1s or 0s. Do you thing there is a possibility of making such a communication method.
Love your videos. They are super "hyggelige" as we say in Denmark.
Ja det er rigtigt ❤👍😁
What if when I want to communicate up to you I just keep measuring it until I see down here, then I stop measuring? So, if you see "down, down up", you know the message is "up".
Simple and effective.. thank you
I'm not a physicist. So I'm struggling to see what all the hype is about? To over simplify it. It feels like a RSA token. Once the code is set. The numbers look random but they are predictable because of the original predictable source.
My uneducated question is, can you change/influence the spin once they are separated. Does that influence the other spin? That to me would be "spooky", though that's not what im hearing.
Idk, as of yet no
Yes you can influence the spin after a period of time. Measure it later.
I thought you can control whether the particle spins up/down, left/right.
Can't you make it so that
spin up/down=1, left/right=0?
Nicely done. I'd like to see your explanation of how an entangled quantum state is prepared, from the beginning. At the start, I turn on the laser that illuminates my BBO crystal, then a few microseconds later Alice and Bob start recording the times of events in their APDs, a kilometer away, say. My question, which I ask in Section 7.2 of a paper in Annals of Physics last month, "An algebraic approach to Koopman classical mechanics" (arxiv.org/abs/1901.00526, DOI there), is whether the entanglement starts *exactly* as quickly as events start, or whether entanglement is established slightly or much more slowly than that? I don't think there are any experiments that establish this, yet, but it's important to know for technological purposes as well as for foundational purposes, because sometimes the power has to be off.
Gregor Weihs suggested to me that pulsed source implementations of Bell violating experiments address this, but such sources do not give access to the relative timing of when entanglement starts. I also have a longer discussion, but I'm expecting you and others either not to notice or not to respond to this comment, so I'll only elaborate on request. Also TH-cam comments are a close approximation to the worst way to communicate.
i may sound silly, but will like to put this thought here. If all computers and satellite communicate through 0 and 1 , can once set on the quantum entangled particle readers on far gone satellite be reading the data from its observation like Voyager , and converting the same to 0 and 1 ( of quantum entangled particles) , then the other set on earth will decode the same data based on the quantum state of 2nd set.
So one is up and one is down but the only way to be sure is making a slower than light phone call to confirm? But if they are entangled won't you already know?
Can i prepare a entangled state of three particles. lets say i measure first and last particle very accurately at the same time(thought experiment) and the one came out as up and the other as down. What happens to the middle particle?
it depends on the state you prepared them all in to begin with
My question is. Being it that the quantum entanglement is holding two particles and they produce a binary response on detection. Is there any way to manipulate the spin state for example. Planet A has the ability to flip the rotation of the electron at will. Let's say as a static test they keep it pointed up. But if they manipulate the electron into a down spin and then an up spin.. would this not allow for Morse code style communication? Or am I missing something fundamental?
From what i can guess, forcibly manipulating a particle to 1 particular set of states changes what the particle is entangled with to the thing applying influence to it.
Sorry for stupid questions (I never went to a university). But is this what happens in the two slit experiment? One particle splits up entangled as long as we don't know which slit it went through and interfers with itself to create an interference pattern? And don't when we collapse it by measuring it befor it has the opportunity to do so?
well a particle interfering with itself is not technically entanglement, but I guess you could say that it is the single particle version. :) (note that a single particle is always correlated with its own wave function)
@@lkrauss1 my thinking was that one particle got split in two. Like the cat. We don't know if it took the left or right slit so both happens and only collaps when measured. It sounds to my like the same as when your hands moved apart with one top and one down spin. Then the two interfers each other untill the detector wall collapse it.
@@Syncroniq I know... but it doesn't really get split into to.. it is just in both places at once.. but you can think of it as a kind of entanglement, in that the wave function is spread out over space.
I am having trouble visualizing the "pointing in all directions" just as I do with visualizing the electron "cloud" around atomic nuclei.
Are the two difficulties related?
I can freeze the image in imagination so that it 'points' in one direction while I ponder.
Is that a legitimate maneuver from a physics perspective?
I mean, couldn't there be something in the freezing that can't help but tell a lie?
In digital processors the CPU accesses all RAM locations in the same amount of time.
If we are in the Matrix, where the speed of light is what it is because of the particular algorithm that manages it, could entanglement be considered evidence to support the contention that our existence is virtual? (what with the fact that access to any particular instantiated particle would take exactly the same amount of time as access to its entangled twin)?
