Jul 27, 2018 03:15 PM
(This post was last modified: Jul 27, 2018 03:16 PM by C C.)
https://www.livescience.com/63182-quantu...-time.html
EXCERPT: . . . It's much easier for a bit of software running on your laptop to predict how a complex system will move and develop in the future than it is to recreate its past. A property of the universe that theorists call "causal asymmetry" demands that it takes much more information — and much more complex calculations — to move in one direction through time than it does to move in the other. [...]
Information theorists suspected for a long time that causal asymmetry might be a fundamental feature of the universe. As long ago as 1927, the physicist Arthur Eddington argued that this asymmetry is the reason we only move forward through time, and never backward. If you understand the universe as a giant computer constantly calculating its way through time, it's always easier — less resource-intensive — for things to flow forward (cause, then effect) than backward (effect, then cause). This idea is called the "arrow of time."
But [...] A team of researchers found that in certain circumstances causal asymmetry disappears inside quantum computers, which calculate in an entirely different way [...] And, even more enticingly, their paper points the way toward future research that could show causal asymmetry doesn't really exist in the universe at all.
[...Jayne Thompson said...] "While classically, it might be impossible for the process to go in one of the directions [through time] ... 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.
[...] This paper doesn't prove that time doesn’t exist, or that we’ll one day be able to slip backward through it. But it does appear to show that one of the key building blocks of our understanding of time, cause and effect, doesn't always work in the way scientists have long assumed — and might not work that way at all. [...] The real practical benefit of this work [...] is that way down the road quantum computers might be capable of easily running simulations of things (like the weather) in either direction through time, without serious difficulty. That would be a sea change from the current classical-modeling world.
MORE: https://www.livescience.com/63182-quantu...-time.html
EXCERPT: . . . It's much easier for a bit of software running on your laptop to predict how a complex system will move and develop in the future than it is to recreate its past. A property of the universe that theorists call "causal asymmetry" demands that it takes much more information — and much more complex calculations — to move in one direction through time than it does to move in the other. [...]
Information theorists suspected for a long time that causal asymmetry might be a fundamental feature of the universe. As long ago as 1927, the physicist Arthur Eddington argued that this asymmetry is the reason we only move forward through time, and never backward. If you understand the universe as a giant computer constantly calculating its way through time, it's always easier — less resource-intensive — for things to flow forward (cause, then effect) than backward (effect, then cause). This idea is called the "arrow of time."
But [...] A team of researchers found that in certain circumstances causal asymmetry disappears inside quantum computers, which calculate in an entirely different way [...] And, even more enticingly, their paper points the way toward future research that could show causal asymmetry doesn't really exist in the universe at all.
[...Jayne Thompson said...] "While classically, it might be impossible for the process to go in one of the directions [through time] ... 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.
[...] This paper doesn't prove that time doesn’t exist, or that we’ll one day be able to slip backward through it. But it does appear to show that one of the key building blocks of our understanding of time, cause and effect, doesn't always work in the way scientists have long assumed — and might not work that way at all. [...] The real practical benefit of this work [...] is that way down the road quantum computers might be capable of easily running simulations of things (like the weather) in either direction through time, without serious difficulty. That would be a sea change from the current classical-modeling world.
MORE: https://www.livescience.com/63182-quantu...-time.html
