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Пишет Journal de Chaource (![[info]](http://lj.rossia.org/img/syndicated.gif){kind=small} lj_chaource)@ 2018-11-24 22:48:00 |
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Computer science professors' views on quantum computing
https://quantumcomputing.stackexchange.c
A very informative discussion thread about promises and doubts of quantum computing. I'm starting to have hope again, actually. The reason I am starting to have hope is that IBM, Google, and Intel are working on actual QC devices, not of the D-Wave kind (which are not general QCs), but of the real kind, and they can already create devices with 50-70 qubits that "sort of half-work". I have no faith at all in the academic researchers, - and the quotations from the professors below confirm my skepticism, - but I do have faith in engineers working for a corporation, because they have to deliver results and not just publications and grant reports.
PS
My objection to QCs is that it will be impossible to keep the decoherence of qubits small while at the same the qubits must be all highly interconnected and coupled to a large classical "levers" that we use to control the QC. Scott Aaronson's article linked below does not answer this objection at all, sadly. This is objection 9 in his post, but when discussing this objection, he avoids answering and changes the topic.
Quotes:
Is quantum computing just pie in the sky?
1.
So far it is looking this way. We have been reaching for this pie aggressively over the last three decades but with not much success. We do have quantum computers now, but they are not the pie we wanted, which is a quantum computer that can actually solve a problem faster or with better energetic efficiency than a classical computer.
2.
I've been working on the theory of quantum computers for about 15 years. I've seen nothing convincing to say that they won't work. Of course, the only real proof that they can work is to make one. It's happening now. However, what a quantum computer will do and why we want it does not match up with the public perception.
...
Quantum computers are not pushing the theory into an untested regime where we might hope there are unexpected results ... quantum mechanics is already applied to condensed matter systems consisting of far more constituents than we're talking about qubits in a near-term quantum computer. It's just that we need an unprecedented level of control over them. A few people think they have arguments for why a quantum computer won't work, but I've not found anything particularly convincing in the arguments that I've read.
Is it all just jam-tomorrow woo peddled by quantum quacks to a gullible public? If not, why not?
1.
Much of it is, unfortunately.
...Many professors don't find it easy or "natural" to write well-received grant proposals, but they need funding to keep their job, and to make sure their PhD students aren't starved of experiencing scientific conferences and having access to the software they need.
When a professor becomes:
- desperate for funding, or
- caught up with other problems in life, such as having to take care of a child with cancer, or
- aware that they won't make huge scientific discoveries like some scientists did 100s of years ago,
life becomes more about surviving, keeping a happy family, and doing what they enjoy rather than making a better world for their grandchildren's grandchildren. As a professor, I can tell you that many of my colleagues are not as "noble" as the public often perceives scientists to be.
I know around 1000 people with funding to work in quantum computing, and not a single one seems to have ill intentions to fool a "gullible public" in some sinister way. Most of us just apply for grants available through our universities or through our governments, and we don't intend to exaggerate the importance of our work any more than other scientists competing for the same money (we have to compete with molecular physicists pretending their work is important for fixing climate change just because the molecule they're working on is in our atmosphere, or biophysicists pretending their work might cure cancer just because they're working on a molecule that's prominent in the body).
2.
Theoretically, there's no convincing argument (yet) as to why quantum computers aren't practically realizable. But, do check out: How Quantum Computers Fail: Quantum Codes, Correlations in Physical Systems, and Noise Accumulation - Gil Kalai (PDF alert!) and the related blog post by Scott Aaronson. If you want to dig into the history of why Aaronson thinks Kalai's claims are flawed, consider reading and following the links in the blog article. Also, see James Wotton's answer to the related QCSE post: Is Gil Kalai's argument against topological quantum computers sound?
However, yes, of course, there are engineering problems.
...
Progress:
Around a decade and a half, ago the decoherence time for the so-called "quantum computers" were lesser than 1 nanosecond. Now, the IBM Quantum Experience 16 qubit version which you can access online has a decoherence time 100 μs (see: Demonstration of Envariance and Parity Learning on the IBM 16 Qubit Processor (Davide Ferrari & Michele Amoretti, 2018)). The decoherence time of 100μs is sufficient to run simple quantum algorithms already! You can check it out yourself on the 5 qubit and 16 qubit quantum computers which have been made accessible online by IBM. I think Google has been able to achieve even better decoherence times with their superconducting chips (having an equivalent number of qubits).
