[doubleunplussed]

The qbits and unitaries don't have to be perfect - it's about how things scale when you add qbits. Quantum error correction shows that you can add more qbits to make up for imperfection, and still be left with a quantum computer, i. e. the imperfection hasn't demoted the thing to a classical computer.

Of course they haven't built one yet, but none of the difficulties encountered so far have involved discovering new physics, which is what you would need to do to rule out quantum computers since the laws of physics as currently understood permit them.

[scottlocklin]

You've just regurgitated Aaronson's statement on the topic. Aaronson never studied physics, and has probably never fiddled with an op-amp or tried to make entangled anything in the world of matter. There's zero evidence quantum error correction will work; it's just an idea with no basis in the world of matter. There's zero evidence you can meaningfully and usefully manipulate quantum coherent states, let alone manipulate an exponentially huge number of them with a polynomially large number of computational elements, which is the essential claim of quantum computing. They make great claims: great claims need evidence; not theoretical wankery. Building a couple of scalable error corrected qubits would be a great start; it might even cause me to shut up about it.

Never in the history of the human race has something as complex as a computer architecture existed in the theoretical world before it exists in some form in the physical world, let alone one for which we define complexity classes.

The entire field is intensely silly, and the last time I said so in a public place, the waiter turned out to be some dude who just got his Ph.D. in the subject. He didn't agree with me exactly, but the fact the dude had a job bringing people steaks for a living is a decent argument I'm right.

[doubleunplussed]

My arguments are my own. I am an atomic physicist, and I meaningfully and usefully manipulate coherent quantum states every day. Not for making a quantum computer mind you, but quantum states nonetheless. Quantum mechanics works. The atoms do exactly what the Schrödinger equation says they should, however much entanglement is added. We are yet to see it break down. Plenty of my colleagues are working on quantum computers, with atoms, ions, photons, and solid state systems, and from where I stand it doesn't look like nonsense. It looks steady progress, and if there are insurmountable barriers, they have not yet been encountered.

I am not certain that quantum computers are possible, but I am certain that you are wildly overconfident that they are not.

[scottlocklin]

How much money are you willing to stake on that statement? I'll make a market for you; if you think your education gives you an edge over the wildly overconfident guy -we can even stick it on a blockchain that is quantum future proof if you like. Your choice.

Saying "quantum mechanics works" is not the same as saying "I can manipulate exponential QM states with polynomial imperfect physical devices." In the early days, people sketched out optical quantum computers that totally worked, but had exponential growth in elements with quantum states. Which, I bet, is how the universe is always going to work.

Money where your mouth is: I haven't found any other good shorts for this shitty idea.

[doubleunplussed]

I asked you elsewhere in the thread what odds you're willing to bet at, so absolutely I'm willing to put my money where my mouth is. I'll happily bet that there will be a demonstration of 'quantum supremacy' within 20 years - that is, a quantum computer computing something faster than a classical computer, whether it's Grover's algorithm or factoring or something else. Let's say by the 1st of July 2039.

I'm not super confident there will be quantum computers, whereas you seem very confident there will not be. What do you think the probability of quantum supremacy within 20 years is? If you think it's 5 % and I think it's 50 %, perhaps we can take the geometric mean and bet at 6:1 odds (~15% chance).

Will you give me those odds? Let's say I stake $200. Then I'd give you that if I lose, and you'd give me $1200 if I win. Or we can increase the amount a bit. Today's dollars, we can inflation adjust since it'll be 20 years.

The terms might sound favourable to me, but you seem very confident that there won't be quantum computers ever, so less than 15% chance in the next 20 years seems consistent with your belief.

I wouldn't know how to put the bet on a blockchain, but if you know about that and want to, I'm happy. Otherwise I am happy to just take your word.

We can also shorten the duration of the bet, but I would want to shift the odds a bit since although I think quantum computers have a decent chance of being possible, there is considerable uncertainty in how long it would take to get to the point of demonstrating quantum supremacy. Probably I would accept doubling the odds if the duration of the bet were halved and so on.

[scottlocklin]

We'd need a hard definition of "quantum supremacy" -I believe there have been several press releases claiming this already, and I think you agree with me that there are no such machines at hand.

There's this ethereum thing called Augur we could use to place the bet, though that's an interesting bet in itself (ethereum and auger being around in 20 years is not a sure thing). I suppose also "long bets." If you google my name you can find my contact info.