Google claims to have proved its supremacy with new quantum computer • Hacker News Board

Re: Google claims to have proved its supremacy with new quantum computer

#211

Post by cohomologo » Tue, Jul 04, 2023, 3:56 AM UTC

Gravyness wrote: post #83

bob1029 wrote: post #6

Earlier quoted context omitted.

> The theoretical basis for these experiments depends on sampling the output distributions of random quantum circuits; unfortunately, understanding how this theoretical basis can be used to define quantum supremacy is an extremely difficult task. Anyone attempting to understand how this sampling task relates to quantum supremacy must study concepts from random matrix theory, mathematical analysis, quantum chaos, comp…

> This might be a case of a rabbit you do not want to chase. I'm sure the researchers will all collectively realize this, if it were to be the case, and disregard their 12 year academic journey with their great salaries in favor of research into more important topics like world hunger, renewable energy, etc. I'm so sure that the percentage of sureness is an imaginary, quantum-entangled value between -7 and 13 billion…

I research QC. Feel free to explain how my skills could be used to meaningfully contribute to the problem of world hunger or renewable energy while also keeping me employed --- going back to college to train in a different field isn't feasible. If it's not so easy, then perhaps it's logical that QC researchers and AI researchers and software devs aren't all jumping ship to work on "more important topics"...

You may just be spouting off, but I genuinely am asking. If someone else dissing QC research wants to make a pitch for a concrete plan on how to make a difference in the world with a physics PhD and years of experience in scientific computing, drop me a message.

Re: Google claims to have proved its supremacy with new quantum computer

#212

Post by cohomologo » Tue, Jul 04, 2023, 4:10 AM UTC

fsh wrote: post #5

Google's and IBM's previous "quantum supremacy" demonstrations were quickly crushed by improved classical simulations. Let's see if it survives this time.

True, but as someone who works on quantum physics using classical computers and loves to see classical computers simulating increasingly hard quantum problems, these "crushings" were still only done on classical computers in a way that would scale exponentially with the number of qubits.

Even then, I believe the classical simulations to beat google's 53 qubit device were never actually performed -- it was shown that they could be performed quickly with petascale memory but actually doing it would be a huge expense. Add a dozen more qubits and even the hypothetical classical challengers fall off quickly...

Re: Google claims to have proved its supremacy with new quantum computer

#213

Post by klyrs » Tue, Jul 04, 2023, 4:13 AM UTC

jl6 wrote: post #31

The ability to entangle particles feels like a really amazing new capability. (New in the last 100 years anyway). Like it’s a brand new kind of substance that has never been made before. Everything in all of history has been built out of boring old atoms, not these fancy new entangled things. Even if quantum computers turn out not to be able to solve interesting problems, I wonder if computers are the only thing we c…

Meh. They're just quasiparticles made out of bog standard particles.

Re: Google claims to have proved its supremacy with new quantum computer

#214

Post by pclmulqdq » Tue, Jul 04, 2023, 4:24 AM UTC

api wrote: post #193

bawolff wrote: post #191

Earlier quoted context omitted.

I don't think that is true, i imagine most people thought it was much more than 10 years away 30 years ago. I think 30 years ago people still weren't sure if it was physically possible at all. In the mean time real progress has been made. If we continue at this rate (big if) we will eventually have quantum computers. Just not tomorrow.

I think it’ll be like AI: perpetually 50 years away until some big discovery is made and everyone stops laughing. For AI it was the “attention is all you need” paper. I’ve been told that for QC it might be error correction that scales but I’m not knowledgeable enough to know if that’s true. I expect that nuclear fusion will follow the same trajectory of being 50 years away until it’s suddenly 0 years away. The realit…

Comparing to AI doesn't look so good for QC. The research that led up to the attention paper has a consistent trend of producing lots of useful applications for its 60-year history. You may not remember this, but in 2012 there was a computer vision "watershed moment" around the CNN architecture. Before that, there was the DARPA autonomous driving challenge and related research in robotics. Going back further, there have been many other big breakthroughs in ML/AI with immediate application, down to the perceptrons of the 60's and hidden markov models of the 70's. In other words, the field that eventually became AI was pretty much immediately useful.

