New Paper Calls Quantum Computing a Big Failure

Dr. Quantum Supremacy responds to a new paper:

A week ago, a philosopher named Amit Hagar put out a preprint entitled The NISQ Trap: Eight Years of Demonstrations the Hardware was Built to Lose. Here’s the abstract:

With a single clear exception, every NISQ-era flagship demonstration of ‘quantum advantage’ has, within eighteen months of its announcement, been classically reproduced, shown to rest on classically tractable structure, or closed by a simulability theorem.

Nevertheless, the basic thesis — that quantum supremacy in the NISQ (Noisy Intermediate Scale Quantum computing) era has been a failure, or even an example of pathological science — seems surprisingly widely shared, along with the opposite thesis that quantum computing already gives oodles of useful advantages for optimization and finance. ...

You’re right that, if you just look at the commercial value right now versus money spent to date, quantum computing looks like a colossal waste — as did classical computing before it scaled, as did nuclear power and heavier-than-air flight and every other nontrivial new technology.

Nobody invested a nickel in those other technologies, until someone had a proof of concept. Quantum computing is different in that it has attracted many billions of investment dollars, without a proof of concept, or a business plan on how it would ever make money.

This response is very weak. Go ahead and read it and decide for yourself. Someone publishes a paper saying the whole field has been a failure for 20 years, he admits that the view is widely shared, but says new technologies take time.

And of course he falls back on the argument that quantum computers have not been proved impossible:

Yes, the “real” goal remains, as it’s been since the 1990s, to build a scalable fault-tolerant quantum computer — and I’m glad that Hagar (unlike, say, Gil Kalai) never suggests that we’ve learned anything to rule that goal out. In the meantime, an intermediate goal would be to use NISQ devices to do physics and chemistry simulations that are commercially useful, or that help solve important scientific problems. The point of quantum supremacy experiments, you might say, is that by demonstrating the reality of quantum speedup about as clearly as it can be demonstrated with current hardware, they let us cleanly turn our attention to those more ambitious goals.

Hagar does not even talk about whether quantum computers are possible. His point is that they are empirical failures.

Update: Aaronson says:

For me, though, the real game always has been to learn the truth or falsehood of the Extended Church-Turing Thesis: that is, can all of nature be simulated on a standard Turing machine with polynomial overhead, or is quantum mechanics a counterexample to this? And from that standpoint, it seems obvious to me that the burden of proof lies with those who think the Extended Church-Turing Thesis still holds in a quantum-mechanical universe. Why does it hold? What astonishing new principle causes it to hold, despite the exponentially many canceling terms that generically arise in a path integral?

I get enraged when (some) QC skeptics seem not even to notice these profound questions, and content themselves to poke holes in this or that specific quantum fault-tolerance proposal and then call it a day. That seems to me to reflect a staggering incuriosity about the way the world actually is.

I am probably one of those enraging him. I agree that the big question is whether quantum computers can outdo Turing machines. Since he is a leading expert and he regards this as still an open question, then I accept that it is unsettled.

I disagree about the burden of proof. I say that a new technology should show that it works. He says the burden of proof is to show that it does not work.

The profound question is to understand why it does not work. I am somewhat incurious about this, because I am not sure any explanation will be fully satisfactory. Do we understand why F=ma, or how gravity workds, or why nothing goes faster than light, or why perpetual motion machines are impossible? Yes, I know the textbooks have explanations, but they do not stop people from theorizing about them, so apparently the explanations are not totally convincing.

That Extended Church-Turing Thesis was widely accepted for 50 years, including by very smart physicists who understood quantum mechanics. If quantum supremacy were possible, I would think that someone would have demonstrated it by now.

Update: Gil Kalai Says:

I also tend to agree with Amit’s conclusion that the quantum supremacy claims are either false or inconclusive. ...

For more than two decades, Scott has argued that the burden of proof lies on the shoulders of the skeptics. I suggest that we split the burden of proof as follows:

The burden of showing that the engineering obstacles to high-quality quantum error correction and quantum fault tolerance are not far beyond reach lies with the proponents of quantum computing. They still have a long way to go before providing convincing evidence that these goals are feasible and can be achieved in the foreseeable future.