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What You Shouldn't Know About Quantum Computers

arxiv.org

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Re: What You Shouldn't Know About Quantum Computers

#21

Post by bee_rider »

zeroonetwothree wrote: post #16
sampo wrote: post #7

> Researchers like Jaime Sevilla and Jess Riedel support this timeline, publishing a report in late 2020 that claimed a 90% confidence of RSA-2048 being factored before 2060. I am skeptical. 36 years is a long time, but in the past 10 years there hasn't been much progress: year 2001: factorization of 15 (IBM) year 2012: factorization of 21 (University of Bristol) year 2019: factorization of 35 attempt, failed (IBM) h…

It’s hard to make predictions, especially about the future.

When a prediction has a probability attached to it, it should be possible to check the math. In some sense it isn’t really a prediction about the future, so much as a statement about current information (which is not complete).

Or, possibly, they are using “90% confidence” colloquially as “pretty sure.” If so, that should probably be made more clear. He’s using the fact that the researchers agree as an argument from authority, which is doubly wrong if the apparent authorities here were just giving their hunches.

Re: What You Shouldn't Know About Quantum Computers

#23

Post by JanisErdmanis »

sebzim4500 wrote: post #9
sampo wrote: post #7

> Researchers like Jaime Sevilla and Jess Riedel support this timeline, publishing a report in late 2020 that claimed a 90% confidence of RSA-2048 being factored before 2060. I am skeptical. 36 years is a long time, but in the past 10 years there hasn't been much progress: year 2001: factorization of 15 (IBM) year 2012: factorization of 21 (University of Bristol) year 2019: factorization of 35 attempt, failed (IBM) h…

IIRC none of those uses of shor's algorithm were real (well maybe the 2019 one was, but that failed). There's a threshold you need to reach for quantum error correction to work and we are approaching it pretty steadily on a log scale.

Quantum error correction produces logical qubits that have smaller nonzero error rate. Thus it needs to be applied repeatedly to achieve a necessary error rate to produce meaningful results. For Shor algorithm the error rate needs to decrease exponentially with the number of qubits. Thus even though IBM has a hundred qubits QCs they still only have managed to use five qubits to factorize a number 21.

Re: What You Shouldn't Know About Quantum Computers

#24

Post by naasking »

> Researchers like Jaime Sevilla and Jess Riedel support this timeline, publishing a report in late 2020 that claimed a 90% confidence of RSA-2048 being factored before 2060.

Delusional, IMO. Without a proper understanding of how the non-linearity of the macroscopic world arises from the unitarity of QM, any scaling projections are wishful thinking. We just don't have a good enough understanding of the measurement problem and decoherence to make such projections.

Re: What You Shouldn't Know About Quantum Computers

#25

Post by renonce »

> For example, would quantum computers work by trying all possible answers in parallel? Sorry, no, that's too good to be true: Quantum computers work by choreographing a pattern of interference, where the contributions to the amplitude of each wrong answer cancel each other out, while the contributions to the right answer's amplitude reinforce each other. Only for special problems, as it turns out, do we know how to choreograph such an interference pattern to deliver a huge speedup over the best known classical algorithms. This, in turn, is why we don't expect quantum computers ever to replace classical computers, but “merely” to complement them, accelerating specific tasks like quantum simulation and codebreaking.

I'm not sure about the field of physics but in deep learning there are hundreds of papers published every day while no more than a percent of them tries to make the paper less mythical and instead they keep inventing buzzwords and claiming positive results to make them even more mythical

Re: What You Shouldn't Know About Quantum Computers

#26

Post by _heimdall »

renonce wrote: post #25

> For example, would quantum computers work by trying all possible answers in parallel? Sorry, no, that's too good to be true: Quantum computers work by choreographing a pattern of interference, where the contributions to the amplitude of each wrong answer cancel each other out, while the contributions to the right answer's amplitude reinforce each other. Only for special problems, as it turns out, do we know how to…

That phenomenon isn't specific to physics or deep learning. Academic papers are more and more of a joke these days. Sure there's plenty of good work being done too, but its be buried in a pile of poorly done research and deceiving statistics that are written only to chase funding and/or recognition for the author (promotions, graduation, jobs, etc).

Re: What You Shouldn't Know About Quantum Computers

#27

Post by tromp »

sebzim4500 wrote: post #9
sampo wrote: post #7

> Researchers like Jaime Sevilla and Jess Riedel support this timeline, publishing a report in late 2020 that claimed a 90% confidence of RSA-2048 being factored before 2060. I am skeptical. 36 years is a long time, but in the past 10 years there hasn't been much progress: year 2001: factorization of 15 (IBM) year 2012: factorization of 21 (University of Bristol) year 2019: factorization of 35 attempt, failed (IBM) h…

IIRC none of those uses of shor's algorithm were real (well maybe the 2019 one was, but that failed). There's a threshold you need to reach for quantum error correction to work and we are approaching it pretty steadily on a log scale.

They were illegitimate instances of Shor according to [1]:

> Of course this should not be considered a serious demonstration of Shor’s algorithm. It does, however, illustrate the danger in “compiled” demonstrations of Shor’s algorithm. To varying degrees, all previous factorization experiments have benefited from this artifice. While there is no objection to having a classical compiler help design a quantum circuit (indeed, probably all quantum computers will function in this way), it is not legitimate for a compiler to know the answer to the problem being solved. To even call such a procedure compilation is an abuse of language.

[1] https://arxiv.org/pdf/1301.7007

Re: What You Shouldn't Know About Quantum Computers

#28

Post by threecheese »

bee_rider wrote: post #21
zeroonetwothree wrote: post #16

Earlier quoted context omitted.

It’s hard to make predictions, especially about the future.

When a prediction has a probability attached to it, it should be possible to check the math. In some sense it isn’t really a prediction about the future, so much as a statement about current information (which is not complete). Or, possibly, they are using “90% confidence” colloquially as “pretty sure.” If so, that should probably be made more clear. He’s using the fact that the researchers agree as an argument from…

It’s a quote, and you are gonna laugh when you find out who said it.

Re: What You Shouldn't Know About Quantum Computers

#29

Post by drdeca »

nyrikki wrote: post #19
sebzim4500 wrote: post #14

Earlier quoted context omitted.

>It must get exponentially harder per qbit to eliminate thermal noise by cooling down closer to absolute zero Why? Cooling a large object is not exponentially harder than cooling a small object.

Surface area is squared, volume is cubed, a larger object has to get hotter to expell the same amount of heat. Per unit of volume, your body produces more heat than the sun, exactly because it is an exponential function.

Huh? What are you saying is an exponential function?

x^3 is not an exponential function, in the sense relevant here.

Re: What You Shouldn't Know About Quantum Computers

#30

Post by mijoharas »

MrsPeaches wrote: post #5

Chris Ferrie also writes great books about science for babies. https://www.csferrie.com/books https://www.amazon.com/Quantum-Computing-Babies-Baby-Univers...

At first I saw that this was downvoted and assumed maybe it was a different Chris Ferrie, but from the looks of the blog it's the same person.[0]

Maybe other people thought this didn't add much to the discussion, but I found it interesting.

[0] I am Chris Ferrie, father of four and happy husband. My day job is academic research where I follow my curiosity through the world of quantum physics. My passion for communicating science has led from the most esoteric topics of mathematical physics to more recently writing children’s books.[1]

[1] https://www.csferrie.com/about

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