Yes the two difficulties are related because quantum systems can be in multiple states at once. Thinking of a ball spinning clockwise and counterclockwise at the same time is difficult because classically you can only have 1 spin state. We are used to some objects having multiple states classically though, like colors. What if blue was clockwise and red was counterclockwise, then both would be purple.
Space and time exist because there is a speed limit to causality; if there wasn't, nothing could be causally disconnected. The speed of causality allieviates the interdependencies by disconnecting them, and makes it possible to actually calculate a complete state. This is the best argument I know of that we are a simulation.
What if, before i fly to alpha centauri i tell earthlings that: "if you measure 3 up spins in a row that means i wanted to say yes" and "3 spins down in a row means no". Would i be able to cut in half time needed to recive an answer to a yes/no question by being able to answer instantly? Since time will be needed to send question, but no time will be needed to send "yes/no".
When answering i don't need to have any control over spins, just measure them enough times to get 3 "ups" or 3 "downs" in a row which will tell the answer.
need answer to this
I think once you measure a particle, the wave function collapses and the entanglement is over. If so, the only way to end your sequence at a certain desired state (e.g. 000) would be measure many entangled particles and stop once you hit three 0's. But the other observer won't know how many particles they have to look at to reach this point, you would have to communicate that information via conventional methods.
Good example, but I still have an example:
- Me and my friend are 10 lightyears away
- We are using a system that can exist in 2 states (off and on)
- We want to ensure our systems never exist the same state (and we record all states in a central computer)
- We have a quantum entangled pair, 1 particle each, and set the system state (on or off) to correspond to up/down spin of the particle
- We agree beforehand to measure our own particle and readjust the state of our system to on or off periodically
In doing do, we guarantee our intent (each system was never in the same state at the same point in time) using only the entangled particles as a way to determine state (if we got together we would see that our past data shows that systems were always in a different state, as desired).
Instead of calling my friend to decide upon system states (via a method with sub-light speed) we have done instantly using the entabgled pair (in-spite of the 10 lightyear distance). Is this NOT a form of communication? If not, WHY not?
What are you communicating? There is no communication here. There is no transfer of information is there? Also once you measure the particle it will keep that state.
@@stinkiaapje Can't you just move the particle to a different state so that there would be communication?
Is there any way to know if the other particle was measured? Probably not but still asking.
That is the real crux of the problem. Not if the spin can determine 1s and 0s (it cant, its random), but if the collapsed/not collapsed state can produce 1s and 0s. I also asume it cant, but dont know why yet. I guess that a stream of entangled particles will never produce wawelike interference in the double slit for some math reason...
Hi Mr. Krauss. I really enjoy your videos and you do great works. In this video you give an example of describing correlation, however, Bell's Inequalities seem to indicate that there's more going on than just correlations. Remember, if you're using "coincidence counters" in your experiment than you are measuring coincidence (aka correlations). The circular reasoning seems apparent when phrased like this: "We can only prove a particle is entangled with another particle if we can compare it to the entangled particle".
I speculate FTL communication, if possible, would work something like this:
binary 1 = particle is entangled
binary 0 = particle is no longer entangled
For some stream of particles the measurement would be compared against background noise, not to its correlated particle(s). This does not seem to violate having anything travelling faster than the speed of light, however, it might be time we investigate our understanding of causality at the quantum level.
If A and B know that they were prepared in an entangled state and if they decide the times when A is going to measure his qubit before A moves light-years away from B, then doesn't that already imply that B would know the state of A once he measures his qubit after the time of A's measurement
Maybe I missed it in the video but did you talk about inducing spin on one of the particles? would that destroy the entanglement or something?
what I said, I think, was assume the two spins had been prepared together in a total spin = 0 state initially.
@@lkrauss1 If there is no further manipulation, merely a measurement which gives a random result (due to superposition) then why even bother throwing the dice in your demo? The fact that you are using a dice at all shows there is no data to communicate. A random binary number generator is all we have and it is irrelevant whether it is inverted or not. If I understand correctly that is.
That certain someone did a very nice job on the haircut. :)
I had this idea about it and please someone tell me why this doesn't work?? I ask in various places and nobody has replied. I am sure someone smart thought of this and knows why it doesn't work, I just want to know why so I can learn more about how it does work.
My idea is this. If you define a fixed time period based on a pulsar conveniently placed halfway between you and the recipient of a message. Both sides can measure the pulsar and we assume its stable over time.
For a one-way communication example: Side A wants to send a message to Side B. Each period (cycle of the pulsar) Side B then measures the spin and resets it to the base position known only to side B (no communication needed to side A from side B).