There has been a lot of improvement in the area of quantum error correction in the past decade (requiring a much lesser number of total qubits). See Quantum Error Correction for Quantum Memories (Terhal, 2015) for a brief review.
...
Conclusion:
Whether we will ever have efficient quantum computers which can visibly outperform classical computers in certain areas, is something which only time will say. However, looking at the considerable progress we have been making, it probably wouldn't be too wrong to say that in a couple of decades we should have sufficiently powerful quantum computers. On the theoretical side though, we don't yet know if classical algorithms (can) exist which will match quantum algorithms in terms of time complexity.
After a bit of searching, I found a very nice article which outlines almost all of Scott Aaronson's counter-arguments against the quantum computing skepticism.
Is it all hype and hot air?
1.
A lot of the "hype" around quantum computing comes from the media. Journalists have twisted the contents of my papers to make eye-catching headlines which will get more clicks on their ads, and their bosses give them pressure to do this or they'll lose their job to the other intern that doesn't care as much about being honest.
Some of the hype does come from scientists themselves, many who truly believe quantum computing will be revolutionary because their PhD supervisor didn't have a great education ..., or perhaps in rare cases there is hype from people desperate for funding, but not much for reasons other than these.
I do believe the public should invest a bit in quantum computing, as they do for lots of other areas of research which have no guaranteed positive outcome. The hype is often exaggerated by journalists, ignorant scientists, or non-ignorant scientists who think they need it for survival. There is also unfairly harsh criticism from journalists and funding agencies.
2.
There is a lot of hype surrounding quantum computers. I would say that this comes from two main sources:
- the popular representation of quantum computing in the mainstream media and popular culture (e.g. science fiction books). Ask anybody actively working on quantum computation, I think they will all agree it's poorly represented, giving the impression that it's a universal solution that will make everything run quicker, which is, at least for now, not the case. There has been some jam-tomorrow woo peddled to a gullible public, but that's more through a "lost in translation" attempt to over-simplify what's going on, mostly by non-specialist intermediaries.
- researchers themselves. For the past 20(ish) years, people have been promising that quantum computing is just over the horizon, and its never quite materialized. It's quite reasonable that observers get sick of it at that point. However, my perspective from being within the field is that many people claiming to be working towards quantum computers haven't been. As funding bodies have got progressively more demanding with the "why" for research, and ensuring "impact", quantum computing has become the go-to for many experimentalists, even if they aren't really interested in doing anything for a quantum computer. If there's been some way that they can twist what they're doing so that it sounds relevant to quantum computing, they've tended to do it. It doesn't mean that quantum computing can't be done, it just hasn't been as much of a focus as has been implied. Take, at a slightly different level, the explosion of quantum information theory. So few theorists within that have actively worked on the theory of quantum computers and how to make them work (that's not to say they've not been doing interesting things).
...the parties most responsible for excitement about quantum computation are certain kinds of magazines and special-interest websites, which as sources of information are like market-square waffle vendors: they trade very much on sweet vaporous aromas rather than something with substance and bite. The attention-seeking advertising industry, rather than academia, are the main reason why there are such puffed-up expectations of quantum computation. They don't even care about quantum computation in principle: it is one of several magical incantations with which to amaze the crowd, to evoke dreams of pie in the sky, and in the meantime make money from some other company for the mere possibility that an ad was seen for half a second. That industry is very much in the business of selling airborne pastry, both to their clients and to their audience. But does that mean that the world is owed flying fig rolls by those who are actually working on quantum technologies? It's hard enough to accomplish the things which we think might be possible to accomplish — which are more modest, but still worthwhile.
Among my academic peers (theoretical computer scientists and theoretical physicists), the blatant misinformation about quantum computation among the public is a source of significant frustration. Most of us believe that it will be possible to build a quantum computer, and most of those who do also believe that it will have significant economic impacts. But none of us expect that it would turn the world upside-down in five to ten years, nor have we been expecting that for any of the past fifteen years that it started to become fashionable to say that we would have massive quantum computers "in five to ten years". I have always made it a point to say that I hope to see the impacts in my lifetime, and recent activity has made me hope to see it within twenty — but even then you won't be going to the store to buy one, any more than you go down to the store to buy a Cray supercomputer.
