8 ms·

Quantum Supersampling [video]

86 points by csl 10y ago

billconan 10y ago
This is very interesting, but I don't understand many things he said. is there a good introductory material for writing code for quantum computers and how quantum computers work? also is there a way to evaluate the performance boost with the simulator?
- krastanov 10y ago
  "Writing code for quantum computers" is not a great way to phrase it. Most day-to-day code you would write (a.k.a. business logic) will be something you still write for a classical computer. The quantum part would be black-box routines you call from a library that knows how to communicate with the special-purpose quantum hardware. It will be really good at solving problems "in between P and NP", not at doing anything useful for problems that are known to be in P. But I guess you were specifically interested in how to write those black box library routines that work on the (currently imaginary) quantum hardware you attached to your classical computer. There are two sides to this question: 1) You are interested in the physical system (compared to having interest in electronics in the case of classical computers). Then you have to learn the physics - what wavelength of laser you shine at your ion trap; what microwave signal you send to your superconducting cavity; how to focus your laser on the NV center in your diamond crystal, etc. Regrettably, I do not have better resource for this beyond just looking at review articles in Science and Nature (it is a very young and very active research area). You will need to learn the basic physics before doing that. This book [1] is the canonical resource for that field. 2) You are interested in the computer science (compared to studying Turing Machines and designing algorithms in the case of classical computers). For this I would point to Scott Aaronson's blog, his MIT lecture notes, and his books (and papers that he has aimed at the general public). [1]: http://www.cambridge.org/us/academic/subjects/physics/quantum-physics-quantum-information-and-quantum-computation/quantum-computation-and-quantum-information-10th-anniversary-edition http://www.cambridge.org/us/academic/subjects/physics/quantu... P.S. My points is, quantum computers are special purpose add-ons that solve very specific problems more efficiently than classical computers. For all classically easy problems (all problems in P) solving them on a classical computer will be faster, simply because building a classical computer is so much easier.
  - kirrent 10y ago
    To add to the above, if you are interested in (2) then most of the content of Aaronson's book 'Quantum Computing since Democritus' is on his website as lecture notes for an old class.
Strilanc 10y ago
This is a great talk. Like, I am going to be linking people to this for years. It mentions the basics, goes over an example use, and just generally has the perfect amount of "this could be cool". The one thing that bothered me, in the whole talk, is when he said that a 10-qubit circuit was beyond anything we could run right now. Simulators like Liquid [1] or even my browser-drag-and-drop toy Quirk [2] would easily run that circuit. In hindsight it's obvious that he meant on an actual quantum computer. 1: http://stationq.github.io/Liquid/ http://stationq.github.io/Liquid/ 2: http://algorithmicassertions.com/quirk http://algorithmicassertions.com/quirk
- krastanov 10y ago
  You probably already know that, but to clarify for other readers: Sure, 10 qubits happen to be doable on an classical computer, but the classical resource requirements for simulating quantum bits grow exponentially, so 40 qubits is about where even super computing clusters stop being useful and 100 qubits is beyond the capabilities of any classical computer you can fit on Earth.
  - matt42 10y ago
    I do not know anything in quantum computing but I read that D-Wave already reached 1000 qubits. Does it mean that their computer is already more powerful that any classical super computer ? http://www.dwavesys.com/press-releases/d-wave-systems-breaks-1000-qubit-quantum-computing-barrier http://www.dwavesys.com/press-releases/d-wave-systems-breaks...
    - Strilanc 10y ago
      It's not the same kind of quantum computer. D-Wave makes an annealer. They also have a history of making grandiose claims. I think getting to fifty proper qubits will be a much bigger deal than D-Wave getting to even ten thousand "qubits". But I suppose time will tell.
      - matt42 10y ago
sabujp 10y ago
This is awesome, I think I learned more about how QC works in this one talk than in everything I've seen and read up till now. What the gates actually are, what they do, and their relation to real bits and qbits
- alanbernstein 10y ago
  Hmm, I've tried and failed to understand QC a few times... I wonder if you could help me out here? What is supposed to be interesting about the result at 15:15? As far as I can tell, the shader contains all the information that is presented as the output here, so it doesn't seem impressive. But he says "our calculation produced the complete answer perfectly with zero noise" as if this is a serious accomplishment? I don't get it.
  - justifier 10y ago
    15:15 is interesting because using these shaders the researcher is able to illustrate the pixel pattern as it presents itself in terms of quantum phase differences and yes, you are right, in terms of relying solely on the simulation, this is hardly a 'serious accomplishment' because it relies on many classical computations to simulate but rather it is the shaders and their use that are the accomplishment the simulation is only a test bed to investigate the practicality of these shaders before placing them into a real quantum computer since working directly with quantum computers currently is both difficult and limiting you are better off with a computation heavy simulation to try out ideas to determine which ones have the greatest potential for successful results imagine prototyping on a device that needs to remain at 17millikelvin for instance, the author states it took some time before realising an inverted fourier transform was necessary to achieve these results, even noting almost giving up on the whole thing as a result of the constant failings while using the original idea of a forward fourier transform could such a revelation had been made using the actual quantum hardware? sure.. maybe, but the probability, ;p, is much much lower with the quantum computer you can think of the parallel computations in terms of a single classical computation so the computation heavy simulation shows that "our calculation produced the complete answer perfectly with zero noise" which is encouraging that if placed into a real quantum computer, as is shown later in the video, we can get zero noise results with essentially a single computation when placed into the real quantum computer the results still retain some noise due the limitations of current real quantum computers because they had to detrimentally limit their qubit use.. further exemplifying the importance of the simulator but given a quantum computer that can perform using the same number of qubits as the simulation these shaders should give zero noise results which would be a serious accomplishment .. is there a word for 'theoretically based on simulation'? simulationally theoretic? ;p
justifier 10y ago
18:17 is when it gets really good i think referring to it as a lookup table is self confounding the whole thing still regretfully relies on the random periodicity is the way to go but periodicity in place of the look up table i was stunned to see the graph at 19:53 to come by that graph through such a probabilistic method is validating those etched silicon photonic quantum gates shown following 23:14 are awesome the variable temperature controlled index of refraction phase operation reminded me of a previous link using optics to solve np-complete problems(o) and someone compared it to a sleep sort when he put up the results at 22:14 comparing with monte carlo i wondered what the time difference was for each calculated result i understand that energy requirements for the kind of state control necessary, like the low temperatures, the 2 degree kelvin quoted at 26:53, for single infared photon detection, make these physical quantum computers impractical when compared to classical computations like the monte carlo example.. he also talks a bit about decoherence issues as an unfortunate race saying 'so long to finish the program' how long is so long? though the clear consistency between the classical and physical quantum computer results is definitely more than 'almost interesting' i do wonder about what time was spent to get each result.. the goal is to optimise for speed, right? the simulator(i) is really cool (o) https://news.ycombinator.com/item?id=12362044 https://news.ycombinator.com/item?id=12362044 (i) http://qcengine.com/ http://qcengine.com/

