Thank goodness for PBS keeping hip with the times. I also liked the one about video games. Too bad it ended. Didn't really help that it started up around the same time as gamergate and didn't shy away from questions like race or gender (while covering a whole lot else too, arguably even more so than the standard identity politics discussion-- from how dating apps use gaming mechanics in their design to why Mario's jump "feels right".)
don't forget: sharkee (especially this one deserved more views) vsauce scishow veritasium sciencium asap science minute earth it's ok to be smart fermilab the good stuff stated clearly scienceetonnante (if you speak french) zefrank1 and all those other science channels i might have forgotten
There is math channel 3Blue1Brown, he is similar to PBS, talks about undergrad math (linear algebra, multivariable calculus etc) in a simple yet quite comprehensive way. I wish I knew about him back in college.
In this video we'll be using numbers. You probably don't know what those are but for the purposes of this video you just need to know they are squiggly things that math people like.
One of the best explanation of quantum I have seen in yt , cuz there are many expensive courses online which teach quantum but fail to develop a visual intuition of how quantum looks like, PBS infinite series doing a great job
weve had quantum computers for at least a year now. i started getting into coding quantum computers summer 2018 and IBM had a few quantum computers iirc, even if they had very few qbits. the top of the line quantum computers not open to public i think mighta had like 20 or 30 qbits or something, dwave has had a 2000 qbit quantum computer for a long time (uses quantum annealing, different technique from ibms computer)
in reality, there are already plenty of quantum computer out there. D wave is a Canadian company that provides quantum services to organization and Intel recently announced a 49qubit processor.
One thing that should be noted is that while computations on the entire quantum state are exponentially quicker than classical, there is still an exponential number of states that you have to observe, if you're not clever about setting things up. The reason that very specific algorithms (Shor, Grover, etc) are so much quicker is because they're able to manipulate the probabilities in a very specific manner that makes the correct answers tend to "jump out" of the final state (having a higher probability). For normal calculations, a quantum computer would be of no better use than classical.
*For normal calculations, a quantum computer would be of no better use than classical.* Or worse. A lot worse. That most people just think quantum computers = faster classical computers still blows my mind.
Why does it blow your mind? How would the average person know what a quantum computer is or even comprehend it in the slightest? You can't expect many people to get behind the idea.
I've been skimming TH-cam now for some quantum computing videos (including "You Don't Know How Quantum Computers Work") and I still can barely comprehend how it works
This is what I'm thinking that in order to take advantage of quantum computing, we basically have to redefine the very foundation of our softwares to be designed for quantum computing. In a nutshell, a quantum computer will make no difference running Crysis if we don't change the underlying software of it. The game engine, the API, the OS it runs on, etc. Also if a person just use Facebook, a quantum computer won't make significant improvements to make Facebook faster. Though there will be a changes on the backend of Facebook to process big data that in the end-user will notice if they are aware of it.
Lugmillord It takes about a minute of reading on Wikipedia to disabuse oneself of the notion. That anyone commenting on TH-cam thinks that betrays that they are too lazy to check.
I'm a senior in electrical and computer engineering at the UofA, I just understood everything she was talking about! OMG, this is amazing! Everything boils down to basics and how we can do basic things better... crazy!
imagine this logic in an AI robot at the airport making an error, "You must be detained" or "you must be executed for having water" Will i go to Jail? Probably! ;-)
Excellent exposition. Shor's Algorithm represented by quantum states, and the requisite mathematical expressions, would be a nice follow up. Thanks for your excellent work. Cheers!
It's so weird that these things exist now looking at this video from 2 years ago (still not mass produced but significantly better than when the video was made)
They exist, but not at the sizes or stability needed to actually be useful. Right now there's still just proof of concept. To actually be useful, they'd need to be orders of magnitude larger.
@@jonster337able I know you're joking, but a common mistake about how quantum computers are explained in the media is to present them as superior to regular computers, with the implication that they would be useful replacements for regular computers if they could be stably and cheaply mass produced. This implication is wrong. A quantum computer is only faster than a regular computer at certain types of computation. A regular computer generally performs one calculation at a time with extreme accuracy. To get useful results from a regular computer, it's best to use relatively efficient algorithms that perform one operation at a time. As it happens, nearly all algorithms and programs that we use are designed in this way. Also, compared to the alternative (see the next paragraph) it's much easier to design algorithms and programs in this way. A quantum computer performs hundreds to (ideally) millions of calculations in parallel with very low accuracy (you get a single state for each qubit as the outcome, but you're actually interested in the probabilities of those states). To get useful results from a quantum computer, you need to run each calculation several times (perhaps thousands or millions of times) to determine the actual probabilities of each state. Similarly, you would need to use algorithms that work best when run in parallel. Because that's what each qubit is, a parallel processor of sorts. Mathematicians have to specifically design algorithms for use with quantum computers. In other words, the things quantum computers are best at (running parallel processes) are generally not things normal computers are used for.
I love this channel! This is the first video on the subject that's made real sense to me, actually explaining beyond the concept of Schrödinger's Cat. Good job!
Thank you so much for this. I have seen so many videos that jump straight from explaining to superposition to the 2^N states thing without explaining WHY superpositions give quantum computers this power. Your vector explanation was the first thing I've seen that actually helped me understand this.
Excellent explanation! Too bad this is outdated already: starts with "Quantum computers do not exist YET ".... couldn't be so false now in October 2019. Hope we could get an update of the video.
What the IBM and google have are experimental...they won't be functional until they get more processing power...they won't declare a fully functional quantum computer until few more years...what they have now is described as "we have this much of quantum processing power"...so technically she is right....it is long before it is released as a fully functional computer...
D-Wave's computers are only by definition quantum computers, and are very different from what is typically called a "quantum computer". D-Wave's computers use quantum annealing as an optimization tool to find approximate answers to some NP-complete problems. Optimization algorithms that are inspired by annealing already exist (ie simulated annealing), but D-Wave's computers utilize "real" quantum annealing for optimization problems, instead of simulating it.
D-Wave has made some remarkable strides, but the machine they've created is very limited in scope. It can't, for example, implement Shor's algorithm. See: medium.com/quantum-bits/what-s-the-difference-between-quantum-annealing-and-universal-gate-quantum-computers-c5e5099175a1#.i248afb6k
I was just now running a program on an IBM quantum computer. And now I find a video which states, that no one has built one :-). Yea, it's from 2017, but still it entertained me. But the math still works though.
They'll probably end up being a piece of hardware attached to the motherboard of classical computer, like a graphics card, used for the types of problems it deals well with.
Basically no. From what I gather, quantum computers aren't really that great at doing 'software'. Your GPU is not that accurate, and it uses that to its advantage. Or rather; it sacrifices accuracy for speed. Your GPU doesn't need to accurately calculate everything, because in a game you'll never notice if the light isn't pixel perfect, or the color grading is 100% accurate and such. It's why workstation GPGPUs/GPUs tend to do worse in games than regular GPUs. It's because they're designed for higher precision (among many other things) and thusly are a bit slower. Basically, something designed for physics and math work will be much slower than something that can live with a moderate amount of errors/inaccuracies.
I clicked on the video thinking that this is a PBS Space Time channel and was shocked when she started to talk instead of Matt. Turns out I just found this channel and it's awesome!