If on the next measurement cycle, the spin has changed, that means side A wants to send a 1 and if side B measures the same spin again, then the message was a 0.
You can error correct in the case that side B base position was the same as the "send a 1" position. Since there is no reliance on the actual direction to signify any information you can have multiple entangled pairs pointing in various directions as error correction. The important information is "changed from last measurement" or "unchanged from last measurement"?
I am sure I must be missing something here.
When observer B sees a 0, he instantaneously knows A has 1 due to quantum entanglement. Information transfer seems to be faster than the speed of light, since it would be instantaneous. There doesn't appear to be the need for a telephone call to convey such information. What have I missed?
What if the state of one particle wasn’t a dice roll? What if it was in a controlled environment, like a magnetic field that we could use to make the particle either spin up or spin down?
Macroscopic entanglement was what I was curious about, Nature just announced that there is such a thing; good old synchronicity.
Could there not be some sort of deciphering protocol to initiate conversation? Say we measure at the same frequency, but only one side can ‘speak’ at a time. And one would know that a piece of info is a message based on the low probability of designated chained 1s or 0s
So basically, there should be a direct connection to see if the particle’s state are indeed entangle. And, because of that, we still have to use physics that can’t achieve faster than the speed of light. It might be a stupid question but what if we apply the blockchain structure? In order to change the state of the data, you have to be a part of the block.
So the reason we can't use quantum entanglement for communication is if we try to manipulate one of the entangled particles it breaks the quantum coherence?
Professor Krauss...I thought I knew something about Quantum Entanglement...Now I realize I did not. Thanks for your education.
My understanding is that you can't alter one particle's spin between spin up and spin down, causing the other particle to flip between spin up and spin down because once you make a measurement, the entanglement is broken. If you could, you could sent Morse Code messages, but you can't. Is that correct?
after you have made the measurement,, if you act on the first particle then entanglement is generally broken.
Can't she use an aligned magnetic field to force an 'up' spin - this makes the other side 'down' ?
Or does an aligned magnetic field simply force 'up OR down'
This immediately raises the question: can't you put one particle of the entangled pair into a specific state, thereby instantly affecting the other particle. In other words, can you control the spin while maintaining the entanglement? I know the answer to this, but I'm fuzzy as to the why.
whenever you measure the first particle you put it in a specific state, and do not affect entanglement.
@@lkrauss1 So then, why can't you do this again, thereby allowing communication? Or is it simply random every time?
@@mikeg8028 every time
@@lkrauss1 Thanks!
This answers my question too
I don't think it matters if you tell the second observer it's entangled. Since the very fact it's part of a communication machine makes that obvious. One question i can never find an answer to. Can we artificially induce a certain spin thereby changing the state of the second particle. Also how long can you keep them entangled. If you can control the spin then up spin is 1 and down spin is 0.
whoa,
Lawrence Krauss! i didn't know you had a youtube.
it's so weird to see a top thinker like you interacting with the new age flat earthers in the youtube comments. lol!
but i guess you're used to people like that, i've seen you debate religious people a lot
Hey, don't forget about the Creationists.
Can't observer B have some sort of prior agreement with A, such that what he observes, s/he just takes the message as is?
So, when A makes a series of measurements at pt.A, particles at pt.B would have their states affected. B simply measures them and `trust` "oh A made measurements" and take the message as is without requiring a call from A?
My thoughts as well something as simple as a computer program constantly measuring observations in 1 second (arbitrary time), measurements and resetting every 100 (once again arbitrary variable here) “downs”.
Both sides know this prior agreement, so assumption is every reset a message could be made. If up is 1, and down is 0 binary could be understood right?
So for example, team earth, and team alpha centuri. Both have a prior understanding that earth’s entangled particle is up (1) and alpha centuri’s particle is by then down (0) because this was understood before alpha centuri left. Alpha centuri is now at their destination. The particle hasn’t displayed anything different than down the entire duration of travel. Now the computer reads up (1). Is that simple change not communication? And with this prior agreement could an established line of communication not be established and maintained?
All of this is assuming a constant can be established. And assuming both sides can control that constant.
there is no information in a random sequence
@@lkrauss1 Arh, so the measurements by A would yield a random sequence of values? In a sense, it will not be able to send a message by itsef.
So the message(that is within the speed of light) from A to B, if using this method is one that contains details on how A encodes some message from the list of measurements(e.g A, can say "omit so and so measurements' values" so that the remaining measurements will be able to form codewords) which therefore puts a limit on the speed of transmission?
