Quantum reversibility is relative, or does a quantum measurement reset initial conditions?

Area of Science:

• Physics
• Quantum Mechanics
• Information Theory

Background:

• Classical and quantum dynamics differ in their treatment of information and reversibility.
• Measurement in quantum mechanics fundamentally alters the system and observer's state.

Purpose of the Study:

• To compare the role of information in classical versus quantum dynamics.
• To investigate how information flow during measurements affects the reversibility of evolutions.
• To analyze the impact of information gain on quantum irreversibility.

Main Methods:

• Comparative analysis of information flow in classical (Newtonian) and quantum dynamics.
• Examination of the relationship between measurement outcomes, information retention, and evolutionary reversibility.
• Introduction of quantum discord as a measure of information dissemination's effect on reversibility.

Main Results:

• In Newtonian dynamics, information retention by an observer does not impact reversibility.
• Quantum evolution leading to a measurement becomes irreversible for an observer who records the outcome.
• Quantum irreversibility arises from information gain, not solely entropy increase.
• A third party (observer's friend) can reverse quantum measurements if they know the outcome but not the result.

Conclusions:

• Quantum mechanics exhibits a relativity of reversibility dependent on information access.
• Information gain, not just loss, can drive irreversibility in quantum systems.
• This sheds light on the arrow of time and the fundamental role of information in physics.
• Quantum discord quantifies the impact of information dissemination on reversing quantum measurements.