Nor do any of us expect that it will allow you to easily solve the Travelling Salesman Problem, or the like. Being able to analyse problems in quantum chemistry and quantum materials is the original, and in the short term still the best, prospective application of quantum computation, and it may be revolutionary there; and perhaps in the longer term we can provide robust and significant improvements in practise for optimisation problems. (D-Wave claims they can already do this in practise with their machines: the jury is still out among academics whether this claim is justified.)
https://quantumcomputing.stackexchange.c
A very informative discussion thread about promises and doubts of quantum computing. I'm starting to have hope again, actually. The reason I am starting to have hope is that IBM, Google, and Intel are working on actual QC devices, not of the D-Wave kind (which are not general QCs), but of the real kind, and they can already create devices with 50-70 qubits that "sort of half-work". I have no faith at all in the academic researchers, - and the quotations from the professors below confirm my skepticism, - but I do have faith in engineers working for a corporation, because they have to deliver results and not just publications and grant reports.
PS
My objection to QCs is that it will be impossible to keep the decoherence of qubits small while at the same the qubits must be all highly interconnected and coupled to a large classical "levers" that we use to control the QC. Scott Aaronson's article linked below does not answer this objection at all, sadly. This is objection 9 in his post, but when discussing this objection, he avoids answering and changes the topic.
Quotes:
Is quantum computing just pie in the sky?
1.
So far it is looking this way. We have been reaching for this pie aggressively over the last three decades but with not much success. We do have quantum computers now, but they are not the pie we wanted, which is a quantum computer that can actually solve a problem faster or with better energetic efficiency than a classical computer.
2.
I've been working on the theory of quantum computers for about 15 years. I've seen nothing convincing to say that they won't work. Of course, the only real proof that they can work is to make one. It's happening now. However, what a quantum computer will do and why we want it does not match up with the public perception.
...
Quantum computers are not pushing the theory into an untested regime where we might hope there are unexpected results ... quantum mechanics is already applied to condensed matter systems consisting of far more constituents than we're talking about qubits in a near-term quantum computer. It's just that we need an unprecedented level of control over them. A few people think they have arguments for why a quantum computer won't work, but I've not found anything particularly convincing in the arguments that I've read.
Is it all just jam-tomorrow woo peddled by quantum quacks to a gullible public? If not, why not?
1.
Much of it is, unfortunately.
...Many professors don't find it easy or "natural" to write well-received grant proposals, but they need funding to keep their job, and to make sure their PhD students aren't starved of experiencing scientific conferences and having access to the software they need.
When a professor becomes:
- desperate for funding, or
- caught up with other problems in life, such as having to take care of a child with cancer, or
- aware that they won't make huge scientific discoveries like some scientists did 100s of years ago,
life becomes more about surviving, keeping a happy family, and doing what they enjoy rather than making a better world for their grandchildren's grandchildren. As a professor, I can tell you that many of my colleagues are not as "noble" as the public often perceives scientists to be.
I know around 1000 people with funding to work in quantum computing, and not a single one seems to have ill intentions to fool a "gullible public" in some sinister way. Most of us just apply for grants available through our universities or through our governments, and we don't intend to exaggerate the importance of our work any more than other scientists competing for the same money (we have to compete with molecular physicists pretending their work is important for fixing climate change just because the molecule they're working on is in our atmosphere, or biophysicists pretending their work might cure cancer just because they're working on a molecule that's prominent in the body).
2.
Theoretically, there's no convincing argument (yet) as to why quantum computers aren't practically realizable. But, do check out: How Quantum Computers Fail: Quantum Codes, Correlations in Physical Systems, and Noise Accumulation - Gil Kalai (PDF alert!) and the related blog post by Scott Aaronson. If you want to dig into the history of why Aaronson thinks Kalai's claims are flawed, consider reading and following the links in the blog article. Also, see James Wotton's answer to the related QCSE post: Is Gil Kalai's argument against topological quantum computers sound?
However, yes, of course, there are engineering problems.
...
Progress:
Around a decade and a half, ago the decoherence time for the so-called "quantum computers" were lesser than 1 nanosecond. Now, the IBM Quantum Experience 16 qubit version which you can access online has a decoherence time 100 μs (see: Demonstration of Envariance and Parity Learning on the IBM 16 Qubit Processor (Davide Ferrari & Michele Amoretti, 2018)). The decoherence time of 100μs is sufficient to run simple quantum algorithms already! You can check it out yourself on the 5 qubit and 16 qubit quantum computers which have been made accessible online by IBM. I think Google has been able to achieve even better decoherence times with their superconducting chips (having an equivalent number of qubits).
There has been a lot of improvement in the area of quantum error correction in the past decade (requiring a much lesser number of total qubits). See Quantum Error Correction for Quantum Memories (Terhal, 2015) for a brief review.
