Physical mechanism for decoherence?

In summary, decoherence is a process that eliminates the quantum coherence between macroscopically distinct components of a system's state. It occurs due to the interactions between the system and its environment, and is used to explain the particular branching that occurs in the many-worlds interpretation of quantum mechanics.
  • #1
billy_boy_999
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i know very little quantum mechanics and would appreciate as qualitative a reply as anyone can muster...

what is the physical mechanism for decoherence? decoherence sounds like a solution to quantum 'weirdness' if i understand it correctly...you have to take into account a myriad quantum systems interacting with each other and this somehow jolts the quantum system back into something like a classical behaviour? but what is the mechanism for this jolting into classical mechanics? what physical process cancels out the ambiguity of the wave function?
 
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  • #2
Systems interact with their environment via Hamiltonians that naturally interact differently with components of the quantum state that are "macroscopically" different. For example, components which have vastly different energy or position, or the dead and alive components of Schroedinger's famous cat. Ususally, we do not have full information or control of the environment, so we must find a way of describing the state of the system without including all the environmental degress of freedom. If we do this, it turns out that all the quantum coherence between macroscopically distinct components of the state becomes washed out by the interactions with the environment. Thus, we are left with a state that looks a lot more like a classical mixture of possibilities than a quantum superposition.

Some would argue that this is all there is to be said about the reduction of quantum mechanics to classical physics for macroscopic systems. They claim that it solves the measurement problem and related paradoxes. However, note that we still have a quantum superposition if we take the entire system, including the environment, into account. Thus, I think that the appropriate way to view decoherence is as a tool to explain the particular branching that occurs in the many-worlds interpretation. However, this interpretation still has other difficulties, such as the meaning of probability, so it is inapropriate to say that decoherence has solved all the difficulties of quantum mechanics at this point.
 
  • #3
Review paper on Decoherence

For anyone interested in decoherence, there is a recent review paper by M. Schlosshauer: Decoherence, the Measurement Problem, and Interpretations of Quantum Mechanics. A preprint is available at http://arxiv.org/abs/quant-ph/0312059.

It was only recently brought to my attention, so I haven't read it yet.
 
  • #4


Here's a paper written by the famous Leonard Susskind as his way of dealing with the probability issue that slyboy brought up.
http://arxiv.org/abs/1105.3796
 

1. What is decoherence?

Decoherence is a physical process that occurs in quantum systems when they interact with their environment. It causes the quantum properties of the system to become mixed with the environment, leading to loss of coherence and the system behaving classically.

2. What is the role of decoherence in quantum mechanics?

Decoherence plays a crucial role in explaining how quantum systems appear to behave classically. It is responsible for the collapse of the wave function and is necessary for the emergence of classical behavior from quantum systems.

3. What is the physical mechanism for decoherence?

The physical mechanism for decoherence is the interaction of the quantum system with its environment. This interaction causes the quantum properties of the system to become entangled with the environment, resulting in loss of coherence and the appearance of classical behavior.

4. How does decoherence affect quantum computers?

Decoherence is a major challenge for quantum computing because it can cause errors and loss of information in quantum systems. To minimize the effects of decoherence, researchers are developing techniques such as error correction and fault-tolerant quantum computing.

5. Can decoherence be reversed?

Decoherence is a natural and irreversible process, but it can be mitigated by controlling the environment and the system's interactions with it. Researchers are also exploring ways to manipulate and control the quantum state to reverse or minimize the effects of decoherence.

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