For a decade or two, Caltech professor of physics John Preskill has given many excellent talks and lectures about quantum computing (and also about high energy physics, his original specialty). Much of this material can be found at his Caltech webpage, which is a pleasure dome for physics nerds.

Ten years ago, Preskill gave a wonderful talk, one with very little math, understandable by most physics undergrads, entitled

Quantum Computation and the Future of Physics (delivered at the Berkeley Workshop on Theory of Computation and the Sciences. – 10 May 2002)

The title alone invites endless speculation. Quantum computing is likely to change considerably the technology landscape, but what about “fundamental” physics? Will it change that too very much or not much at all?

All of the talk is interesting, but there is one transparency that I find particularly intriguing (transparency number 48 out of 49). Here it is:

So he thinks Matrix M-theory cannot be simulated efficiency by a quantum computer, although quantum field theory can be. Or at least he thought this 10 years ago. I wonder if he has changed his mind since then. I hope Preskill will be proven wrong (or right) in the near future by someone. String Theorists, get to work.

Should physical theories be required to satisfy certain complexity constraints, and can such requirements serve to winnow out a lot of bad theories? Maybe if the *time evolution* of a version of string theory cannot be simulated with polynomial efficiently, on a quantum computer, then that version of string theory should be considered kaput and verboten?

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Any criteria to disqualify String theory variation to hopefully eventually arrive at something that can be properly experimentally tested is most welcome. I was a child when I first learned about the existence of String theory (back then it was shiny and new). I don’t want to pretend that I understand its intricacies better now than I did back then, but the fact that after so many years very few tests have been conducted (and the ones that were came back negative), definitely rubs me the wrong way.

Comment by Henning Dekant — June 16, 2012 @ 4:30 am

[…] theories can be efficiently simulated on a quantum computer. But it has been suggested that those that cannot should be considered unphysical. Share:Share This entry was posted in Popular Science, Quantum Computing. Bookmark the permalink. […]

Pingback by Feynman would have approved | Wavewatching — July 9, 2012 @ 2:31 am

[…] This summer a paper was published (Science June 1st issue) that showed conclusively that for this new breed of machine a polynomial scaling of these notorious calculations is indeed possible. (As for String theory simulations, the jury is still out on that – but it has been suggested that maybe it should be considered as an indication of an unphysical theory if a particular flavor of a String theory cannot be efficiently simulated on a quantum computer). […]

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