3 ms·

Uhhh no they aren’t, we have working quantum computers today

by mountainriver 4y ago

magila 4y ago
Depends on how generously you define "working". No one has yet implemented even a single logical qubit.
- nl 4y ago
  Well that is incorrect. Google's experimental quantum computer has been used to build logical qubits using up to 21 physical qubits. However "The team believes that mature quantum computers will need 1000 qubits to make each logical qubit – Sycamore currently has just 54 physical qubits." (A "mature quantum computers" is one where the fault tolerance is high enough for it to be generally useful outside experimental settings) https://www.newscientist.com/article/2283945-google-demonstrates-vital-step-towards-large-scale-quantum-computers/ https://www.newscientist.com/article/2283945-google-demonstr...
  - magila 4y ago
    A logical qubit is by definition one which has a low enough error rate to preform quantum computations. That article is misleadingly using the term "logical qubits" to refer to a grouping of physical qubits which merely attempts to reduce the error rate. The resulting rate is still too high to perform computations so it cannot, yet, be called a logical qubit in the accepted sense.
    - nl 4y ago
      Well "perform quantum computations" is being done by the Google quantum computer, so... they have done it?
      - pyinstallwoes 4y ago
        If you have to verify it on a classical computer then no.
        nl 4y ago
        Good thing then that you don't! Eg: https://scottaaronson.blog/?p=5122 https://scottaaronson.blog/?p=5122
        pyinstallwoes 4y ago
        “A somewhat similar story can be traced back to the 13th century when Nasreddin Hodja made a proposal to teach his donkey to read and obtained a 10-year grant from the local Sultan. For his first report he put breadcrumbs between the pages of a big book, and demonstrated the donkey turning the pages with his hoofs. This was a promising first step in the right direction. Nasreddin was a wise but simple man, so when asked by friends how he hopes to accomplish his goal, he answered: “My dear fellows, before ten years are up, either I will die or the Sultan will die. Or else, the donkey will die.” Had he the modern degree of sophistication, he could say, first, that there is no theorem forbidding donkeys to read. And, since this does not contradict any known fundamental principles, the failure to achieve this goal would reveal new laws of Nature. So, it is a win-win strategy: either the donkey learns to read, or new laws will be discovered.”
abrichr 4y ago
From https://www.technologyreview.com/2022/03/28/1048355/quantum-computing-has-a-hype-problem/ https://www.technologyreview.com/2022/03/28/1048355/quantum-... : > The qubit systems we have today are a tremendous scientific achievement, but they take us no closer to having a quantum computer that can solve a problem that anybody cares about. -- Sankar Das Sarma, Distinguished University Professor, Condensed Matter Theory Center, Univ. of Maryland From https://www.linkedin.com/pulse/quantum-computing-hype-bad-science-victor-galitski-1c/ https://www.linkedin.com/pulse/quantum-computing-hype-bad-sc... : > Crazy headlines abound: "quantum computing will change life as we know it," "quantum computing will solve global warming," "Quantum computing will revolutionize science and industry," etc etc. These statements are not based on any research or reality at all, they are not even wishful thinking. The number of known quantum algorithms, which promise advantage over classical computation, is just a few (and none of them will "solve global warming" for sure). More importantly, exactly zero such algorithms have been demonstrated in practice so far and the gap between what’s needed to realize them and the currently available hardware is huge, and it's not just a question of numbers. There are qualitative challenges with scaling up, which will likely take decades to resolve (if ever). -- Victor Galitski, Professor, Joint Quantum Institute, Univ. of Maryland
- bowsamic 4y ago
  What has that got to do with the comment you’re replying to?
- nl 4y ago
  This can be true, and the part quoted by the OP ("Flash forward to today, and the race is on to build fault-tolerant quantum computers and discover new algorithms to apply them in useful ways.") can also be true. The reason we don't have "a quantum computer that can solve a problem that anybody cares about" is because of that lack of fault tolerance, not because we don't have some experimental quantum computers that work in laboratory tests.
pyinstallwoes 4y ago
No we don't. There exists no physical working quantum computer today. There never has been a working physical quantum computer. There exists a "theoretical model that is simulated on classical computers" which is not a physical working quantum computer. https://scottlocklin.wordpress.com/2019/01/15/quantum-computing-as-a-field-is-obvious-bullshit/ https://scottlocklin.wordpress.com/2019/01/15/quantum-comput... I wish it weren't vaporware, truly.
- bowsamic 4y ago
  https://www.nature.com/articles/s41586-022-04725-x https://www.nature.com/articles/s41586-022-04725-x > Quantum computational advantage with a programmable photonic processor There is a programmable photonic computer that has an advantage over classical computers
  - pyinstallwoes 4y ago
    Oh, where can I buy one? See it in use at least, physically?
- nl 4y ago
  I read this post when it came out, nodded to myself and assumed it was correct because there seemed to have been no progress in quantum computing in my lifetime. Turns out he is wrong: https://www.nature.com/articles/d41586-019-03213-z https://www.nature.com/articles/d41586-019-03213-z I'd invite you to read the blog of that other HN favorite (Scott Aaronson) on the topic: For me, though, the broader point is that neither party here—certainly not IBM—denies that the top-supercomputers-on-the-planet-level difficulty of classically simulating Google’s 53-qubit programmable chip really is coming from the exponential character of the quantum states in that chip, and nothing else. https://scottaaronson.blog/?p=4372 https://scottaaronson.blog/?p=4372 And later when Jianwei Pan and Chao-Yang Lu, got BosonSampling working on a quantum computer: While directly verifying the results of n-photon BosonSampling takes ~2n time for any known classical algorithm, I said, surely it should be possible with existing computers to go up to n=40 or n=50? A couple weeks later, the authors responded, saying that they’d now verified their results up to n=40, but it burned $400,000 worth of supercomputer time so they decided to stop there. This was by far the most expensive referee report I ever wrote! https://scottaaronson.blog/?p=5122 https://scottaaronson.blog/?p=5122

