[SRasch]

You were said to be a skeptic of quantum computing company d wave. Then you started believing and then went back to skepticism. What is your current status, do you think it works? What would you like to see from them?

Also, what is your take on Max Tegmark's quantum suicide experiment. Would it work? If yes would that imply that each of us should expect to live a really long time subjectively?

[ScottAaronson]

My position on the technical fundamentals never changed much: namely, D-Wave is building devices that could be interesting from various engineering perspectives, but that as far as most of us can tell, are not getting speedups over existing computers that are clearly attributable to quantum computation (as opposed to building special-purpose hardware that's, essentially, very fast at simulating itself). If you want quantum computing speedups, I think you're going to need qubits of much higher quality, and ultimately error correction or at least error mitigation. In principle, D-Wave could do that, and I applaud any steps they take in that direction. However, I'm personally much more excited right now about the experimental efforts in superconducting quantum computing that are happening at Google, IBM, Intel, and Rigetti -- all of which use qubits with orders-of-magnitude better coherence times than D-Wave's qubits. In some sense, D-Wave optimized for being able to say that they had 2000 qubits as quickly as possible, rather than for the qubits actually doing what we want.

On a more sociological level, D-Wave earned a lot of bad blood with the academic QC community by making false, inflated, and overhyped claims (with a primary offender being its founder, Geordie Rose, who's since left the company). And I certainly took them to task for those sorts of things on my blog. Then the D-Wave folks met with me, John Preskill, and other academics, and pledged to improve in how they communicated, so I was nicer to them for a while. Then they went back to egregious hype about speedups that weren't real, so I criticized them again. Nothing more to it than that. :-)

Regarding quantum suicide: no, I do NOT recommend killing yourself any time anything happens in your life that makes you unhappy, on the theory that other versions of you will survive, in other branches of the quantum-mechanical wavefunction where the bad event didn't happen. This is partly because, even assuming you accept the Many-Worlds Interpretation, "your" moral concern and responsibility presumably extend only to those branches that are in "your" future -- you have no contact with the other branches! And partly it's because I take it as almost an axiom of rationality that, if a metaphysical belief leads you to do "obviously insane" things with your life, then it's probably time to look for a better metaphysical belief. :-) (I wouldn't say the same about scientific or mathematical beliefs.)

[defen]

Another problem with the quantum suicide thought experiment is that there are plenty of branches where you end up alive but horribly disabled.

[martin1975]

Am I hearing this right, you think the whole multiverse concept is... meta-physics at best?

[tjhance7]

> This is partly because, even assuming you accept the Many-Worlds Interpretation, "your" moral concern and responsibility presumably extend only to those branches that are in "your" future -- you have no contact with the other branches!

Would you say that the only moral way to implement quantum suicide is with a Doomsday Device that would destroy the entire world, thus ensuring your actions won't affect anybody else even in the worlds where you die?