Decoherence of measurement outcomes

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SUMMARY

The discussion centers on the decoherence of measurement outcomes in quantum systems, specifically addressing the statement from a quantum information theory paper regarding the loss of coherences between measurement outcomes in the joint state of the apparatus (A) and the quantum system (Q). It is established that these coherences dissipate into the environment (E) during the system's dynamical evolution, leading to the emergence of pointer states that facilitate decoherence. The initial state of the combined system is represented as ##\rho^{(AEQ)} = \rho_{0}^{(AE)}\otimes \rho^{(Q)}##, highlighting the interaction between the quantum system and its environment.

PREREQUISITES
  • Understanding of quantum states and density matrices, specifically ##\rho^{(Q)}## and ##\rho^{(AE)}##.
  • Familiarity with the concept of decoherence in quantum mechanics.
  • Knowledge of quantum measurement theory and pointer states.
  • Basic grasp of quantum information theory principles.
NEXT STEPS
  • Research the concept of quantum decoherence and its implications on measurement outcomes.
  • Study the role of pointer states in quantum measurements and their relationship with the environment.
  • Examine the mathematical formulation of density matrices in quantum mechanics.
  • Read the referenced quantum information theory paper for deeper insights on the topic.
USEFUL FOR

This discussion is beneficial for quantum physicists, researchers in quantum information theory, and students studying quantum mechanics, particularly those interested in the implications of decoherence on measurement processes.

Johny Boy
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Suppose we have a quantum system ##Q## with an initial state ##\rho^{(Q)}##. The measurement process will involve two additional quantum systems: an apparatus system ##A## and an environment system ##E##, hence giving the initial state of the system ##\rho^{(AEQ)} = \rho_{0}^{(AE)}\otimes \rho^{(Q)}##.

Given the above, can anyone provide an explanation to the following statement which appears in a quantum information theory paper: "Coherences between different measurement outcomes do not remain in the joint state of systems A (apparatus) and Q (quantum system to measured). Any such coherences have “leaked away” into the environment during the dynamical evolution. The pointer states are in fact determined by the requirement that different measurement outcomes decohere via interaction with the environment. "

Thanks for any assistance.
 
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Johny Boy said:
can anyone provide an explanation to the following statement which appears in a quantum information theory paper:
Please please please provide a link to the paper. You will get better answers that way.
 
@Nugatory Okay will do. The PDF of the referenced paper can be found here. Question refers to statement on page 6.
 

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