The caveat at the end ( 10:50 ) is demolishing for the metaphysical interpretation of the "observer effect": if the environment (non-sentient) collapses (aka "measures", aka "interacts", aka "gets entangled") then there is no room anymore for the conscious observer being as critical as some would like. Only for that I'd applaud this video, although the rest is also pretty cool and quite well explained considering it's mostly maths.
Sphere 100 gates on outside Multiple gates open -ve just inside outside gates attract +ve optic light fed to centre of sphere Eg all gates are numbered so 1st light byte opens a gate and second byte is light to help master the software/hardware interface like old as it travels through +ve to -ve gate opening and onward Simple explanation u gave Best video yet on quantumn computing, produced yet. Cheers & Well done
Came here to say that too. Incredible, that video is almost two years old and now in 2019 not only Quantum Computers exists, but there was a Quantum Supremacy breakthrough in October. ai.googleblog.com/2019/10/quantum-supremacy-using-programmable.html?m=1
The quantum computing of today is like the very first computers of the past they are big and don't do much bit big companies are working hard to perfect it and work better
thanks for your post. I am not that much of a classical maths person, however, I see much in what what were saying relates to my work with the I Ching. The binary sequences relate directly to the four primary places of change in the I Ching. Towards the end as you were mentioning 2 to the 6th power = 64 places, is the total amount of hexagrams in the I Ching. Critical was your mention that the proposed quantum computer only takes 4 steps to return to centre as it were. In an I Ching reading, (which operates like an algorithm) returns to the centre in 3 moves. 2 moves if the initial imput is simple.
I wish you (PBS Infinite Series) wouldn't give the "quantum computers perform exponentially faster than classical" this losely, without mentioning that this isn't generally the case at all. It feeds the most common misconception about quantum computers: that they are generally exponentially faster and can solve, for example, NP-complete problems in polynomial time. They can't, and it can be proved (rigorously!) that they only can take the 2^n down to a 2^{\sqrt{n}}. It's the case only in very certain problems that exponential time is needed on a classical computer, but they can be computed in polynomial time on a quantum computer.
They can and its proofable. Here are calculations which showing the NP-Problem. They are an example which I found when I research the Arithmetical Logical Unit for NP-Heavy problems, because the ALU has some Fails which are implemented since 50 years. cosd(2,4e+1001) = 1 = Has Polynominaltime, Result can be fetched just above 1ms cosd(6,e+995) = ? = Has infinite Polynominaltime and will never spit a Result cosd(1,8e+2325) = 1 = Has no Polynominaltime, Result can be fetched below 1ms The Polynominaltime for determinate the solution for cosd(6,e+995) is with our machines infinit, because the ALU isnt able to handle infinitisemal mathematics, but the solution is 0,5.
Can someone please explain to me why after applying quantum gate to 00, the probabilities would be 1/2 for 01, 1/3 for 11 & 1/6 for 10..Much thanks in advance
Those numbers you see preceding the states when squared give the probability density of that particular state. You can do a simple reading on quantum/Schrodinger's wave equations for a better understanding.
This is one of my favourite channels, of my favorite station and favorite topic! Suggestion: It might be useful to explain briefly in a follow up video why complex numbers have twice the dimensionality of real numbers. Something like: A single complex number is made up of its real and imaginary (i^2=-1) parts, so we have two real coordinates for *both* complex numbers z and w. To illustrate, show a graph/hypercube with four real dimensions (wo for the domain and two for the range, giving a two-dimensional surface in four-dimensional space.
Don't let them fool you, you're not dead and alive at the same time. Superposition is nothing more than a "we don't know", but we can calculate exactly how big the chance is that you are in either state.
+Hilmar Zonneveld That's the Copenhagen interpretation. Bohmian mechanics says superposition is a false notion because we don't know the whole state of the system. Many worlds that all possibilities are real in other timelines, we just happen to be in the one we're at. The Copenhagen interpretation is easier to work with in the realm of quantum physics, but it doesn't say anything about even smaller scales, other interpretations will probably shed a light there in the future.
Thanks. The first explanation of quantum computing (and, more broadly, of how the principle of superposition can be used, hence isn't a mere euphemism for indeterminate) that 1) I could follow, 2) I could understand (knew a little QM coming in), 3) makes sense, and 4) seems complete (at the level of the math).
As stated you probably wont own a quantum computer in your life, but some of the practical consumer applications include data security using entanglement (look that one up, its completely unhackable), complex rendering of simulations (entire scenarios are computed at the same time) and in the near future it will improve the speeds of search engines dramatically. Lightly touched on in this video, it would take the square root of the number of searches than a classicle computer - 10000 searches for a classical computer means 100 searches for a quantum one
Except for everything related to security (and this is important with the internet) probably not much. Most stuff you want to do falls into a class of problem that have to be done sequentially so since there is nothing to parallelize you just need raw power and for that classical computer might keep the advantage by not having to deal with all the stuff that currently prevent us from having quantum computer. To go a bit technical, if you know how to solve your problem efficiently (P problems) then you don't need a quantum computer, if you currently need to do some brute force because there is no good way to solve this problem (so you need to try everything, NP-problems) then quantum computing might change this. So if you just want to play video games, nothing will change. If you want to surf on the internet, you might need a small quantum computing unit for the encryption, but otherwise you'll use a standard CPU.
I imagine, things will be more cloud based, and consumer machines will be like terminals again. As of today tech, quantum computer will be huge, taking multiple rooms like the old day computers. Internet search result is a really good example of that. For example of a video game, rather than having your console generate the 3d world, a quantum sever might able to do most of the work and your machine will only need to do some final touch and display it. Think of Siri on your phone, she doesn't know all those joke to tell you, the server does. So I think it will 1) pushes us to have even faster and bigger internet 2) new economic of quantum cpu time, perhaps (one more thing to pay after your cell data bill) 3) even cheaper, and more portable devices
Security is the killer application, I can imagine that for the consumer, it would boil down to a special purpose security chip. Just like we have GPUs and ALU, one day we might have QSU (Quantum Security Unit) that would have different instruction sets and be capable of supporting different encryption algorithms. and standard.
I've seen at least 20 videos on quantum computers that didn't explain as much as this video did - especially the detail of how calculations would work - can't believe this video is 2 years old, sheesh youtube get ur suggestion game up
Definitely the best presentation regarding accessibility to the concepts. The ordinary transfer and integration of information in our environment is FM, but the electronic processing is Digitized AM because the carrier frequencies of old AM/FM are a little less stable than the new tech. Quantum information prepared for loading into a processor is a kind of digital, "contained" in a ground state register(?) So if the information is then allowed to anneal in a coexisting context (parallel processing), whatever the combined resonance of the results, it needs to be redigitized to be meaningful, and that applies to each step. Given that I probably have no idea of exactly how this is done in practice, it is still hard to avoid the natural limitations of maintaining a coherent carrier, ground state or resonant frequency.(the brane?) I don't think anyone should stop trying, Digital tech is very impressive in the way it got around these obstacles. Engineers know that "Digital" is relative to frequencies and amplitudes regarding accuracy and stability, so to an extent, all Computation is "Quantum" pulses of resonance within pulses.