Uhhh no they aren’t, we have working quantum computers today

magila 4y ago

Depends on how generously you define "working". No one has yet implemented even a single logical qubit.

nl 4y ago
Well that is incorrect. Google's experimental quantum computer has been used to build logical qubits using up to 21 physical qubits. However "The team believes that mature quantum computers will need 1000 qubits to make each logical qubit – Sycamore currently has just 54 physical qubits." (A "mature quantum computers" is one where the fault tolerance is high enough for it to be generally useful outside experimental settings) https://www.newscientist.com/article/2283945-google-demonstrates-vital-step-towards-large-scale-quantum-computers/ https://www.newscientist.com/article/2283945-google-demonstr...
- magila 4y ago
  A logical qubit is by definition one which has a low enough error rate to preform quantum computations. That article is misleadingly using the term "logical qubits" to refer to a grouping of physical qubits which merely attempts to reduce the error rate. The resulting rate is still too high to perform computations so it cannot, yet, be called a logical qubit in the accepted sense.
  - nl 4y ago
    Well "perform quantum computations" is being done by the Google quantum computer, so... they have done it?
    - pyinstallwoes 4y ago
      If you have to verify it on a classical computer then no.
      - nl 4y ago
        Good thing then that you don't! Eg: https://scottaaronson.blog/?p=5122 https://scottaaronson.blog/?p=5122
        pyinstallwoes 4y ago
        “A somewhat similar story can be traced back to the 13th century when Nasreddin Hodja made a proposal to teach his donkey to read and obtained a 10-year grant from the local Sultan. For his first report he put breadcrumbs between the pages of a big book, and demonstrated the donkey turning the pages with his hoofs. This was a promising first step in the right direction. Nasreddin was a wise but simple man, so when asked by friends how he hopes to accomplish his goal, he answered: “My dear fellows, before ten years are up, either I will die or the Sultan will die. Or else, the donkey will die.” Had he the modern degree of sophistication, he could say, first, that there is no theorem forbidding donkeys to read. And, since this does not contradict any known fundamental principles, the failure to achieve this goal would reveal new laws of Nature. So, it is a win-win strategy: either the donkey learns to read, or new laws will be discovered.”

