{ 2016 08 24 }

Seth Lloyd on quantum information processing as a way of life

Quantum computers work by storing and processing information at the most microscopic level. For instance, if you have an electron, you could call an electron spinning out like this zero, you could call an electron spinning like that one, and you could call an electron spinning like that zero and one at the same time, which is the primary feature of quantum computation. A quantum bit—qubit—can be zero and one at the same time; this is where quantum computers gain their power over classical computers. …There is a special-purpose quantum computer, a quantum annealer, that’s made by a D‑Wave. This is a commercial device, and now a number of people have bought them. Lockheed Martin has bought a D‑Wave computer, Google and NASA have bought them, the Army is buying some of them. They’re buying them because they’re very interesting devices. Nobody understands exactly what’s going on inside them. They’re doing things that are quite mysterious in their own quantum mechanical way, because being mysterious is a quantum mechanical thing….D-Wave went along and built it … When they built it, it was indeed true that it didn’t behave in the way that you wanted it to behave—staying in the lowest energy state throughout the computation. It got excited to higher energy levels, but it still solves the hard problems. Why is this? Nobody knows….A few years ago, some friends of mine and I used a small quantum computer to simulate what happens in the process of time travel, because the theory of time travel is intrinsically quantum mechanical. If you want to find out what happens when you send a photon a few billionths of second backwards in time and have a try to kill its former self, well, we have experiment that tests to see what happens when you do that. … It turned out that one photon that tried to kill itself in the past always failed, because our quantum theory of time travel shows that you can’t go back and do something self-contradictory in the past, like kill your former self.

Posted by simon on Wednesday, August 24th, 2016, at 11:15 am, and filed under pique-assiettes.

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