Good job simplifying something as complex as quantum computing. That sphere representation is right on spot! Although the comments below shows that not many people can grasp the concept yet. I've seen a lot of videos about this subject as I am really into it, at an amateur level. Math is not my strong suit, yet I love computing as it's the easiest way to use cutting edge Math researches for scientific applications. Neuroscientists recently discovered that brain cells operate on a quantum model of 11 dimensions. That's a funny coincidence since astrophysicists also discovered a while ago that the universe itself is a 11 dimensions model, or at least was at it's origin, according to string theory, if I am not wrong. I have just subscribed to your channel but giving the name and the comment section at the end of this video, I take it you mainly deal with maths and you give coding challenges to your followers. That's cool stuff but how about a collaboration with another science streamer, such as a neurophysic or astrophysic channel? Would that not be great? Maths are a amazing when applied to the real world, at least to me ;) Anyhow keep up the good work!
D-Wave has made some remarkable strides, but the machine they've created is very limited in scope. It can't, for example, implement Shor's algorithm. See: medium.com/quantum-bits/what-s-the-difference-between-quantum-annealing-and-universal-gate-quantum-computers-c5e5099175a1#.i248afb6k
Hold on. What is the D-Wave 2000Q? Is not even research level but commercial hardware. According to Wikipedia, there are quite some Quantum Computers and 2 very good ones and reprogramables for 2016. What is wrong here? Do they understand Quantum Computers different than you Kelsey? Thanks in advance for the kind response.
D-wave is a special purpose computer - it is hard-wired to solve only one type of problem. And it's also crappy at doing so - it has speed comparable to average notebook and with only a fraction of precision and versatility.
Agree with +Bradly Drawn Turtle and +KohuGaly, however, there is supposed to be some quantum machines right now regardless of D-Wave: -University of Maryland, reprogramable quantum computer. -Nasa aquired with Google a Quantum Computer, it's performance is widely accepted -etc....
Can dwave do simple math of a simple calculator? Right now quantum computing seems like Theranos. An exercise in attracting research money. Most of the money probably goes to low temperature physics research. The Chinese are following the logical path in quantum computing by studying it using light instead of low temperature.
Would this prove that the Copenhagen interpretation is actually true? I mean, for this to work the quantum particle needs to be *actually* in a superposition state? Or the probabilities will work even if it is not really the case but we treat it as it is? I mean is there any difference between a particle having 80% chance of being in one state and 20% of being on the other, vs being *actually* on a 80/20 superposition? I hope mi questions make sense...
Forget the Copenhagen interpretation. Since QFT, we really don't think about particles as particles, we only think about fields interacting. The "lump" in energy (quanta) rises what we observe as a particle. The "collapse" of the wave function is just the entanglement. That's why it was specified that the noise of the environment presents a serious threat since it can entangle the qubits and screw everything up. And that's why we need to keep it really... really... cool.
Wow, wow, wow... stop! Superpositions have nothing to do with the collapse of the schrödinger wave equation! 2 Waves with a Wavelength difference of 1/2 and traveling in each others direction will form a Standing Wave. A Standing Wave is a Mix State between 2 waves. For example: Wave0 = Eigenvalue +1 = From Right to Left Wave1 = Eigenvalue -1 = From Left to Right +1-1 = ±1 ≠ 0 Entanglement is for example mathematicly this: cos(45°) + sin(45°) = cos(π/4) + sin(π/4) = 1/√2 en.wikipedia.org/wiki/Bloch_sphere en.wikipedia.org/wiki/Qubit#Entanglement Every particle has conserved quantities and this is what the information represents. Its possible to measure for example the mass or velocity. Here you can read about the exact Laws: en.wikipedia.org/wiki/Conservation_law#Exact_laws I personally work with the weak Isospin of Particles over the symmetrical unitary group 2 "SU(2)". en.wikipedia.org/wiki/Unitary_group
Interpretations cannot be found to be true or false, because they make no predictions that can be tested. Yes, if a quantum computer can ever work, it must achieve superposition.
A bit made by a semitransitor can have two values: transmitting electron (1) or hardly transmitting electron (0). If we have two bit, we can have 2^2 values: 00, 11, 01, 10. A qubit made by an electron can have three values: up (1), down (0), mix (s). So if we have two qubit, we can have 2^3 values: 00, 11, 10, 01, ss, 0s, s0, 1s, s1. So qubit (if it can be harnessed) can store data much more effectively. It can also push the speed of calculating because a "s" and a 1 or 0 can happen at the same time.
Awesome explanation, thank you. This really has helped me to understand more clearly what is meant when people talk about parallelism in quantum computing. :)
Th whole point of computers is surity and confidence in the calculations it performs. How can you expect a calculation with a probabilistic outcome to represent anything real. I.E. how can we even use those numbers..if they are probabilistic???
Yes, Quantum Computers are probabilistic, not deterministic. However, the benefit of this approach is that there are very specific cases where you can create a gate network that will assign a high probability to the "correct" calculation. What's the use of this, you might ask? There are problems that take enormously long times to solve in a deterministic manner (eg. factoring), and if you can instead get the number after repeating a quantum algorithm a number of times to find the right answer, it's a huge speed up. Yeah, you'll get the wrong answer a bunch of times, but the you've got classical computers to check the answer and when you finally DO get the correct answer, the total time taken will be much much lower than solving the original problem on a classical computer.
They are probabilistic, but as they said, you don't just run it once and call it done. You run it as many times as necessary to settle on a result. Not unlike flipping a coin enough times in the same way to eventually arrive at a point where it is statistically extremely unlikely that the coin's probability of landing on either side is not 50/50 (or 49.99999999999999999999/50.00000000000000000001, as the case may be). Try not to think about it in classical terms. Quantum computers aren't for doing classical calculations (in fact they are typically several orders of magnitude slower than classical computers when doing things that classical computers are good at, like multiplying integers).
Let's take factoring for example, as that's the big win for QC. I'm simplifying things here a lot, but this should be okay for illustration. Let's say you get an answer "1234567 is a factor of this big number". You can take a classical computer and do out the division normally. If there's no remainder, then you can say that the quantum computer was right, 1234567 IS the factor we've been looking for! If not, it should be very quick to see that the answer popped out was incorrect, so try again.
you make me feel that i know math!!! :) btw keep moving your hands like you do, i don't no why but it really calm me down when things are getting complicated and so i can get back on track, finish the video and learn sonething, almost like you are taking us to a step-by-step learning with your hands ^^ thanks a lot, great video about something that i thought i would never understand...
In the description of a quantum computer can we please stop using the bit as the starting point. What makes computers easy to grok is the fact that they are based in switches. This isn't an analogy, they are literally switches. And that each switch has an on and an off state. Now, with that as a starting point, can someone put forth a description of a. Quantum computer that explains the mechanism behind a qubit, and please do better than just saying spin. I know this is a math channel, but with a masters in computer science, I need to know something of the physicality of the device to follow the logic. And no one ever goes into the details of how the quantum machines work.
Watch and Read this in the order I gave you: en.wikipedia.org/wiki/Interferometry en.wikipedia.org/wiki/Quantum_entanglement en.wikipedia.org/wiki/Quadrature_amplitude_modulation th-cam.com/video/7Rtqbygk7Qk/w-d-xo.html th-cam.com/video/zcqZHYo7ONs/w-d-xo.html en.wikipedia.org/wiki/Chirality_(physics) I have allready concepted a logical circuit which is able to register time correlated bits.
