Loschmidt's paradox-II: Quantum Decoherence

In summary, Loschmidt's paradox, also known as the reversibility paradox, questions the possibility of deducing irreversible processes from time-symmetric dynamics. The question remains how time-asymmetric Quantum Decoherence can emerge from time-symmetric Quantum Mechanics, but it is believed to be similar to how the time-asymmetric second law of thermodynamics arises from classical time-symmetric equations of motion through special initial conditions and coarse graining. Weak CP violation is not thought to play a role in this emergence.
  • #1
Dmitry67
2,567
1
So if you remember, Loschmidt's paradox is about "Loschmidt's paradox, also known as the reversibility paradox, is the objection that it should not be possible to deduce an irreversible process from time-symmetric dynamics" ( http://en.wikipedia.org/wiki/Loschmidt's_paradox )

My question is, how time-assymetric Quantum Decoherence emerges from time-symmetric Quantum Mechanics?

P.S. I don't think weak CP violation (which leads to T-symettry violation) plays any role in it.
 
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  • #2
Isn't it simply that the wave-function of the universe/multiverse as a whole is time reversible, even though we can inspect it from a basis in which each part is not reversible? In other words, there's nothing preventing the SE from back-evolving a superposition of "observed dead cat" plus "observed live cat" into "haven't yet opened the box"; apparent asymmetry arises from our (self-centred) choices to ignore/drop part of the final superposition.

(And classicaly, there is no paradox in time-symmetric laws predicting that if the universe had low entropy at its lower bound of time then it will have entropy increasing with time.)
 
  • #3
Dmitry67 said:
My question is, how time-assymetric Quantum Decoherence emerges from time-symmetric Quantum Mechanics?
Essentially, the same way how time-asymmetric second law of thermodynamics emerges from classical time-symmetric equations of motion:
Special initial conditions + coarse graining -> time-asymmetry
 

FAQ: Loschmidt's paradox-II: Quantum Decoherence

What is Loschmidt's paradox-II?

Loschmidt's paradox-II, also known as the reversibility paradox, is a thought experiment in physics that questions the reversibility of the laws of thermodynamics. It poses the question of whether or not the microscopic laws of physics are reversible, even though the macroscopic laws of thermodynamics appear to be irreversible.

What is quantum decoherence?

Quantum decoherence is the process by which a quantum system interacts with its surrounding environment, causing the system to lose its quantum behavior and become classical. This occurs due to the entanglement between the system and its environment, leading to the collapse of the wavefunction and the loss of coherence.

How does quantum decoherence relate to Loschmidt's paradox-II?

Quantum decoherence is often used to explain the apparent irreversibility of macroscopic events, which is the central issue in Loschmidt's paradox-II. It suggests that the seemingly irreversible behavior of macroscopic systems is a result of the loss of quantum coherence due to interactions with the environment.

What are the implications of quantum decoherence for Loschmidt's paradox-II?

The implications of quantum decoherence for Loschmidt's paradox-II are still being debated and researched. Some scientists believe that it provides a solution to the paradox by explaining the apparent irreversibility of macroscopic events. Others argue that it simply shifts the paradox to the question of why quantum systems become entangled with their environment in the first place.

Is Loschmidt's paradox-II still relevant in modern physics?

Yes, Loschmidt's paradox-II is still a relevant topic in modern physics, particularly in the field of quantum information and quantum computing. The issues raised by the paradox continue to challenge our understanding of the fundamental behavior of physical systems and the nature of time and irreversibility.

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