86 points by csl 10y ago

This is very interesting, but I don't understand many things he said. is there a good introductory material for writing code for quantum computers and how quantum computers work? also is there a way to evaluate the performance boost with the simulator?

krastanov 10y ago
"Writing code for quantum computers" is not a great way to phrase it. Most day-to-day code you would write (a.k.a. business logic) will be something you still write for a classical computer. The quantum part would be black-box routines you call from a library that knows how to communicate with the special-purpose quantum hardware. It will be really good at solving problems "in between P and NP", not at doing anything useful for problems that are known to be in P. But I guess you were specifically interested in how to write those black box library routines that work on the (currently imaginary) quantum hardware you attached to your classical computer. There are two sides to this question: 1) You are interested in the physical system (compared to having interest in electronics in the case of classical computers). Then you have to learn the physics - what wavelength of laser you shine at your ion trap; what microwave signal you send to your superconducting cavity; how to focus your laser on the NV center in your diamond crystal, etc. Regrettably, I do not have better resource for this beyond just looking at review articles in Science and Nature (it is a very young and very active research area). You will need to learn the basic physics before doing that. This book [1] is the canonical resource for that field. 2) You are interested in the computer science (compared to studying Turing Machines and designing algorithms in the case of classical computers). For this I would point to Scott Aaronson's blog, his MIT lecture notes, and his books (and papers that he has aimed at the general public). [1]: http://www.cambridge.org/us/academic/subjects/physics/quantum-physics-quantum-information-and-quantum-computation/quantum-computation-and-quantum-information-10th-anniversary-edition http://www.cambridge.org/us/academic/subjects/physics/quantu... P.S. My points is, quantum computers are special purpose add-ons that solve very specific problems more efficiently than classical computers. For all classically easy problems (all problems in P) solving them on a classical computer will be faster, simply because building a classical computer is so much easier.
- kirrent 10y ago
  To add to the above, if you are interested in (2) then most of the content of Aaronson's book 'Quantum Computing since Democritus' is on his website as lecture notes for an old class.

