[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.

[red75prime]

Yet another problem with that is no matter how small the measure of those branches is, you'll end up in them anyway.

The death of natural causes qualifies too.

[martin1975]

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

[AgentME]

I think he was saying about whether you should morally care about the other branches counted as meta-physics.

[ScottAaronson]

Yup.

[JakeTyo]

You simply can't something 'physics' if its not testable. :)

[martin1975]

That word 'testable', is very loaded. :) But I get what you mean. Are there things that we can't test that do exist?

[AgentME]

>Are there things that we can't test that do exist?

There's many reasons to believe that objects that exit our light cone continue to exist after they do, even though they could never have any future interaction with us to confirm that. (Say a spaceship leaves Earth at near the speed of light in a straight line, and then enough time passes that the space between the ship and Earth is expanding so fast that the spaceship or any kind of signal from the spaceship would have to travel faster than light to return to Earth, which is impossible. Believing that the spaceship disappears when it exits our light cone requires believing in unnecessarily more complicated physics.)

[joshuamorton]

Scientifically speaking, no. A scientific hypothesis must be falsifiable, and to be falsifiable it must be testable. I guess in some sense you could claim that there are hypothesis that are testable, but which we do not have the capacity to test. But then, is the claim that "one day in the future, we will be able to test this other claim" itself falsifiable? I'd argue not (it's a recognizable, not decidable claim, in the computational sense, and I think that for a claim to be falsifiable, it must be decidable).

[kybernetikos]

> A scientific hypothesis must be falsifiable

This is certainly one understanding about what science should be (although not a scientific one interestingly enough). Personally I prefer Thomas Kuhn's demarcation, which by my understanding concentrates more on whether a scientific program is producing interesting predictions which turn out to be true.

[kybernetikos]

> Are there things that we can't test that do exist?

Lots of people think so (e.g. unmeasurable things predicted by theory like parallel universes, but also things like evil or God or the color purple), but by definition it's hard to be very sure, or to transfer your own confidence in such things to others.

Lots of these kinds of questions reduce to quibbling about definitons; and also by definition, if we can't test the thing then the universe isn't going to punish us either way for believing or not.

[mygo]

> if we can't test the thing then the universe isn't going to punish us either way for believing or not.

If we can’t test the thing then what we are discussing is faith, not science.

Nothing wrong with faith and beliefs but I think it’s important to differentiate between these things and science because often times science is used as a basis for untestable beliefs and then people really start to think that those untestable beliefs are actually backed by scientific research.

[mygo]

Despite the scientific method giving rise to the fact-based ever-improving test-able body of work we call Science.. that doesn’t stop people from creating their own religions and beliefs based on it.

[ianai]

I think there’s a grave misunderstanding about the multi-universe interpretation. The scales at which the uncertainty principle come into play are vastly small. I think they’re small enough that they don’t summate to larger scale variances. The larger level probably asymptotes to the one reality.

[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?

[ScottAaronson]

No, I wouldn't recommend that either. :-)