@@lkrauss1 But is there a way of telling the difference between a colapsed "particle" and a wavefunction? In the double slit experiment, if they are measured during the test, they provide a particle pattern. But if not, they provide an interference pattern. That would suggest, you can tell whether measurement was made before or not, just by looking at the patern in your double slit experiment?
Can you please re-order your playlist so that it plays all videos in the order you released them? Right now it plays them from last to first. Thanks.
I always thought last to first was better, but I guess I can do that.
done
@@lkrauss1 Thanks! When you talk break up the same topic into several videos it can get confusing. :)
@@lkrauss1 Also if last to first is the order in which you intend us to watch them then it's fine obviously. :)
On Alpha Centauri, a person writes down their result, and the light speed confirmation comes much later, but the written record doesn't change.
So why can't we control the spin direction of one particle? Example for particle A into down knowing that particle B would be down. It just seems logical
I've been wondering if you could use the entangled state as a simple signal. ex 'Hey what we previously agreed on has happened'.
Unfortunately no. Because Alice can't know when Bob measured his particle. Alice can't know what spin Bob measured. So, no. I was really hoping decades ago that someone would find a way for FTL communication but what they found is, FTL with entanglement is not possible.
@@stonkwhisperer5590 what about Alice and Bob agreeing to both look at the particle at a set time. Then depending on the state, Bob is supposed to either do action A, or action B. Wouldn't Alice be aware that action A or B happened faster than the speed of light? And could bet on the stock market for example
This is fascinating explanation about why we can't have communication faster than light using the quantum state. Although I do have a question. You said that when we measure one particle then the other's measurement collapses in the opposite state. I wonder how long can one keep the 'measurement' alive in order to have the other particle constantly be in that opposite state. If one can do that for an arbitrary amount of time then we can make the 0 or 1 be the change from one state to another and not the state itself. So for example when I see the particle change state on my end I know that the person on the other side stopped the measurement therefor they transmitted information to me. And maybe use this to build a quantum network if it where possible. I'm thinking though that probably this can't happen and that the measurement has to be instantaneous. Pretty fun things to think about though.
sorry.. continued measurement ends entanglement.
@@lkrauss1 Thank you for answering I was really pondering on that ! Can't cheat nature after all haha.
another experiment
just assume that I entangled two particles and one has been taken by my friend in long journey. We agreed before her departure that the moment of my measure of particle state means that I say 'I love you'. So she in destination just observes if particle is still in entangled state or its wave function has been reduced to any state. Isn't it 'faster than light' communication?
th-cam.com/video/0xI2oNEc1Sw/w-d-xo.html
I just came from that video
It exactly explains why what you're saying won't work
A good demonstration of the no communication theorem. But using fast hardware quantum random number generators as an antennae plugged into a computer running software with some clever maths to demodulate randomness, this problem can be overcome. The software uses pure mathematics on true random numbers to create negative entropy and alter the laws of chance. The device achieves consistent prediction of future events well above chance level and I assume when I add cyclic redundancy code it will be 100% accurate instead of 53% over billions of results, but of course any actions based on future information will change the future so the device must have the "predict" button pressed again to see if any other future events need changing. The "Many Worlds" theorem gets you out of any causal paradox. Everything happens, but if you have the device you can make sure the bad things do not happen in your slice of the multiverse.
Quantum entanglement could change the way we communicate this will make it easy for the future communication when we try to colonize space. Let's make this discovery work for our future colonization.
No. It just means we can’t measure the results faster than light. But we really can. If you send a particle far enough away but speed of light significant you send a signal to send a signal. If you receive a response significantly faster then you should you sent information faster than light.
I could never find a clear explanation of how exactly one entangles particles or atoms... How does one actually operate with such small objects?
Also, if I spin a particle (so it points directly into the sky) while I'm Ireland and then travel with it to Australia, will the spin be pointing into the same point in the sky or will it angle?
I hope it makes sense :).
you have to look at the mathematics of quantum mechanics to understand it fully.. but basically they are entangled because together they form a single quantum state.. As far as spin.. it is not real spin like a top.. it is an intrinsic property of the particles
@@lkrauss1 We non scientists are desperately in need of an explanation for what spin actually is.
@@lkrauss1 it's not purely mathematical concept, isn't it? Something is physically happening to a particle and I try to understand what is it. Perhaps it's not possible to visualise but I wasn't to try 😉🙂
I am not sure whether I understand why quantum entanglement can't be used for faster than light communication.
