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The need for quantum computers remains small

theregister.com

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Re: The need for quantum computers remains small

#51

Post by cycomanic »

O__________O wrote: post #17

Are quantum computers being used in economically significant ways that only are possible with quantum computers yet? If so, what is the best example? Last time I checked few years ago, my understanding was the answer was still no; specifically, believe I asked Scott Aaronson as a follow up question to a talk he gave: https://www.scottaaronson.com/

The short answer is no, I think Ising machines are much closer or even there for specific problems. They are somewhat similar to quantum computers, but entirely classical (Dwave was shown to be equivalent to an Ising machine IIRC).

Re: The need for quantum computers remains small

#53

Post by yccs27 »

feliyur wrote: post #45

From my limited understanding, a quantum computer performs computations over probability distributions, rather than over numerical values. Performing precise computations over probability distributions is a serious problem in many domains - physical simulations are just one. Another example is that could allow much more efficient and precise data fusion, and as a result - a leap in AI abilities, across domains where…

Unfortunately, even though a quantum computer "manipulates wavefunctions", you can still only measure the outcome once. The magic has to happen somewhere in between state preparation and measurement. It's more like a computer with an inbuilt RNG - but if you can reach the same result via multiple execution paths, the probabilities don't just add, but they can interfere like in-phase/out-of-phase oscillatins.

Re: The need for quantum computers remains small

#55

Post by seydor »

Quantum computers are a part of quantum mechanics that s more of a curiosity than something to be engineered at scale. There's so much more to explore in quantum mechanics outside computation that is not receiving commensurate funding. I guess it's because "computing" is what BigTech (who has the money to fund it) understands

Re: The need for quantum computers remains small

#56

Post by vanviegen »

rektide wrote: post #3

The need is high... for bad people doing bad things to everyone else (trying to de-secure the world)? There's some hypothetical travelling salesperson style questions we might ask. But we don't seem incapable of doing this work today. 98% the needs seem like: can we break the world's crypto. How is this anything beyond a chaotic evil mis-use? How will this do anything but de-secure & instigate risk across the planet?…

Breaking a coin's crypto doesn't sound all that amoral to me. People holding those coins have specifically chosen to put their financial faith in tech, instead of society (which they are arguably undermining).

A have less respect for those hacking the minds of the general public.

Re: The need for quantum computers remains small

#57

Post by throwawayffffas »

seydor wrote: post #55

Quantum computers are a part of quantum mechanics that s more of a curiosity than something to be engineered at scale. There's so much more to explore in quantum mechanics outside computation that is not receiving commensurate funding. I guess it's because "computing" is what BigTech (who has the money to fund it) understands

I was under the impression that it was because quantum computers would make the simulation of quantum mechanics significantly faster as well.

Re: The need for quantum computers remains small

#58

Post by nabla9 »

LeegleechN wrote: post #26

He's not wrong about the narrow algorithmic use cases (so far), but he's completely missing the utility for simulation of quantum phenomena (chemistry, microbiology, materials science). That use case alone completely justifies investing into them even if you don't care about advancing science.

> That use case alone completely justifies investing into them

Not at very massive scale of investments required.

Take for example, GPGPU (general purpose graphics processing unit). The wast investment needed to get there was funded by gaming industry. Supercomputers as a investment target were tiny compared to gaming and general purpose computing.

AI boom was created on a tails of gaming industry and the benefits spilled into scientific computing as well.

Re: The need for quantum computers remains small

#59

Post by bowsamic »

mtlmtlmtlmtl wrote: post #43
codeflo wrote: post #36

Earlier quoted context omitted.

The sceptic arguments I read focus on accidental decoherence during the computation. If that goes well, and classical computers only "catch up" during measurement, wouldn't this mean that the time cost of measurement has to scale super-polynomially? Is that plausible?

I got tired of speaking on behalf of a vague memory of Stephen Wolfram speaking that I just looked up the transcript. 6 SW: Yeah, I think… I think it’s not going to be true[that QC gives a speedup], that’s my guess. I think what’s going to happen is, if you take short algorithm for factoring, which is primarily a quantum Fourier transform, that Fourier transform is done beautifully quickly because there are all these…

That reads like Wolfram is generally pretty ignorant of the current state of quantum measurements. We can do continuous measurements now that barely perturb the system (Google “quantum non demolition” and “weak measurement”). Also while measurements are difficult to explain in QM (incompatible with Schrodinger equation) our theory of them is quite rich and complete now. This just seems rambling and imprecise from Wolfram. We can actually do the idealised measurement, which is why the standard quantum limit is such a big deal in gravitational wave detectors

EDIT: I should actually qualify the above, in order to surpass the standard quantum limit we will turn GW detectors into QND (quantum non demolition) detectors using techniques such as frequency dependent squeezing (see Kimble 2000) which is an ideal measurement

Re: The need for quantum computers remains small

#60

Post by cycomanic »

exmadscientist wrote: post #41
femto wrote: post #29

Earlier quoted context omitted.

Which leads onto computational medicine. The advent of SPICE [1] meant that with the right models electrical engineers could simulate complex electrical systems, do sensitivity analysis and make integrated circuits that had a high probability of working. Imagine a (quantum) simulator that can rapidly simulate all or part of the human body. The effects of medicines could be rapidly simulated, or the simulation could g…

Why do you believe a quantum computer can actually solve that problem? The whole point of the article is that quantum computers are not and can never be general-purpose computers. And something with as many inputs as "simulate the human body" seems like the exact opposite of what you can encode in qubits, evolve as a state vector, and usefully read out.

The point is that for these sort of simulations you don't want a general purpose computer. Ideally you have a "equivalent" of the quantum mechanical Hamiltonian that you can manipulate/design and read effects out from. Now to simulate the human body probably requires a prohibitively large number of qubits, however for many very useful things you don't need that.
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