Layman's question on Quantum decoherence

In summary, the electron needs a large scale human readable detector in order to interact with the environment.
  • #1
cdux
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Why doesn't it occur constantly and only when 'interacting" with another larger scale phase space? Why does an electron for example require a large scale human readable detector in the way to interact that way with the environment when the environment is there anyway? Air, Dust, etc.
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Also, how can decoherence be 'delayed' as in the more complex eraser experiments?
 
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  • #2
Practically, the electron decoherences, as it encounters a grain of dust. Or, as it ionises some air molecule, while traveling through Wilson's chamber.

Of course, the decoherence may be delayed. As much as you want, as long the information do not reach your, solipsistic mind. Cat did not decorenced the experiment. It was Schrödinger, who had to spot dead cat, to conclude decoherence.
 
  • #3
xts said:
As much as you want, as long the information do not reach your, solipsistic mind. Cat did not decorenced the experiment. It was Schrödinger, who had to spot dead cat, to conclude decoherence.
I don't think that's correct. The world doesn't depend on humans' existence.
 
  • #4
Decoherence or collapse is not something really happening in the world. They are just measures of our knowledge about the world state. From cat's perspective decohernece/collapse occurs when the machine emits either poison or whiskas. From Schrödinger's perspective it occurs when he opens a cage.

You can't say that some wavefunction is collapsed or not in the same meaning, as you may say, that glass of water is liquid or frozen. That's not a property which may be checked if it happened or not. It is just a mental construct, allowing us to simplify further calculations.
 
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  • #5
xts said:
not something really happening in the world.
This is according to many sources outright incorrect.
 
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  • #6
OK. So let me repeat:

'practically' (and that is the most common understanding) decoherence occurs, when something thermodinamically irreversible happens (drop in Wilson's chamber forms around ionised molecule).

'philosophically' - you may defer it as far as you like. Calculations (if you are able to perform them) in the views:
- decoherenced state + classical apparatus;
- entangled state of your particle and apparatus.
lead to the same result.
If your detector (apparatus) is very simple (e.g. it is single electron scattered by the photon you measure) - the second approach is also feasible computationally.
 
  • #7
cdux said:
It does not make any sense to suggest half the nature of Quantum Mechanics requires an observer.
Oh! You should tell it to Niels Bohr!
Nature of the world probably does not require an observer. Nature of QM, which is just a description of the world behaviour, also doesn't. But any particular calculations require some edge assumptions, which are based on experimentalist's knowledge about the world. Collapse is just a trick in computations, elliminating all those previously possible branches of further evolutions, which may be excluded using the knowledge we just possesed.
 
  • #8
Decoherence is different from collapse. Decoherence rejects collapse and explains it as something that creates the appearance of collapse.
 
  • #9
cdux said:
Decoherence is different from collapse. Decoherence rejects collapse and explains it as something that creates the appearance of collapse.
Uuuch? May you elaborate on it a little bit, please!

If you mean 'decoherence' as in Żurek's "DECOHERENCE, EINSELECTION, AND THE QUANTUM ORIGINS OF THE CLASSICAL" http://arxiv.org/abs/quant-ph/0105127v3
that is just what I said: decoherence occurs when our state goes entangled with so many other elements of the world, that:
1. it becomes unfeasible to track those entanglements in QM calculations;
2. they are thermodynamically irreversible .
3. Thus: the approach of 'collapse' is an only feasible (and statistically valid) way to continue with our model.

The electron (leaving visible track) in a Wilson's chamber is a good example of such practical, "real", and feasible approach.
 
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What is quantum decoherence?

Quantum decoherence is a process in which a quantum system interacts with its environment, causing the system to lose its quantum properties and behave classically. This results in the loss of quantum coherence, meaning that the system is no longer in a superposition of states, but instead in a definite state.

Why is quantum decoherence important?

Quantum decoherence is important because it explains why we do not observe quantum effects on a macroscopic scale. It also plays a crucial role in the development of quantum technologies, as it is necessary for maintaining the stability of quantum systems.

How does quantum decoherence occur?

Quantum decoherence occurs when a quantum system interacts with its environment, causing the system to become entangled with the environment's degrees of freedom. This interaction leads to the loss of quantum coherence and the emergence of classical behavior.

What are the consequences of quantum decoherence?

The consequences of quantum decoherence include the loss of quantum superposition and the emergence of classical behavior. It also limits the potential applications of quantum technologies, as maintaining quantum coherence is crucial for their operation.

Can quantum decoherence be prevented?

While it is not possible to completely prevent quantum decoherence, strategies such as quantum error correction and quantum control techniques can help mitigate its effects. Additionally, research is being conducted on materials and systems that are less susceptible to decoherence.

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