An Argument Against Quantum Computers

Really interesting contrarian opinion although I wish he had expanded a bit when he said this:

I agree that these are unusual and perhaps even strange lines of analysis.

Here is a paper Kalai published that obviously goes into a lot more depth than the interview. https://arxiv.org/abs/1605.00992

I think he is referencing several theorems about fault tolerant computing. I think the reasoning goes that if we assume some level of correlated noise, then these theorems tell us we need an error correcting code that runs in O(e^n) where n is the number of quibits in the program you want to check for errors. I could be wrong though, see my comment above where I link to the paper.

If it really is exponentially more difficult to correct for noise as the number of qubits increases, then it will be impossible to build a useful quantum computer. We may not be able to say whether it's impossible after 24 qubits, or after 29, or after 32, etc., but we may be able to know that it's impossible to build anything useful, if someone can rigorously mathematically prove this.

On the other hand if nobody can provide a mathematical proof that it's impossible, it could just be engineering. Then again, "just engineering" doesn't prove a useful quantum computer may require practically impossible configurations (i.e., having to be in the middle of a sphere of lead dozens of miles in radius cooled to near absolute-zero is not necessarily impossible, but isn't something we're going to build anytime soon), or that we simply won't be able to figure out the requisite configurations.

Alternatively, this guy will prove to be wrong and someone will just build a quantum computer with a couple hundred qubits, at which point we may have enough data to observationally draw the curve rather than via math and the simplifications required to make it tractable, and maybe it'll be fine.

I love that the journalist asked ”What do your critics say to that?”, and that the researcher gave a meaningful, non disparaging reply. This should be expected from everyone doing research work, but is sadly far from the norm.

It’s along the same lines as, in a debate, asking each participant to sum up their opponent’s point of view in a way that they agree with. A fundamental tool for productive discourse.

Really enjoyed the interview.