How Quantum Computers Could Kill the Arrow of Time
Here are some extracts:
Very orderly and very random systems are easy to predict. (Think of a pendulum — ordered — or a cloud of gas filling a room — disordered.) In this paper, the researchers looked at physical systems that had a goldilocks' level of disorder and randomness — not too little, and not too much. (So, something like a developing weather system.) These are very difficult for computers to understand, said study co-author Jayne Thompson, a complexity theorist and physicist studying quantum information at the National University of Singapore. [Wacky Physics: The Coolest Little Particles in Nature]
Next, they tried to figure out those systems' pasts and futures using theoretical quantum computers (no physical computers involved). Not only did these models of quantum computers use less memory than the classical computer models, she said, they were able to run in either direction through time without using up extra memory. In other words, the quantum models had no causal asymmetry.
"While classically, it might be impossible for the process to go in one of the directions [through time]," Thompson told Live Science, "our results show that 'quantum mechanically,' the process can go in either direction using very little memory."
And if that's true inside a quantum computer, that's true in the universe, she said.
Quantum physics is the study of the strange probabilistic behaviors of very small particles — all the very small particles in the universe. And if quantum physics is true for all the pieces that make up the universe, it's true for the universe itself, even if some of its weirder effects aren't always obvious to us. So if a quantum computer can operate without causal asymmetry, then so can the universe.
Of course, seeing a series of proofs about how quantum computers will one day work isn't the same thing as seeing the effect in the real world. But we're still a long way off from quantum computers advanced enough to run the kind of models this paper describes, they said.
What's more, Thompson said, this research doesn't prove that there isn't any causal asymmetry anywhere in the universe. She and her colleagues showed there is no asymmetry in a handful of systems. But it's possible, she said, that there are some very bare-bones quantum models where some causal asymmetry emerges.
And if that's true inside a quantum computer, that's true in the universe, she said.
ReplyDeleteOnly if you believe the universe is an entirely bottom up process. We've never seen causal asymmetry in the classical realm.
No, it's the other way around, isn't it? In the classical realm, we see causal asymmetry all the time.
ReplyDeleteIt's the use of negatives in "without causal asymmetry" that makes it confusing, I think - I first thought you had it wrong, then thought I had got it mixed up, then went back to it being wrong.