In a classical computer, the data are conveyed via data paths from storage devices, through gates, and back to storage. So the gates are physically separate from the storage (although not far away). In a quantum computer, a state is in a storage device, and microwaves are directed at it that device cause it to perform a gate function on the state stored in it. So the same device functions as storage and gates.
Matthew, this is an excellent question. In a normal computer the switches are formed by MOS transistors. And these MOSTs act as controllable switches. With drawing a schematic out of MOSTs you can see e.g. how a more complex gate like NOT or AND is formed. It would be great to have such schematic for a quantum gate. But I think currently such qbit gates are not formed by such MOSTs, but by a kind of physical testbench so that physics acts as a quantum gates, or even as a cascade of it. Unfortunately in such testbench there are no MOS transistor switches, and you need temparatures close to few Kelvins.
I would love to see more about applications of these things. I know math doesn't necessarily do that and I understand the videos just fine, I would love to see more about the differences from general computers, for example. Like in the factorization example, compare the two methods? Just something to think about. Otherwise neat vid, loving this channel so far~~
a little bit of nit picking: I dont expect that any non-german speaker can pronounce Schrödinger correctly; but for a good scientific standard you should at least write his name right, i.e., with an "ö" instead of an "o".
As a very lay man, below average Id say in the math department, this is absolutely amazing! if we could actually make a quantum computer the difference would be something like before Alan Turing invented his Turing machine, and its aftermath! loving this stuff, thank you!.
Definitely the best video I've seen on quantum computing, great job! Although, I would have mentioned that it is interference that gives you the huge speed up.
Argh don't you dare throw theses evil physicist words around. But seriously, isn't intererence and superposition the absolute same in this case? I'm curious
Ah, good question, but they are not the same. A superposition is when you have a state that is a combination of other states. This isn't some mathy trick though, the multiple states are really there and they can interact with each other. That interaction is interference. Think of foil from high school: (a+b)^2 = a^2 + 2ab + b^2, you can imagine that the 2ab term is an interference between a and b. Hope that helped.
hmmm, ok consider this. Any state can be represented as a linear combination of eigenbasis vectors, such that the sum of the complex squares adds up to 1. Your state is in a superposition if it gives multiple eigenbasis vectors non-zero coefficients. Now if you want to know the probability of your state transitioning into some other superposition state, you compute an inner product. In the quantum mechanical formulation you will get extra terms in that inner product that you wouldn't get classically, those extra terms are the interference. Wikipedia has a nice quick description: en.wikipedia.org/wiki/Interference_(wave_propagation)#Quantum_interference
Update to 27 January 2019 - there are quantum computers in production (albeit, coherence is questionable) - IBM, Rigetti, D-Wave (annealing), Google, AliBaba and others have working QC's
Excellent explanation! if you have no control on what state a qubit(s) can be, how can you assign different probabilities to each state? In @3:30, was state |00> eliminated because it is the basic state, or is it purposefully given a zero probability? Another question, in @9:09 what do you exactly mean by 4 "steps" (runs?)? Thank you!
wait, so how do you take the value from the qubit if part of it is imaginary? or do you just take ignore the imaginary part and get the absolute value of the real part?
Infinite series and spacetime are the best thing to happen to youtube...
Don't forget Idea Channel!
Thank goodness for PBS keeping hip with the times.
I also liked the one about video games. Too bad it ended. Didn't really help that it started up around the same time as gamergate and didn't shy away from questions like race or gender (while covering a whole lot else too, arguably even more so than the standard identity politics discussion-- from how dating apps use gaming mechanics in their design to why Mario's jump "feels right".)
don't forget:
sharkee (especially this one deserved more views)
vsauce
scishow
veritasium
sciencium
asap science
minute earth
it's ok to be smart
fermilab
the good stuff
stated clearly
scienceetonnante (if you speak french)
zefrank1
and all those other science channels i might have forgotten
Dennis Haupt i thought that zefrank was inactive.
There is math channel 3Blue1Brown, he is similar to PBS, talks about undergrad math (linear algebra, multivariable calculus etc) in a simple yet quite comprehensive way. I wish I knew about him back in college.
This was maybe the most well-put explanation of quantum computing I've seen on TH-cam or really anywhere. Thanks for this!
She: Quantum computer's don't exist yet
Me: in 2021 jumps into to description box to see when was the video uploaded 😂
Same lol
me in 2024 too
@@agaggaaggegeit's been 2 years i commented this 😭 it feels like i did just 2 months a ago 😭
@@Lonewolf-haha, time is flying 😂
In this video we'll be using numbers. You probably don't know what those are but for the purposes of this video you just need to know they are squiggly things that math people like.
[snicker]
2:11 "Actually, qubits are not made of cats" - my world collapsed like a wave function :-(
and Qbert is an old game from the 80's
Maybe not, but you can take Fourier transformations of them:
xkcd.com/26/
+
Don't worry wiadroman, the internet is still made of cats.
+
One of the best explanation of quantum I have seen in yt , cuz there are many expensive courses online which teach quantum but fail to develop a visual intuition of how quantum looks like, PBS infinite series doing a great job
_2017: Nobody has ever built a Quantum Computer!!_
_2019: Hold my Qubits_
weve had quantum computers for at least a year now. i started getting into coding quantum computers summer 2018 and IBM had a few quantum computers iirc, even if they had very few qbits. the top of the line quantum computers not open to public i think mighta had like 20 or 30 qbits or something, dwave has had a 2000 qbit quantum computer for a long time (uses quantum annealing, different technique from ibms computer)
@@matthewtrebs9738 from where we learn qbits link please
"useful quantum computer"
There are two now that exist in the world
in reality, there are already plenty of quantum computer out there. D wave is a Canadian company that provides quantum services to organization and Intel recently announced a 49qubit processor.
So much has happened since 2017...
Read the date
DWave does not use a quantum computer. It uses quantum annealing, not a true series of quantum gates.
hello wonderful person! its weird to see you here lol
Yes but hazardous collapse of process still very high, so all are not reliable
One thing that should be noted is that while computations on the entire quantum state are exponentially quicker than classical, there is still an exponential number of states that you have to observe, if you're not clever about setting things up. The reason that very specific algorithms (Shor, Grover, etc) are so much quicker is because they're able to manipulate the probabilities in a very specific manner that makes the correct answers tend to "jump out" of the final state (having a higher probability). For normal calculations, a quantum computer would be of no better use than classical.
*For normal calculations, a quantum computer would be of no better use than classical.*
Or worse. A lot worse. That most people just think quantum computers = faster classical computers still blows my mind.
Why does it blow your mind? How would the average person know what a quantum computer is or even comprehend it in the slightest? You can't expect many people to get behind the idea.
I've been skimming TH-cam now for some quantum computing videos (including "You Don't Know How Quantum Computers Work") and I still can barely comprehend how it works
This is what I'm thinking that in order to take advantage of quantum computing, we basically have to redefine the very foundation of our softwares to be designed for quantum computing.
In a nutshell, a quantum computer will make no difference running Crysis if we don't change the underlying software of it. The game engine, the API, the OS it runs on, etc. Also if a person just use Facebook, a quantum computer won't make significant improvements to make Facebook faster. Though there will be a changes on the backend of Facebook to process big data that in the end-user will notice if they are aware of it.
