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Manfred comments on Open thread, 16-22 June 2014 - Less Wrong Discussion
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So, I'm curious - how should we update on the probability of time travel, given this?
(Sorry about the paywall. The content, filtered through my undergraduate understanding of QM: essentially, researchers prepared a quantum simulator mathematically equivalent to a CTC and got reasonable results from it that matched up with David Deutsch's predictions.)
Essentially unchanged. Implementations of these things are usually done so that if quantum mechanics works, it will work.
But we don't know that quantum mechanics works on the edges, particularly the ones that give infinities or weird things like CTCs. Shouldn't the confirmation that it does, in fact, continue to work, increase our likelihood of time travel being possible in general?
This is not the edges. The paper is about a simulation, not actual time travel. Simulated time travel, following typical rules, is just a regular ol' quantum system that you assign extra meaning to. It was provable that this would work - though still a technical challenge to make it happen.
Except - and apologies if I'm wrong, since I don't completely understand the article - it seems like they first proved that this was equivalent (under current understanding of QM) to a system that includes a CTC.
So it looks like it's proving "If quantum mechanics works, this describes a CTC."
They ignore relativity completely and simulate qubit interaction on a background spacetime with CTCs. Interesting, but has nothing to do with testing the limits of QM.
Ah, I see. Thanks.