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VW Solves Quantum Chemistry Problems on a D-Wave Machine

spectrum.ieee.org

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Re: VW Solves Quantum Chemistry Problems on a D-Wave Machine

#21

Post by twtw »

jf- wrote: post #8
twtw wrote: post #5

... and couldn't get the correct answers for LiH. Interesting that the article didn't mention this. From the paper: > For lithium hydride, LiH, we were not able to reproduce closely the ground state energy with the currently available hardware. When accounting for 3 orbitals and using a scaling factor of r = 4, we already had to use 1558 qubits, which is a large fraction of available qubits. To summarize: the investi…

Presumably because that’s just a matter of scale. The calculation didn’t turn out wrong, the machine just isn’t powerful enough to calculate it. All of this work is proof of concept for more powerful devices down the road, the point isn’t that it’s better than a classical computer right now.

Right, and the paper itself is very upfront about that. I don't have any objection to the research, which is likely very valuable, but I do find it strange that the article claims they solved two problems without mentioning that only one of the solutions was correct.

It would be great if the article said they solved one and made good progress on techniques for the second that will likely work on next generation hardware, but the article didn't say that. I don't see how it being a matter of scale makes this acceptable. It's like the U.S. national labs unveiling the world's first exaflop supercomputer, with a footnote indicating that in fact the computer is only 100 petaflops at the moment.

Re: VW Solves Quantum Chemistry Problems on a D-Wave Machine

#22

Post by stochastic_monk »

FeepingCreature wrote: post #16
williamscales wrote: post #11

Earlier quoted context omitted.

Is there any evidence it will ever be better than a classical computer?

For the record, the concept is called Quantum Supremacy [1]. So far, there is no demonstration of quantum supremacy, but it seems like it may just be a matter of time. [1] https://en.wikipedia.org/wiki/Quantum_supremacy

It’s related, but quantum supremacy is about asymptotic speedups rather than actual speed differences.

Additionally, it’s worth keeping in mind that D-Wave machines aren’t true quantum computers in the sense that they can’t perform Grover’s or Shor’s algorithms.

Re: VW Solves Quantum Chemistry Problems on a D-Wave Machine

#23

Post by B1FF_PSUVM »

pas wrote: post #17
AlexCoventry wrote: post #15

What's the business motivation of this research, for VW?

Batteries? Fuel efficiency? Better catalytic emission filter?

Better cheating?

Although they're already pretty successful at that, the dieselgate thing cost them some money, but none of the executives in charge of the fraud is in jail or financially punished.

["How VW Paid $25 Billion for 'Dieselgate' – and Got Off Easy" - https://en.wikipedia.org/wiki/Volkswagen_emissions_scandal ]

Re: VW Solves Quantum Chemistry Problems on a D-Wave Machine

#24

Post by throwawaymath »

FeepingCreature wrote: post #16
williamscales wrote: post #11

Earlier quoted context omitted.

Is there any evidence it will ever be better than a classical computer?

For the record, the concept is called Quantum Supremacy [1]. So far, there is no demonstration of quantum supremacy, but it seems like it may just be a matter of time. [1] https://en.wikipedia.org/wiki/Quantum_supremacy

Quantum supremacy is not merely about quantum computers performing tasks better than classical computers. It's about quantum computers achieving a superpolynomial speedup over classical computers, such that classical computers can't feasibly perform the task in a reasonable amount of time for all inputs.

That's an important distinction because it's significantly more difficult to achieve a fundamental asymptotic improvement instead of an iterative speedup for the same factor. If a quantum computer completes a task with complexity O(2n) that a classical computer requires O(10n) to complete, you don't have quantum supremacy. If your quantum computer can accomplish a task in O(2n) that your classical computer needs O(2^n) to perform, you've got supremacy.

Given that nuance, I wouldn't say it may be a matter of time before we demonstrate quantum supremacy. There is still an undercurrent of skepticism in the research community.

Re: VW Solves Quantum Chemistry Problems on a D-Wave Machine

#25

Post by blattimwind »

B1FF_PSUVM wrote: post #23
pas wrote: post #17

Earlier quoted context omitted.

Batteries? Fuel efficiency? Better catalytic emission filter?

Better cheating? Although they're already pretty successful at that, the dieselgate thing cost them some money, but none of the executives in charge of the fraud is in jail or financially punished. ["How VW Paid $25 Billion for 'Dieselgate' – and Got Off Easy" - https://en.wikipedia.org/wiki/Volkswagen_emissions_scandal ]

https://en.wikipedia.org/wiki/Defeat_device#Timeline

https://en.wikipedia.org/wiki/Diesel_emissions_scandal

Re: VW Solves Quantum Chemistry Problems on a D-Wave Machine

#27

Post by Dylan16807 »

jackfraser wrote: post #19
crb002 wrote: post #9

Curious to see Aaronson's criticism.

Aaronson is unfortunately in a sunk-cost position when it comes to D-Wave - he's been so against them for so long that even if they start to produce good results his bias is going to make it difficult for him to fairly evaluate them, especially if it means reaching different conclusions about their past work than he did previously. Probably better to look to other commentators on this one, at least until he has enoug…

Your first paragraph is fine.

But your second says "process the situation and come around to it" as if they've already proven anything.

Nobody has ever seriously claimed that the machine can't calculate things. Proof of it doing a calculation doesn't change the status quo.

Re: VW Solves Quantum Chemistry Problems on a D-Wave Machine

#28

Post by tbabej »

zaroth wrote: post #3

I appreciated the rudimentary presentation of the capabilities and limitations of the machine and calling out the connectivity of the qubits versus a universal quantum machine which would have full connectivity between all the bits. I’d be curious is there a simple formula for calculating the “effective universal qubits” of the D-Wave? 2,048 indeed sounds like a lot of qubits based on my extremely limited knowledge o…

It's important to note here that the current gate-based quantum processors also suffer from the connectivity problems. It's not just annealers suffering.

In those architectures, the limited connectivity enforces usage of SWAP gates, which increases the circuit depth.

Circuit depth, with imperfect qubits and gates, is currently the limiting factor - we don't have practical error-correction for the chips of today's size. Hence one can only perform a certain number of operations before his computation decoheres and becomes useless.

Re: VW Solves Quantum Chemistry Problems on a D-Wave Machine

#30

Post by _Nat_ »

crb002 wrote: post #9

Curious to see Aaronson's criticism.

I kinda doubt anyone's going to really criticize this one.

I mean, the controversy about D-Wave (if I recall correctly) was largely related to claims about it having achieved [quantum advantage over classical computing methods](https://en.wikipedia.org/wiki/Quantum_supremacy), along with misunderstandings about what kind of "quantum computer" it is.

However, it's generally accepted that D-Wave is a working computer that uses quantum models; that fact's uncontroversial.

In this paper, they reported using that uncontroversial ability to perform optimization problems to optimize some physics problems. And it worked basically as-expected.

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