Lugmillord It takes about a minute of reading on Wikipedia to disabuse oneself of the notion. That anyone commenting on TH-cam thinks that betrays that they are too lazy to check.
I'm a senior in electrical and computer engineering at the UofA, I just understood everything she was talking about! OMG, this is amazing! Everything boils down to basics and how we can do basic things better... crazy!
Quantum SatNav computer. "Turn left at the next junction. Probably".
imagine this logic in an AI robot at the airport making an error, "You must be detained" or "you must be executed for having water" Will i go to Jail? Probably! ;-)
Thank goodness for TH-cam. How else can we have access to such amazing teachers.
This is the best short explanation of quantum computing. Thank you!
Excellent exposition. Shor's Algorithm represented by quantum states, and the requisite mathematical expressions, would be a nice follow up. Thanks for your excellent work. Cheers!
It's so weird that these things exist now looking at this video from 2 years ago (still not mass produced but significantly better than when the video was made)
Only one quantum computer needs to be built. After that it'll build itself.
They exist, but not at the sizes or stability needed to actually be useful. Right now there's still just proof of concept. To actually be useful, they'd need to be orders of magnitude larger.
@@jonster337able I know you're joking, but a common mistake about how quantum computers are explained in the media is to present them as superior to regular computers, with the implication that they would be useful replacements for regular computers if they could be stably and cheaply mass produced. This implication is wrong. A quantum computer is only faster than a regular computer at certain types of computation.
A regular computer generally performs one calculation at a time with extreme accuracy. To get useful results from a regular computer, it's best to use relatively efficient algorithms that perform one operation at a time. As it happens, nearly all algorithms and programs that we use are designed in this way. Also, compared to the alternative (see the next paragraph) it's much easier to design algorithms and programs in this way.
A quantum computer performs hundreds to (ideally) millions of calculations in parallel with very low accuracy (you get a single state for each qubit as the outcome, but you're actually interested in the probabilities of those states). To get useful results from a quantum computer, you need to run each calculation several times (perhaps thousands or millions of times) to determine the actual probabilities of each state. Similarly, you would need to use algorithms that work best when run in parallel. Because that's what each qubit is, a parallel processor of sorts. Mathematicians have to specifically design algorithms for use with quantum computers.
In other words, the things quantum computers are best at (running parallel processes) are generally not things normal computers are used for.
Finally a video on quantum computing that didn’t skip over the math and dumb it down too much. THANK YOU.
I love this channel! This is the first video on the subject that's made real sense to me, actually explaining beyond the concept of Schrödinger's Cat. Good job!
Just started rewatching these videos. Thank you Kelsey.
great video! One of the best intros to qubits and quantum computing (especially its underlying math) that I have seen. Thank you!
Thank you so much for this. I have seen so many videos that jump straight from explaining to superposition to the 2^N states thing without explaining WHY superpositions give quantum computers this power. Your vector explanation was the first thing I've seen that actually helped me understand this.
Best explanation I've seen so far... And I've seen quite a few!
I have no idea what 90% of these things are yet I still enjoy watching this
Excellent explanation!
Too bad this is outdated already: starts with "Quantum computers do not exist YET ".... couldn't be so false now in October 2019. Hope we could get an update of the video.
The series ended in May 2018 so we won't get an update : (
So apart from that statement, what needs updating?
What the IBM and google have are experimental...they won't be functional until they get more processing power...they won't declare a fully functional quantum computer until few more years...what they have now is described as "we have this much of quantum processing power"...so technically she is right....it is long before it is released as a fully functional computer...
I feel like it was false when this video was published too.
I love whomever is coaching your hand movements between this and Spacetime. No Sarcasm. Your shows are incredible. :)
I think D-Wave would argue against your opening point of quantum computers not existing.
We can't be certain that quantum computers don't exist; it is both existent and nonexistent until you go to everyone and ask.
Oliver Hees I see what you did there. LOL
D-Wave's computers are only by definition quantum computers, and are very different from what is typically called a "quantum computer". D-Wave's computers use quantum annealing as an optimization tool to find approximate answers to some NP-complete problems. Optimization algorithms that are inspired by annealing already exist (ie simulated annealing), but D-Wave's computers utilize "real" quantum annealing for optimization problems, instead of simulating it.
D-Wave has made some remarkable strides, but the machine they've created is very limited in scope. It can't, for example, implement Shor's algorithm. See: medium.com/quantum-bits/what-s-the-difference-between-quantum-annealing-and-universal-gate-quantum-computers-c5e5099175a1#.i248afb6k
lmao genius
This is *by far* the best content on internet I ever found explaining how a Quantum computer works. Gratitude.
don't understand everything but still love hearing the explanation
I was just now running a program on an IBM quantum computer. And now I find a video which states, that no one has built one :-). Yea, it's from 2017, but still it entertained me. But the math still works though.
she's actually a very good teacher.
Very good video! You present complex concepts pertaining to quantum computers in a very intuitive way. Good job!
But can it run Crysis?
I think this one just might.
Nope, it cannot. Quantum computers will not be very good at running game like applications sadly..
They'll probably end up being a piece of hardware attached to the motherboard of classical computer, like a graphics card, used for the types of problems it deals well with.
No, but it would be pretty good at dynamic enemy AI
Basically no. From what I gather, quantum computers aren't really that great at doing 'software'.
Your GPU is not that accurate, and it uses that to its advantage. Or rather; it sacrifices accuracy for speed. Your GPU doesn't need to accurately calculate everything, because in a game you'll never notice if the light isn't pixel perfect, or the color grading is 100% accurate and such.
It's why workstation GPGPUs/GPUs tend to do worse in games than regular GPUs. It's because they're designed for higher precision (among many other things) and thusly are a bit slower.
Basically, something designed for physics and math work will be much slower than something that can live with a moderate amount of errors/inaccuracies.
I clicked on the video thinking that this is a PBS Space Time channel and was shocked when she started to talk instead of Matt. Turns out I just found this channel and it's awesome!
2:10 That's it... I'm naming my cat Qubit
Just found out about this channel and I am really enjoying it. Keep up the great content! This stuff is so fascinating.
The matrix shown at 7:20 under the label"unitary matrix" isn't unitary.
But it's quasi-unitary, which means that it's unitary up to a typo.
Best comment xd
Zardo: Yes! Now that we fixed it with annotations is it almost-quasi-unitary?
The annotations are translucent, so it's now a superposition of unitary and quasi-unitary.
8:57 It should be 6-dimensional and not 64 dimensional
Quantum computing is great for calculating a program location scene on the Holodeck on the Starship Enterprise (before it was destroyed).
1/2 way through I can't remember how many times she said "I'll get back to that ."
Finally I found an explanation of quantum computing that kinda makes sense!
Thank you
The power of abstraction, nerds.
The caveat at the end ( 10:50 ) is demolishing for the metaphysical interpretation of the "observer effect": if the environment (non-sentient) collapses (aka "measures", aka "interacts", aka "gets entangled") then there is no room anymore for the conscious observer being as critical as some would like. Only for that I'd applaud this video, although the rest is also pretty cool and quite well explained considering it's mostly maths.
Be careful with the red border on the bottom of the video thumbnail. TH-cam uses a similar looking bar for their amount-played.
I was definitely disappointed when i saw the thumbnail, because i much prefer to see the thumbnail that says i haven't watched it.