The relative lack of useful intermediate results raises major red flags for me, but it doesn't seem that physicists are all that bothered by it. Indeed, the high energy theorists have been at it for longer with a lot less to show for their work: At least we have a few toy quantum computers, while there is still nothing testable about string theory.

Honestly, I hate to say this, but I think it's going to take a major war for QC to have its watershed moment (a "Manhattan project"), and I think the odds are that it will actually work if it comes to that. However, the window is kind of closing on the usefulness of the technology as post-quantum encryption starts to get legs, and I don't really want another World War 2...

Re: Google claims to have proved its supremacy with new quantum computer

#215

Post by EvgeniyZh » Tue, Jul 04, 2023, 4:40 AM UTC

deepburner wrote: post #197

EvgeniyZh wrote: post #195

Earlier quoted context omitted.

I don't agree. I do a bit of QC in my PhD, but my advisor works specifically on error mitigation, and from what I see, we'll soon (maybe a couple of years) be there: we'll have state-of-the-art simulations on quantum computer. There will be classical simulations that will improve on a specific claim, but eventually they'll die out. But even if it is not true, think how good can be QC without being good enough for qua…

You're talking in very vague terms here, what does """interesting""" mean? Let me give you some numbers. Factorising RSA is order 10^6 logical qubits (and I'm being charitable here), simulating FoMoCo is around 10^7. The state of the art error correction is around (again, charitably) 10^3 physical qubits per logical qubit at the moment, that gives us 10^9-10^10 qubits necessary for the simplest quantum application. W…

Well, I was talking specifically simulations of quantum systems (physical and chemical). Interesting is indeed vague, what I meant systems that people study outside of attempt to create a hard-to-simulate (classically) quantum system. Say, 2D Hubbard model or some 2D topological insulator.

Optimization (VQE, QAOA and stuff like that) also is realizable on NISQ. I'm more sceptical about its usefulness but it is hard to say.

Shor's algorithms is definitely outside of NISQ, I don't think anyone serious about QC thinks otherwise. From there to "no applications for NISQ" is a far fetch.

Re: Google claims to have proved its supremacy with new quantum computer

#216

Post by weard_beard » Tue, Jul 04, 2023, 4:57 AM UTC

mistermann wrote: post #168

weard_beard wrote: post #64

Earlier quoted context omitted.

The trick is you can only flip as yet unobserved bits. If we know the asteroid is coming we can't delete it.

Some bits can even be flipped in broad daylight while everyone's watching. One of the most popular ways to flip bits is by telling stories in which the bits have been flipped.

The power of stories is that you are alone in the telling of them. The survival, your own undressing, or redressing, the terrible fury of living life, constrained to the teacup of bedtime for children. The power that storytelling takes is a kind of leadership that is grudgingly respected, like a real bastard's funeral.

It doesn't have much to do with physics.

Re: Google claims to have proved its supremacy with new quantum computer

#217

Post by tsimionescu » Tue, Jul 04, 2023, 5:40 AM UTC

troupe wrote: post #97

The fact that the calculation would take 47 years on a classical computer is only a break through if the calculation is something we actually want to do. Otherwise it just means that we have created an unnecessary problem designed to be solved quickly by a quantum computer. That isn't to say that this quantum computer isn't impressive and a step forward. Just that the comparison isn't really meaningful unless the pro…

No one is claiming that general purpose quantum computers are useful right now. Instead, people are trying to prove that certain physical devices they have built behave like the theoretical model of a quantum computer.

To help prove that, people have found contrived problems that don't care about errors but that theoretical quantum computers can solve exponentially faster than classical computers. If these physical devices can solve those problems, that is proof that they are on the right path to one day solving actually interesting problems like Shor's algorithm.

There are of course some caveats. For one, the test problems discovered so far are believed to take exponentially more time on a classical computer, but there is no rigorous proof yet (in fact, it is not yet proven that there doesn't exist a classical algorithm that could run as fast as Shor's). The second is that the current quantum computers are so small compared to classical ones that, even with an exponential advantage, they can't always solve things fast enough to prove without a shadow of a doubt that they have this advantage. So, improvements in this time difference compared to the largest known classical computers is still a worthwhile goal.