...
Conclusion:
Whether we will ever have efficient quantum computers which can visibly outperform classical computers in certain areas, is something which only time will say. However, looking at the considerable progress we have been making, it probably wouldn't be too wrong to say that in a couple of decades we should have sufficiently powerful quantum computers. On the theoretical side though, we don't yet know if classical algorithms (can) exist which will match quantum algorithms in terms of time complexity.
After a bit of searching, I found a very nice article which outlines almost all of Scott Aaronson's counter-arguments against the quantum computing skepticism.
Is it all hype and hot air?
1.
A lot of the "hype" around quantum computing comes from the media. Journalists have twisted the contents of my papers to make eye-catching headlines which will get more clicks on their ads, and their bosses give them pressure to do this or they'll lose their job to the other intern that doesn't care as much about being honest.
Some of the hype does come from scientists themselves, many who truly believe quantum computing will be revolutionary because their PhD supervisor didn't have a great education ..., or perhaps in rare cases there is hype from people desperate for funding, but not much for reasons other than these.
I do believe the public should invest a bit in quantum computing, as they do for lots of other areas of research which have no guaranteed positive outcome. The hype is often exaggerated by journalists, ignorant scientists, or non-ignorant scientists who think they need it for survival. There is also unfairly harsh criticism from journalists and funding agencies.
2.
There is a lot of hype surrounding quantum computers. I would say that this comes from two main sources:
- the popular representation of quantum computing in the mainstream media and popular culture (e.g. science fiction books). Ask anybody actively working on quantum computation, I think they will all agree it's poorly represented, giving the impression that it's a universal solution that will make everything run quicker, which is, at least for now, not the case. There has been some jam-tomorrow woo peddled to a gullible public, but that's more through a "lost in translation" attempt to over-simplify what's going on, mostly by non-specialist intermediaries.
- researchers themselves. For the past 20(ish) years, people have been promising that quantum computing is just over the horizon, and its never quite materialized. It's quite reasonable that observers get sick of it at that point. However, my perspective from being within the field is that many people claiming to be working towards quantum computers haven't been. As funding bodies have got progressively more demanding with the "why" for research, and ensuring "impact", quantum computing has become the go-to for many experimentalists, even if they aren't really interested in doing anything for a quantum computer. If there's been some way that they can twist what they're doing so that it sounds relevant to quantum computing, they've tended to do it. It doesn't mean that quantum computing can't be done, it just hasn't been as much of a focus as has been implied. Take, at a slightly different level, the explosion of quantum information theory. So few theorists within that have actively worked on the theory of quantum computers and how to make them work (that's not to say they've not been doing interesting things).
...the parties most responsible for excitement about quantum computation are certain kinds of magazines and special-interest websites, which as sources of information are like market-square waffle vendors: they trade very much on sweet vaporous aromas rather than something with substance and bite. The attention-seeking advertising industry, rather than academia, are the main reason why there are such puffed-up expectations of quantum computation. They don't even care about quantum computation in principle: it is one of several magical incantations with which to amaze the crowd, to evoke dreams of pie in the sky, and in the meantime make money from some other company for the mere possibility that an ad was seen for half a second. That industry is very much in the business of selling airborne pastry, both to their clients and to their audience. But does that mean that the world is owed flying fig rolls by those who are actually working on quantum technologies? It's hard enough to accomplish the things which we think might be possible to accomplish — which are more modest, but still worthwhile.
Among my academic peers (theoretical computer scientists and theoretical physicists), the blatant misinformation about quantum computation among the public is a source of significant frustration. Most of us believe that it will be possible to build a quantum computer, and most of those who do also believe that it will have significant economic impacts. But none of us expect that it would turn the world upside-down in five to ten years, nor have we been expecting that for any of the past fifteen years that it started to become fashionable to say that we would have massive quantum computers "in five to ten years". I have always made it a point to say that I hope to see the impacts in my lifetime, and recent activity has made me hope to see it within twenty — but even then you won't be going to the store to buy one, any more than you go down to the store to buy a Cray supercomputer.
Nor do any of us expect that it will allow you to easily solve the Travelling Salesman Problem, or the like. Being able to analyse problems in quantum chemistry and quantum materials is the original, and in the short term still the best, prospective application of quantum computation, and it may be revolutionary there; and perhaps in the longer term we can provide robust and significant improvements in practise for optimisation problems. (D-Wave claims they can already do this in practise with their machines: the jury is still out among academics whether this claim is justified.)