Sphere
100 gates on outside
Multiple gates open
-ve just inside outside gates attract +ve optic light fed to centre of sphere
Eg all gates are numbered so 1st light byte opens a gate and second byte is light to help master the software/hardware interface like old as it travels through +ve to -ve gate opening and onward
Simple explanation u gave Best video yet on quantumn computing, produced yet. Cheers & Well done
*i was going to tell you a quantum joke* but its funny and not funny at the same time
@Alfie One electron laughs at the joke the other cries.
When it was written, it was funny. But when it was read, it wasn't funny.
Almost laughing in superposition of both states :-)
It’s not even funny how funny it is!
I'm not observing it so it's undecided.
Finally, a simple and elegant explanation of quantum computing. Thanks Infinite Series.
How fast we move. This video is from 2017 and now in 2019 we have quantum computers. How long before an AI singularity?
Came here to say that too. Incredible, that video is almost two years old and now in 2019 not only Quantum Computers exists, but there was a Quantum Supremacy breakthrough in October.
ai.googleblog.com/2019/10/quantum-supremacy-using-programmable.html?m=1
The quantum computing of today is like the very first computers of the past they are big and don't do much bit big companies are working hard to perfect it and work better
thanks for your post. I am not that much of a classical maths person, however, I see much in what what were saying relates to my work with the I Ching. The binary sequences relate directly to the four primary places of change in the I Ching. Towards the end as you were mentioning 2 to the 6th power = 64 places, is the total amount of hexagrams in the I Ching. Critical was your mention that the proposed quantum computer only takes 4 steps to return to centre as it were. In an I Ching reading, (which operates like an algorithm) returns to the centre in 3 moves. 2 moves if the initial imput is simple.
I wish you (PBS Infinite Series) wouldn't give the "quantum computers perform exponentially faster than classical" this losely, without mentioning that this isn't generally the case at all. It feeds the most common misconception about quantum computers: that they are generally exponentially faster and can solve, for example, NP-complete problems in polynomial time. They can't, and it can be proved (rigorously!) that they only can take the 2^n down to a 2^{\sqrt{n}}. It's the case only in very certain problems that exponential time is needed on a classical computer, but they can be computed in polynomial time on a quantum computer.
They can and its proofable.
Here are calculations which showing the NP-Problem. They are an example which I found when I research the Arithmetical Logical Unit for NP-Heavy problems, because the ALU has some Fails which are implemented since 50 years.
cosd(2,4e+1001) = 1 = Has Polynominaltime, Result can be fetched just above 1ms
cosd(6,e+995) = ? = Has infinite Polynominaltime and will never spit a Result
cosd(1,8e+2325) = 1 = Has no Polynominaltime, Result can be fetched below 1ms
The Polynominaltime for determinate the solution for cosd(6,e+995) is with our machines infinit, because the ALU isnt able to handle infinitisemal mathematics, but the solution is 0,5.
I like the music that started playing when you started talking about vectors.
Can quantum computers exist and not exist at the same time ??
Maybe, maybe not. We don't know.
Chicken before the egg type question
Joy Moody but- evolution
Depends on whether or not you are observing it.
Devil's Advocate
yes "they" can but actually its he, not they.
Excellent video and I think I am beginning to understand. The very best explanation I have seen so far and I have viewed and read many. Thank you
Can someone please explain to me why after applying quantum gate to 00, the probabilities would be 1/2 for 01, 1/3 for 11 & 1/6 for 10..Much thanks in advance
its just an example of what it could change to. They have just made up random numbers for the purpose of demonstration. (I think)
Those numbers you see preceding the states when squared give the probability density of that particular state. You can do a simple reading on quantum/Schrodinger's wave equations for a better understanding.
Excellent explanation of Quantum Computation within a short time
2019 Hold my Beer!
This is one of my favourite channels, of my favorite station and favorite topic! Suggestion: It might be useful to explain briefly in a follow up video why complex numbers have twice the dimensionality of real numbers. Something like: A single complex number is made up of its real and imaginary (i^2=-1) parts, so we have two real coordinates for *both* complex numbers z and w. To illustrate, show a graph/hypercube with four real dimensions (wo for the domain and two for the range, giving a two-dimensional surface in four-dimensional space.
Show me how to write “Hello world!”
🥴🥴🥴🥴
You've explained this better than anyone else I have seen.
Meow!
:D
Don't let them fool you, you're not dead and alive at the same time. Superposition is nothing more than a "we don't know", but we can calculate exactly how big the chance is that you are in either state.
+Hilmar Zonneveld
Treating the collapse of the wave function as a physical event also leads to contradictions.
+Hilmar Zonneveld That's the Copenhagen interpretation. Bohmian mechanics says superposition is a false notion because we don't know the whole state of the system. Many worlds that all possibilities are real in other timelines, we just happen to be in the one we're at. The Copenhagen interpretation is easier to work with in the realm of quantum physics, but it doesn't say anything about even smaller scales, other interpretations will probably shed a light there in the future.
I said the same thing when I first saw her...
Miau!
Thanks. The first explanation of quantum computing (and, more broadly, of how the principle of superposition can be used, hence isn't a mere euphemism for indeterminate) that 1) I could follow, 2) I could understand (knew a little QM coming in), 3) makes sense, and 4) seems complete (at the level of the math).
If quantum calculations result in multiple solutions based on probabilities how do we know which solution is the correct one?
HollowMoose we test it
its the one with the highest amplitude
Best explanation found in anywhere. Thanks. Really.
How would a quantum computer change computing for the consumer?
This probably will not be a technology that would end up in general purpose consumer computers.
As stated you probably wont own a quantum computer in your life, but some of the practical consumer applications include data security using entanglement (look that one up, its completely unhackable), complex rendering of simulations (entire scenarios are computed at the same time) and in the near future it will improve the speeds of search engines dramatically. Lightly touched on in this video, it would take the square root of the number of searches than a classicle computer - 10000 searches for a classical computer means 100 searches for a quantum one
Except for everything related to security (and this is important with the internet) probably not much. Most stuff you want to do falls into a class of problem that have to be done sequentially so since there is nothing to parallelize you just need raw power and for that classical computer might keep the advantage by not having to deal with all the stuff that currently prevent us from having quantum computer. To go a bit technical, if you know how to solve your problem efficiently (P problems) then you don't need a quantum computer, if you currently need to do some brute force because there is no good way to solve this problem (so you need to try everything, NP-problems) then quantum computing might change this.
So if you just want to play video games, nothing will change. If you want to surf on the internet, you might need a small quantum computing unit for the encryption, but otherwise you'll use a standard CPU.
I imagine, things will be more cloud based, and consumer machines will be like terminals again. As of today tech, quantum computer will be huge, taking multiple rooms like the old day computers.
Internet search result is a really good example of that. For example of a video game, rather than having your console generate the 3d world, a quantum sever might able to do most of the work and your machine will only need to do some final touch and display it.
Think of Siri on your phone, she doesn't know all those joke to tell you, the server does.
So I think it will
1) pushes us to have even faster and bigger internet
2) new economic of quantum cpu time, perhaps (one more thing to pay after your cell data bill)
3) even cheaper, and more portable devices
Security is the killer application, I can imagine that for the consumer, it would boil down to a special purpose security chip. Just like we have GPUs and ALU, one day we might have QSU (Quantum Security Unit) that would have different instruction sets and be capable of supporting different encryption algorithms. and standard.
