Decoherence of measurement outcomes

In summary, the conversation discusses a quantum system with an initial state and a measurement process involving two additional quantum systems. The statement in question from a quantum information theory paper suggests that any coherences between different measurement outcomes in the joint state of the apparatus and quantum system have leaked into the environment during the dynamical evolution. The pointer states, which determine different measurement outcomes, are influenced by the interaction with the environment.
  • #1
Johny Boy
10
0
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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  • #2
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.
 
  • #3
@Nugatory Okay will do. The PDF of the referenced paper can be found here. Question refers to statement on page 6.
 

1. What is decoherence of measurement outcomes?

Decoherence of measurement outcomes refers to the process by which the quantum state of a system becomes entangled with the environment, leading to a loss of coherence and the emergence of classical behavior. This is a fundamental concept in quantum mechanics that explains why macroscopic objects appear to follow classical laws of physics.

2. How does decoherence occur?

Decoherence occurs when a quantum system interacts with its environment, causing the system's wavefunction to become entangled with the environment's degrees of freedom. This leads to a loss of information about the system's quantum state, making it appear classical. The speed at which decoherence occurs depends on the strength of the system-environment interaction and the size of the system.

3. What are the consequences of decoherence?

The consequences of decoherence include the emergence of classical behavior in macroscopic objects, the loss of quantum interference effects, and the inability to observe superposition states. Decoherence also plays a crucial role in the measurement process, as it explains how a definite measurement outcome is obtained from a superposition of states.

4. Can decoherence be controlled?

Decoherence is a natural process that cannot be completely controlled. However, it can be mitigated through techniques such as quantum error correction and quantum error avoidance. These methods aim to reduce the effects of decoherence and maintain the coherence of a quantum system for a longer period of time.

5. Why is decoherence important in quantum computing?

Decoherence is a major challenge in quantum computing as it limits the ability to maintain quantum coherence in a system. This makes it difficult to perform complex quantum operations and increases the chances of errors in quantum computations. Therefore, understanding and controlling decoherence is crucial for the development and scalability of quantum computers.

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