abrichr 4y ago

From https://www.technologyreview.com/2022/03/28/1048355/quantum-computing-has-a-hype-problem/ https://www.technologyreview.com/2022/03/28/1048355/quantum-... : > The qubit systems we have today are a tremendous scientific achievement, but they take us no closer to having a quantum computer that can solve a problem that anybody cares about. -- Sankar Das Sarma, Distinguished University Professor, Condensed Matter Theory Center, Univ. of Maryland From https://www.linkedin.com/pulse/quantum-computing-hype-bad-science-victor-galitski-1c/ https://www.linkedin.com/pulse/quantum-computing-hype-bad-sc... : > Crazy headlines abound: "quantum computing will change life as we know it," "quantum computing will solve global warming," "Quantum computing will revolutionize science and industry," etc etc. These statements are not based on any research or reality at all, they are not even wishful thinking. The number of known quantum algorithms, which promise advantage over classical computation, is just a few (and none of them will "solve global warming" for sure). More importantly, exactly zero such algorithms have been demonstrated in practice so far and the gap between what’s needed to realize them and the currently available hardware is huge, and it's not just a question of numbers. There are qualitative challenges with scaling up, which will likely take decades to resolve (if ever). -- Victor Galitski, Professor, Joint Quantum Institute, Univ. of Maryland

bowsamic 4y ago
What has that got to do with the comment you’re replying to?
nl 4y ago
This can be true, and the part quoted by the OP ("Flash forward to today, and the race is on to build fault-tolerant quantum computers and discover new algorithms to apply them in useful ways.") can also be true. The reason we don't have "a quantum computer that can solve a problem that anybody cares about" is because of that lack of fault tolerance, not because we don't have some experimental quantum computers that work in laboratory tests.

pyinstallwoes 4y ago

No we don't. There exists no physical working quantum computer today. There never has been a working physical quantum computer. There exists a "theoretical model that is simulated on classical computers" which is not a physical working quantum computer. https://scottlocklin.wordpress.com/2019/01/15/quantum-computing-as-a-field-is-obvious-bullshit/ https://scottlocklin.wordpress.com/2019/01/15/quantum-comput... I wish it weren't vaporware, truly.

bowsamic 4y ago
https://www.nature.com/articles/s41586-022-04725-x https://www.nature.com/articles/s41586-022-04725-x > Quantum computational advantage with a programmable photonic processor There is a programmable photonic computer that has an advantage over classical computers
- pyinstallwoes 4y ago
  Oh, where can I buy one? See it in use at least, physically?
nl 4y ago
I read this post when it came out, nodded to myself and assumed it was correct because there seemed to have been no progress in quantum computing in my lifetime. Turns out he is wrong: https://www.nature.com/articles/d41586-019-03213-z https://www.nature.com/articles/d41586-019-03213-z I'd invite you to read the blog of that other HN favorite (Scott Aaronson) on the topic: For me, though, the broader point is that neither party here—certainly not IBM—denies that the top-supercomputers-on-the-planet-level difficulty of classically simulating Google’s 53-qubit programmable chip really is coming from the exponential character of the quantum states in that chip, and nothing else. https://scottaaronson.blog/?p=4372 https://scottaaronson.blog/?p=4372 And later when Jianwei Pan and Chao-Yang Lu, got BosonSampling working on a quantum computer: While directly verifying the results of n-photon BosonSampling takes ~2n time for any known classical algorithm, I said, surely it should be possible with existing computers to go up to n=40 or n=50? A couple weeks later, the authors responded, saying that they’d now verified their results up to n=40, but it burned $400,000 worth of supercomputer time so they decided to stop there. This was by far the most expensive referee report I ever wrote! https://scottaaronson.blog/?p=5122 https://scottaaronson.blog/?p=5122