I've seen at least 20 videos on quantum computers that didn't explain as much as this video did - especially the detail of how calculations would work - can't believe this video is 2 years old, sheesh youtube get ur suggestion game up
tell us the story about the square on your left middle finger :D
its the story of my life
Definitely the best presentation regarding accessibility to the concepts.
The ordinary transfer and integration of information in our environment is FM, but the electronic processing is Digitized AM because the carrier frequencies of old AM/FM are a little less stable than the new tech.
Quantum information prepared for loading into a processor is a kind of digital, "contained" in a ground state register(?)
So if the information is then allowed to anneal in a coexisting context (parallel processing), whatever the combined resonance of the results, it needs to be redigitized to be meaningful, and that applies to each step.
Given that I probably have no idea of exactly how this is done in practice, it is still hard to avoid the natural limitations of maintaining a coherent carrier, ground state or resonant frequency.(the brane?)
I don't think anyone should stop trying, Digital tech is very impressive in the way it got around these obstacles. Engineers know that "Digital" is relative to frequencies and amplitudes regarding accuracy and stability, so to an extent, all Computation is "Quantum" pulses of resonance within pulses.
what's your Erdös number?
Mine's g64.
+
Good job simplifying something as complex as quantum computing. That sphere representation is right on spot! Although the comments below shows that not many people can grasp the concept yet.
I've seen a lot of videos about this subject as I am really into it, at an amateur level. Math is not my strong suit, yet I love computing as it's the easiest way to use cutting edge Math researches for scientific applications. Neuroscientists recently discovered that brain cells operate on a quantum model of 11 dimensions. That's a funny coincidence since astrophysicists also discovered a while ago that the universe itself is a 11 dimensions model, or at least was at it's origin, according to string theory, if I am not wrong.
I have just subscribed to your channel but giving the name and the comment section at the end of this video, I take it you mainly deal with maths and you give coding challenges to your followers. That's cool stuff but how about a collaboration with another science streamer, such as a neurophysic or astrophysic channel?
Would that not be great?
Maths are a amazing when applied to the real world, at least to me ;)
Anyhow keep up the good work!
d wave
D-Wave has made some remarkable strides, but the machine they've created is very limited in scope. It can't, for example, implement Shor's algorithm. See: medium.com/quantum-bits/what-s-the-difference-between-quantum-annealing-and-universal-gate-quantum-computers-c5e5099175a1#.i248afb6k
First time I truly understood quantum computation. Great job!
Hold on. What is the D-Wave 2000Q? Is not even research level but commercial hardware. According to Wikipedia, there are quite some Quantum Computers and 2 very good ones and reprogramables for 2016. What is wrong here? Do they understand Quantum Computers different than you Kelsey? Thanks in advance for the kind response.
Also according to Wikipedia, independent researchers are doubtful of D-Wave's claims.
D-wave is a special purpose computer - it is hard-wired to solve only one type of problem. And it's also crappy at doing so - it has speed comparable to average notebook and with only a fraction of precision and versatility.
Agree with +Bradly Drawn Turtle and +KohuGaly, however, there is
supposed to be some quantum machines right now regardless of D-Wave:
-University of Maryland, reprogramable quantum computer.
-Nasa aquired with Google a Quantum Computer, it's performance is widely accepted
-etc....
erparom
The ones at Google and NASA are just D-Waves.
Can dwave do simple math of a simple calculator?
Right now quantum computing seems like Theranos.
An exercise in attracting research money.
Most of the money probably goes to low temperature physics research.
The Chinese are following the logical path in quantum computing by studying it using light instead of low temperature.
One of The Best Explanation of Quantum Computers.
I can tell you 2 is a factor of the number.
And the rest? ;)
The comment box is too small for this factorization.
Damn youtube
It's also divisible by 3.
Best video about mathematical quantum computing I've seen yet.
Keep it up!
Would this prove that the Copenhagen interpretation is actually true?
I mean, for this to work the quantum particle needs to be *actually* in a superposition state? Or the probabilities will work even if it is not really the case but we treat it as it is?
I mean is there any difference between a particle having 80% chance of being in one state and 20% of being on the other, vs being *actually* on a 80/20 superposition?
I hope mi questions make sense...
I'm pretty sure there is no differenece
Forget the Copenhagen interpretation. Since QFT, we really don't think about particles as particles, we only think about fields interacting. The "lump" in energy (quanta) rises what we observe as a particle.
The "collapse" of the wave function is just the entanglement. That's why it was specified that the noise of the environment presents a serious threat since it can entangle the qubits and screw everything up. And that's why we need to keep it really... really... cool.
burt591 take a look on Bell inequalities, he asked the same question, i believe
Wow, wow, wow... stop!
Superpositions have nothing to do with the collapse of the schrödinger wave equation! 2 Waves with a Wavelength difference of 1/2 and traveling in each others direction will form a Standing Wave. A Standing Wave is a Mix State between 2 waves.
For example:
Wave0 = Eigenvalue +1 = From Right to Left
Wave1 = Eigenvalue -1 = From Left to Right
+1-1 = ±1 ≠ 0
Entanglement is for example mathematicly this:
cos(45°) + sin(45°) = cos(π/4) + sin(π/4) = 1/√2
en.wikipedia.org/wiki/Bloch_sphere
en.wikipedia.org/wiki/Qubit#Entanglement
Every particle has conserved quantities and this is what the information represents. Its possible to measure for example the mass or velocity.
Here you can read about the exact Laws:
en.wikipedia.org/wiki/Conservation_law#Exact_laws
I personally work with the weak Isospin of Particles over the symmetrical unitary group 2 "SU(2)".
en.wikipedia.org/wiki/Unitary_group
Interpretations cannot be found to be true or false, because they make no predictions that can be tested.
Yes, if a quantum computer can ever work, it must achieve superposition.
A bit made by a semitransitor can have two values: transmitting electron (1) or hardly transmitting electron (0). If we have two bit, we can have 2^2 values: 00, 11, 01, 10.
A qubit made by an electron can have three values: up (1), down (0), mix (s). So if we have two qubit, we can have 2^3 values: 00, 11, 10, 01, ss, 0s, s0, 1s, s1.
So qubit (if it can be harnessed) can store data much more effectively. It can also push the speed of calculating because a "s" and a 1 or 0 can happen at the same time.
IBM built one, this video probably outdated and every one can access it for an experiment
when?
@@guitar300k well here is a discussion about it from 2017 th-cam.com/video/JRIPV0dPAd4/w-d-xo.html
I was there for Francis Su's speech! And I agree, it was really really good.
I thought you didn't want to be limited to reality
Quantum computers aren't real. (And never will be.)
The field is quite new, and quantum computers are possible, so I would not think that...
Awesome explanation, thank you. This really has helped me to understand more clearly what is meant when people talk about parallelism in quantum computing. :)
Th whole point of computers is surity and confidence in the calculations it performs. How can you expect a calculation with a probabilistic outcome to represent anything real. I.E. how can we even use those numbers..if they are probabilistic???
That's what I don't get either... Does quantum computing mean that if for example you multiply two integers it sometimes gives you the wrong answer?
