I’m not familiar with the original passage, but the assertion “the bits of knowledge obtainable about even prominent historical personages are far fewer than those describing a human mind” is questionable. If macroscopic decoherence is very reversible then it’s false, among other possible counters. Either way “so the resimulations are just approximations” could still be rather misleading considering many commonsense definitions of “approximation”. (I do not assume that khafra endorses Stross’s observations or that Stross made quite those observations, only that Stross made approximately those observations.)
I’m pretty sure I don’t… Wikipedia: “Viewed in isolation, the system’s dynamics are non-unitary (although the combined system plus environment evolves in a unitary fashion). Thus the dynamics of the system alone, treated in isolation from the environment, are irreversible. As with any coupling, entanglements are generated between the system and environment, which have the effect of sharing quantum information with—or transferring it to—the surroundings.”
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.
I’m not familiar with the original passage, but the assertion “the bits of knowledge obtainable about even prominent historical personages are far fewer than those describing a human mind” is questionable. If macroscopic decoherence is very reversible then it’s false, among other possible counters. Either way “so the resimulations are just approximations” could still be rather misleading considering many commonsense definitions of “approximation”. (I do not assume that khafra endorses Stross’s observations or that Stross made quite those observations, only that Stross made approximately those observations.)
That’s a very big if. Decoherence is often defined in terms of effective irreversability.
If a system’s dynamics are considered in isolation, then it’s theoretically irreversible, yes.
Don’t you mean reversible?
I’m pretty sure I don’t… Wikipedia: “Viewed in isolation, the system’s dynamics are non-unitary (although the combined system plus environment evolves in a unitary fashion). Thus the dynamics of the system alone, treated in isolation from the environment, are irreversible. As with any coupling, entanglements are generated between the system and environment, which have the effect of sharing quantum information with—or transferring it to—the surroundings.”
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.