If particles A and B are entangled, can Scientist A force their will into particle A? Because if they can force particle A to be in a state that can give for example:
0 0 1 0 1 1 0 0 1
then Scientist B will measure
1 1 0 1 0 0 1 1 0 and then the message will be transferred instantaneously. So if they already now that particles A and B are quantum entangled, they now that by controlling A you get an effect on B and vice versa.
Have I missed something Lawrence?
Thanks!!
no.. one cannot force the outcome of a random sequence.. quantum mechanical measurement is probabilistic
@@lkrauss1 ok now I understand why you can't transmit the info! Thanks Lawrence!!
So is there absolutely no way to manipulate a particle to create a reaction in its entangled partner's behavior? Theoretically, if possible, then you could use binary code measured over the axis, which you so very well explained(reversing the code on the receiving end of course because of the inversion). That would be immeasurable because of how fast they spin, but if signs that the "sending particle" was being manipulated (perhaps unnatural behaviors, or fluctuation in energy) you could have a computer write down the piece of binary code present in that instant on the other end, thus providing a code over a long distance, instantaneously.
Sure would be interested in hearing back from somebody on the matter. It's been puzzling me for a while.
Question:
Quantum computers can prepare qubits in states, then manipulate those states to collapse into a determined state, the result of the computation.
What would happen if you prepared entangled qubits A and B, then ship B off far away, then person at qubit A applies an operator that changes the distribution of outcomes.
If A and B did not decohere, qubit B will not have a random distribution of states when measured, right?
Where is my incorrect assumption? The measurements?
it will have a distribution of states, but a new one determined by the action on qubit A
@@lkrauss1 where does the randomness happen? Why couldn't A create an array of qubits, change the distribution like before, then B sees the effect on the distribution with enough measurements?
@@kylebowles9820 this is the only non-trivial question asked imo. i saw this exact question asked to a quantum computer guy and he couldn't give a better answer than "get out pencil & paper & try it, you won't be able to setup communication"
My *guess* is that you cannot change the quantum state of an object without local interaction.
Except for measuring an entangled object (which is random (as explained by this video)).
What I don’t get is why wouldn’t it be measured by a computer that activates alpha numeric values based on which machine experiences changed value of measurement chronologically?
A = Computer 1, quantum 1 = changed at 12:02 observed,
B = Computer 2, quantum 2 = changed 12:03
I get that it only changed when we observe it, but does a computers measurement equate the same as a humans?
That’s really what I don’t get.
Why can't observe B keep a record of what he has and just measures for change?
While it is true that we have to communicate prior, but once we set the rules for both side (for example, using ASCII as per your demonstration using 1 and 0), then in the future the two sides can be communicate based on that, wasn't it? So will that be counted as faster than light communication?
no.. random numbers carry no information
@@lkrauss1 Is that because we can't control the direction of the spin?
@@ChinPokYap results are random in this case.. that is quantum mechanics!
@@lkrauss1 i wouldn't say random numbers carry no information. they are information. but the point you're trying to make is obviously correct. random information doesn't allow communication
@@stephenkamenar I understand your point, but they trully dont carry any information. It is not information if it is trully and absolutely random, unless you change the difference of what information is. My problem is, why cant the change between collapsed / not collapsed be the information. Is there no way to tell if the electron you are receiving is collapsed or not? I thought that the double slit shows exactly that, by producing different pattern, depending on whether you measure somewhere during the experiment or not.
Will they remain entangled for eternity?
What if both cross-galactic communicators each had a nuclear clock they kept that are synchronized, and they only sent messages at specific times. That way they'll know when to expect a quantum message. Then, instead of sending values of spins directly, the sender would measure the particle at specific intervals, so that the length of the intervals between measurements themselves stood for a letter (I.e. 5 microseconds = e, 2 microsecond = b). Then, since repeated spin measurements might blur the signal (ie, 3 1's in a row look just like one very long 1), the message is repeated 10,000 times and analyzed by a computer to show exactly when each number changed to a ridiculously high level of specificity. If that's not enough, they could even standardize the message size before-hand (a galactic standard?) so they know how many characters to expect in each message.
Because of time dilation that occurs when the velocities of the two clocks are not identical ( travelling through space at different speeds and in different directions) the time expressed by the nuclear atomic clock will not match, thus the timing will not match for measurement.
What about if the observer in position A could set the bit value 0 or 1 by will? The observer in position B would then receive the bits negated. Is that not FTL information transfer (FTL communication)? That is not the correct IMHO explanation for why we cannot use QE for FTL information trnsfer. The correct reason is that the act of measurement each time breaks the entanglement.
But i think , there is still possibility of breaking causality by one way Determined Communication.
I have a plan which might work if you reply to discuss Little bit .