Yes, Quantum Computers are probabilistic, not deterministic. However, the benefit of this approach is that there are very specific cases where you can create a gate network that will assign a high probability to the "correct" calculation. What's the use of this, you might ask? There are problems that take enormously long times to solve in a deterministic manner (eg. factoring), and if you can instead get the number after repeating a quantum algorithm a number of times to find the right answer, it's a huge speed up. Yeah, you'll get the wrong answer a bunch of times, but the you've got classical computers to check the answer and when you finally DO get the correct answer, the total time taken will be much much lower than solving the original problem on a classical computer.
They are probabilistic, but as they said, you don't just run it once and call it done. You run it as many times as necessary to settle on a result. Not unlike flipping a coin enough times in the same way to eventually arrive at a point where it is statistically extremely unlikely that the coin's probability of landing on either side is not 50/50 (or 49.99999999999999999999/50.00000000000000000001, as the case may be).
Try not to think about it in classical terms. Quantum computers aren't for doing classical calculations (in fact they are typically several orders of magnitude slower than classical computers when doing things that classical computers are good at, like multiplying integers).
Let's take factoring for example, as that's the big win for QC. I'm simplifying things here a lot, but this should be okay for illustration. Let's say you get an answer "1234567 is a factor of this big number". You can take a classical computer and do out the division normally. If there's no remainder, then you can say that the quantum computer was right, 1234567 IS the factor we've been looking for! If not, it should be very quick to see that the answer popped out was incorrect, so try again.
49.999999999... + 50.1111111111... = 100.111111111...
just sayin
I should’ve watched this channel more. This is straight up just quantum mechanics but in a really pedagogically succinct format
view 208 and i feel bad for calling this chick bo burnham because i kinda like her. but she still looks like bo yo
aha mate i can totally see it
Uncanny resemblance. O.o
But what about those adorable legs ?
Why does she stand with her feet turned inwards so much? I really doubt she's that pigeon-toed and it must be deliberate :/ So annoying
you make me feel that i know math!!! :)
btw keep moving your hands like you do, i don't no why but it really calm me down when things are getting complicated and so i can get back on track, finish the video and learn sonething, almost like you are taking us to a step-by-step learning with your hands ^^
thanks a lot, great video about something that i thought i would never understand...
In the description of a quantum computer can we please stop using the bit as the starting point. What makes computers easy to grok is the fact that they are based in switches. This isn't an analogy, they are literally switches. And that each switch has an on and an off state. Now, with that as a starting point, can someone put forth a description of a. Quantum computer that explains the mechanism behind a qubit, and please do better than just saying spin. I know this is a math channel, but with a masters in computer science, I need to know something of the physicality of the device to follow the logic. And no one ever goes into the details of how the quantum machines work.
I second Matt's request for more details on the actual physicality of the devices, it may help to understand what's what.
Watch and Read this in the order I gave you:
en.wikipedia.org/wiki/Interferometry
en.wikipedia.org/wiki/Quantum_entanglement
en.wikipedia.org/wiki/Quadrature_amplitude_modulation
th-cam.com/video/7Rtqbygk7Qk/w-d-xo.html
th-cam.com/video/zcqZHYo7ONs/w-d-xo.html
en.wikipedia.org/wiki/Chirality_(physics)
I have allready concepted a logical circuit which is able to register time correlated bits.
In a classical computer, the data are conveyed via data paths from storage devices, through gates, and back to storage. So the gates are physically separate from the storage (although not far away). In a quantum computer, a state is in a storage device, and microwaves are directed at it that device cause it to perform a gate function on the state stored in it. So the same device functions as storage and gates.
Matthew, this is an excellent question. In a normal computer the switches are formed by MOS transistors. And these MOSTs act as controllable switches. With drawing a schematic out of MOSTs you can see e.g. how a more complex gate like NOT or AND is formed. It would be great to have such schematic for a quantum gate. But I think currently such qbit gates are not formed by such MOSTs, but by a kind of physical testbench so that physics acts as a quantum gates, or even as a cascade of it. Unfortunately in such testbench there are no MOS transistor switches, and you need temparatures close to few Kelvins.
th-cam.com/video/OWJCfOvochA/w-d-xo.html
I would love to see more about applications of these things. I know math doesn't necessarily do that and I understand the videos just fine, I would love to see more about the differences from general computers, for example. Like in the factorization example, compare the two methods? Just something to think about.
Otherwise neat vid, loving this channel so far~~
a little bit of nit picking: I dont expect that any non-german speaker can pronounce Schrödinger correctly; but for a good scientific standard you should at least write his name right, i.e., with an "ö" instead of an "o".
@PBS Infinite Series PLEEAAAASSEEEE make an album of the music. It's so cool, I would listen to it all day. My favourite part starts at 3:00.
Finally a video can help me understanding quantum computing!!!
Your videos are getting better! Loving the background music.
This is it. TH-cam now officially HAS CONTENT. Seriously, thank you for bringing such competence to this platform. This is great to watch.
As a very lay man, below average Id say in the math department, this is absolutely amazing! if we could actually make a quantum computer the difference would be something like before Alan Turing invented his Turing machine, and its aftermath! loving this stuff, thank you!.
Its very good lecture on Quantom Computing... Thanks a lot..!
Really good. Thanks Kelsey Houston-Edwards :)
i know this is hand wavy, but is alot less hand wavy that most explanations and still manages to bring the message home, so thanks
Definitely the best video I've seen on quantum computing, great job! Although, I would have mentioned that it is interference that gives you the huge speed up.
Argh don't you dare throw theses evil physicist words around.
But seriously, isn't intererence and superposition the absolute same in this case? I'm curious
Ah, good question, but they are not the same. A superposition is when you have a state that is a combination of other states. This isn't some mathy trick though, the multiple states are really there and they can interact with each other. That interaction is interference. Think of foil from high school: (a+b)^2 = a^2 + 2ab + b^2, you can imagine that the 2ab term is an interference between a and b. Hope that helped.
Maybe I'm too much of a mathematician, but for me that sounds as if they are the same.
hmmm, ok consider this. Any state can be represented as a linear combination of eigenbasis vectors, such that the sum of the complex squares adds up to 1. Your state is in a superposition if it gives multiple eigenbasis vectors non-zero coefficients. Now if you want to know the probability of your state transitioning into some other superposition state, you compute an inner product. In the quantum mechanical formulation you will get extra terms in that inner product that you wouldn't get classically, those extra terms are the interference. Wikipedia has a nice quick description: en.wikipedia.org/wiki/Interference_(wave_propagation)#Quantum_interference
Ah ok that sounds interesting. How do these extre terms give you the speed up then?
Update to 27 January 2019 - there are quantum computers in production (albeit, coherence is questionable) - IBM, Rigetti, D-Wave (annealing), Google, AliBaba and others have working QC's
Speed and rythem is exciting. And you are outstanding.
Excellent explanation! if you have no control on what state a qubit(s) can be, how can you assign different probabilities to each state? In @3:30, was state |00> eliminated because it is the basic state, or is it purposefully given a zero probability? Another question, in @9:09 what do you exactly mean by 4 "steps" (runs?)? Thank you!
Such an amazing mathematical representation described in such a simple way!
Thanks , brilliant explanation, the best I have seen !
wait, so how do you take the value from the qubit if part of it is imaginary? or do you just take ignore the imaginary part and get the absolute value of the real part?