If you draw a notional, boundary around a system that is embedded in an environment and consider it in isolation, then you introduce an asymmetry due to the information lost crossing the boundary.
The system+environment evolves in a unitary fashion, but you can’t do anything to reverse the universe.
The only hope of reversing is a system is if it actually is isolated...inot interacting with with an environment.
The environment can be larger than whatever system you drew a notional boundary around and still smaller than the universe, so not being able to reverse the universe isn’t a problem. Here, I’ll make it explicit: imagine it turns out that your “environment” is actually a Laplacian monstrosity! You’re just a subsystem. All concerns about irreversibility are thenceforth questionable.
If you draw a notional, boundary around a system that is embedded in an environment and consider it in isolation, then you introduce an asymmetry due to the information lost crossing the boundary.
The system+environment evolves in a unitary fashion, but you can’t do anything to reverse the universe.
The only hope of reversing is a system is if it actually is isolated...inot interacting with with an environment.
(relevance to quantum computing)
The environment can be larger than whatever system you drew a notional boundary around and still smaller than the universe, so not being able to reverse the universe isn’t a problem. Here, I’ll make it explicit: imagine it turns out that your “environment” is actually a Laplacian monstrosity! You’re just a subsystem. All concerns about irreversibility are thenceforth questionable.