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Simulating quantum 'time travel' disproves butterfly effect in quantum realm:
Using a quantum computer to simulate time travel, researchers have demonstrated that, in the quantum realm, there is no "butterfly effect." In the research, information—qubits, or quantum bits—'time travel' into the simulated past. One of them is then strongly damaged, like stepping on a butterfly, metaphorically speaking. Surprisingly, when all qubits return to the 'present,' they appear largely unaltered, as if reality is self-healing.
[...] In the team's experiment, Alice, a favorite stand-in agent used for quantum thought experiments, prepares one of her qubits in the present time and runs it backwards through the quantum computer. In the deep past, an intruder—Bob, another favorite stand-in—meaures[sic] Alice's qubit. This action disturbs the qubit and destroys all its quantum correlations with the rest of the world. Next, the system is run forward to the present time.
According to Ray Bradbury, Bob's small damage to the state and all those correlations in the past should be quickly magnified during the complex forward-in-time evolution. Hence, Alice should be unable to recover her information at the end.
But that's not what happened. Yan and Sinitsyn found that most of the presently local information was hidden in the deep past in the form of essentially quantum correlations that could not be damaged by minor tampering. They showed that the information returns to Alice's qubit without much damage despite Bob's interference. Counterintuitively, for deeper travels to the past and for bigger "worlds," Alice's final information returns to her even less damaged.
"We found that the notion of chaos in classical physics and in quantum mechanics must be understood differently," Sinitsyn said.
The more damage you do in the past, the less the present is affected?
(Score: 2, Disagree) by Common Joe on Thursday July 30 2020, @01:31PM (1 child)
It sounds like you're arguing for parallel worlds -- which I would say isn't strict time travel.
(Score: 2) by ledow on Thursday July 30 2020, @02:43PM
It's the same, in both. It's not parallel worlds as such - that would be further dimensions like ours that are out there running other universes like ours.
Just extra dimensions to our own. It's like earth people suddenly realising they could go "up" rather than just along the lay of the land.
It's not (necessarily) lots of universes next door, it's the same universe but with dimensions that we don't use, where particles (but not necessarily even substantial matter) have always had all the dimensions, we just never used/witnessed them.
We're 3.5D beings in an 11+D universe. There's nothing to suggest that our D's are anything special at all, and it would be odd if our D's were "replicated" somehow... it's the same set of D's most likely.
But (0,0,0,0) in our universe is really (0,0,0,0,0,0,0,0,0,0,0), and those last digits changing just means that we're not part of the world. It's like being on a perfectly straight railroad track and then realising you could build another at right-angles to it. Somewhere in there, when you travel along the new track, there may be other railroads heading in the same direction as our original, but, of course, being dimensionally separate, we'd never have known about them.
And with time being just the fourth 0, we have no idea where it would be possible to travel along that. But it would be time travel. It might show us our past railroad, or our future railroad, or we might cross paths with other railroads. It's no different to any other dimension - when we near "0" on that co-ordinate, we near our origin point/time. When we stray from it, we get further away in distance/time in one direction or another.
But there's nothing to say that when you're at (0, 0, 0, 0, 10000000, ....) that there's any way to tell our universe at (0,0,0,0) even exists. You're so far away, you'd never know.
To a particle that can just traverse any set of coordinates because the maths lets it, and it ends up with a velocity on one of those extra dimensions, we'd appear to distance ourselves until it returned to something near our coordinates. And it would disappear from our existence entirely because we can only see the first four, and only a tiny fraction of one of those (i.e. what's here NOW).
When dimensions are just coordinates, and travelling is just maths on a certain axis, then time travel is just heading in a certain direction, no different to walking off to the side of the railroad.