Strilanc 10y ago

This is a great talk. Like, I am going to be linking people to this for years. It mentions the basics, goes over an example use, and just generally has the perfect amount of "this could be cool". The one thing that bothered me, in the whole talk, is when he said that a 10-qubit circuit was beyond anything we could run right now. Simulators like Liquid [1] or even my browser-drag-and-drop toy Quirk [2] would easily run that circuit. In hindsight it's obvious that he meant on an actual quantum computer. 1: http://stationq.github.io/Liquid/ http://stationq.github.io/Liquid/ 2: http://algorithmicassertions.com/quirk http://algorithmicassertions.com/quirk

krastanov 10y ago
You probably already know that, but to clarify for other readers: Sure, 10 qubits happen to be doable on an classical computer, but the classical resource requirements for simulating quantum bits grow exponentially, so 40 qubits is about where even super computing clusters stop being useful and 100 qubits is beyond the capabilities of any classical computer you can fit on Earth.
- matt42 10y ago
  I do not know anything in quantum computing but I read that D-Wave already reached 1000 qubits. Does it mean that their computer is already more powerful that any classical super computer ? http://www.dwavesys.com/press-releases/d-wave-systems-breaks-1000-qubit-quantum-computing-barrier http://www.dwavesys.com/press-releases/d-wave-systems-breaks...
  - Strilanc 10y ago
    It's not the same kind of quantum computer. D-Wave makes an annealer. They also have a history of making grandiose claims. I think getting to fifty proper qubits will be a much bigger deal than D-Wave getting to even ten thousand "qubits". But I suppose time will tell.
    - matt42 10y ago

sabujp 10y ago

This is awesome, I think I learned more about how QC works in this one talk than in everything I've seen and read up till now. What the gates actually are, what they do, and their relation to real bits and qbits

alanbernstein 10y ago
Hmm, I've tried and failed to understand QC a few times... I wonder if you could help me out here? What is supposed to be interesting about the result at 15:15? As far as I can tell, the shader contains all the information that is presented as the output here, so it doesn't seem impressive. But he says "our calculation produced the complete answer perfectly with zero noise" as if this is a serious accomplishment? I don't get it.
- justifier 10y ago
  15:15 is interesting because using these shaders the researcher is able to illustrate the pixel pattern as it presents itself in terms of quantum phase differences and yes, you are right, in terms of relying solely on the simulation, this is hardly a 'serious accomplishment' because it relies on many classical computations to simulate but rather it is the shaders and their use that are the accomplishment the simulation is only a test bed to investigate the practicality of these shaders before placing them into a real quantum computer since working directly with quantum computers currently is both difficult and limiting you are better off with a computation heavy simulation to try out ideas to determine which ones have the greatest potential for successful results imagine prototyping on a device that needs to remain at 17millikelvin for instance, the author states it took some time before realising an inverted fourier transform was necessary to achieve these results, even noting almost giving up on the whole thing as a result of the constant failings while using the original idea of a forward fourier transform could such a revelation had been made using the actual quantum hardware? sure.. maybe, but the probability, ;p, is much much lower with the quantum computer you can think of the parallel computations in terms of a single classical computation so the computation heavy simulation shows that "our calculation produced the complete answer perfectly with zero noise" which is encouraging that if placed into a real quantum computer, as is shown later in the video, we can get zero noise results with essentially a single computation when placed into the real quantum computer the results still retain some noise due the limitations of current real quantum computers because they had to detrimentally limit their qubit use.. further exemplifying the importance of the simulator but given a quantum computer that can perform using the same number of qubits as the simulation these shaders should give zero noise results which would be a serious accomplishment .. is there a word for 'theoretically based on simulation'? simulationally theoretic? ;p

justifier 10y ago

18:17 is when it gets really good i think referring to it as a lookup table is self confounding the whole thing still regretfully relies on the random periodicity is the way to go but periodicity in place of the look up table i was stunned to see the graph at 19:53 to come by that graph through such a probabilistic method is validating those etched silicon photonic quantum gates shown following 23:14 are awesome the variable temperature controlled index of refraction phase operation reminded me of a previous link using optics to solve np-complete problems(o) and someone compared it to a sleep sort when he put up the results at 22:14 comparing with monte carlo i wondered what the time difference was for each calculated result i understand that energy requirements for the kind of state control necessary, like the low temperatures, the 2 degree kelvin quoted at 26:53, for single infared photon detection, make these physical quantum computers impractical when compared to classical computations like the monte carlo example.. he also talks a bit about decoherence issues as an unfortunate race saying 'so long to finish the program' how long is so long? though the clear consistency between the classical and physical quantum computer results is definitely more than 'almost interesting' i do wonder about what time was spent to get each result.. the goal is to optimise for speed, right? the simulator(i) is really cool (o) https://news.ycombinator.com/item?id=12362044 https://news.ycombinator.com/item?id=12362044 (i) http://qcengine.com/ http://qcengine.com/