Re: Google claims to have proved its supremacy with new quantum computer

#218

Post by chaboud » Tue, Jul 04, 2023, 5:54 AM UTC

riwsky wrote: post #179

chaboud wrote: post #156

Earlier quoted context omitted.

Sound effect libraries have long included the sounds of wood breaking/cracking, generally recorded (rather than simulated). A couple of jobs ago, we sold sound effect libraries that cost 2-5x the cost of the software applications that they were used with (hundreds to thousands of dollars). I think you’d be hard pressed to find economists (beyond freshman college students who recently discovered Nietzsche second hand…

You misunderstand me. It doesn’t matter how much the sound library is worth: if you weren’t using simulation to build it, then it’s irrelevant for the economic value of the simulation. Like, you can turn lead into gold if you run a nuclear reactor—and gold is valuable—but running this process is way more expensive than just buying gold, so it’s not valuable.

That’s classic cost benefit analysis, and there are plenty of examples in audio of trade offs where the simulation is sufficient (or more flexibly applicable). Just because the cost is high for a given application doesn’t mean something has no value. Bringing the cost down is the classic engineering conundrum.

Let’s take reverberation as an example:

- Folks used to record in big rooms for big room reverb. It’s nice, nuanced, and comically impractical. Place mics around the room and capture the effect live, but even your close-mic’d take is going to have the room in it.

- So some studios started piping audio out to a speaker in a secondary room and piping a mic from that secondary room back to the board. Boom. Configurable reverb, at your service.

- But you can’t take it with you, so spring and plate reverb devices showed up.

- Enter computers and DSPs, where simplified reverb models could be applied in real-time.

- And then on to impulse capture and convolution (e.g., pop a balloon in a church, record, convolve).

- And then beam tracing and other techniques approaching physical simulation (but orders of magnitude less computationally complex).

And all but piping to a second room were used in making the libraries of sounds that we sold.

However, throughout history, each of those techniques went through times then the cost benefit balance led to using some other technique(s) to achieve the desired result. That didn’t render those techniques worthless just because money hadn’t traded hands. It’s why economists describe markets as mechanisms for price discovery. What something had sold for is a way to understand value, but it’s not the sole definition of value (even monetary value)

Re: Google claims to have proved its supremacy with new quantum computer

#219

Post by hcks » Tue, Jul 04, 2023, 6:08 AM UTC

bawolff wrote: post #191

pclmulqdq wrote: post #188

Earlier quoted context omitted.

Quantum computing has been 10 years away for the last 30 years.

I don't think that is true, i imagine most people thought it was much more than 10 years away 30 years ago. I think 30 years ago people still weren't sure if it was physically possible at all. In the mean time real progress has been made. If we continue at this rate (big if) we will eventually have quantum computers. Just not tomorrow.

I’m curious, what “real progress” did QC make since the 90s?

Re: Google claims to have proved its supremacy with new quantum computer

#220

Post by jscipione » Tue, Jul 04, 2023, 6:15 AM UTC

Quantum computers make it practical for us to solve problems at much faster speeds, but at what cost? Quantum computers change the quantum state of particles in parallel universes, and likewise quantum computers in other universes change the quantum state of particles in our Universe. What is the effect of this? We should expect to see random otherwise unexplainable changes, and that’s exactly what we’ve seen over the last 10 years, it’s called the “Mandela Effect.”

But despite the name referring to an important historic figure most “mandela effects” are tiny almost insignificant changes such as the spelling of The Bernstein Bears or the presence of a Cornucopia in Fruit of the Loom logo, the kind of thing that quantum changes could alter. I realize this is probably too far out there for most Hacker News readers and I’ll get down-voted for it, but I believe there may be a real danger here, and it’s something we need to watch out for as we develop quantum computers further. If we don’t take the threat seriously the Universe we live in now may become different from the one we remember, and we will need to provide safe-guards to retain the consistency of our Universe.