Does the environment cause wave function collapse

[bhobba]

Well there is a distinction between decoherence and a particle going into an Eigenstate right? So what physical act makes the distinction between simply limiting the probability of the possible paths a particle travels versus collapsing it into a single outcome?

Do you mean the distinction between apparent collapse and real collapse? If so that has been discussed innumerable times on this forum - do a search for the gory detail. But basically there is no way to tell the difference between apparent collapse and real collapse.

Say, in the double slit experiment, you put a device to detect a particle going through a slit. This means you get, at the slits, an interaction between the detector and photon that changes it to an improper mixed state so it now has an actual probability of going through one slit or the other - coherence has been destroyed and you do not get an interference effect.

Can I ask you to be a bit more precise in your questions - I am finding it a bit difficult figuring out what exactly you are asking.

Thanks
Bill

 

[kith]

Traditional textbooks suggest that we have two types of interactions: unitary interactions and measurement interactions. Because in modern approaches, the latter are explained by the first via decoherence (at least to a certain degree) many people use "decoherence" and "measurement" interchangeably. I don't think this is good practice. I prefer the everyday meaning of "measurement" which involves an observer somehow. Using this terminology, decoherence occurs in all measurements, but not every decoherence process corresponds to a measurement.

Of course if you set up an apparatus to observe the outcome in that pointer basis it will give a result consistent with it having collapsed [...]

You don't have a pointer basis without the apparatus because the pointer is part of the apparatus.

 

[bhobba]

You don't have a pointer basis without the apparatus because the pointer is part of the apparatus.

Not necessarily. Usually the inverse square (or some power of distance) like nature of interactions singles out position as the pointer basis. You will find a discussion of this on page 83 of Schlosshauer - Decoherence And The Quantum To Classical Transition. The ubiquitous nature of these types of interactions is why objects are usually decohered to have positions.

Thanks
Bill

 

[kith]

I don't disagree that a basis of the system is singled out.

I thought that the expression "pointer basis" would refer to -well- the pointer of the measurement apparatus and not the system itself. But you are right, Schlosshauer doesn't make this distinction and his usage seems to be common. My background regarding decoherence is the theory of open quantum systems where the concept of measurements is not important. So the terminology used by foundations people like Schlosshauer is not my mother tongue. Thanks for clarifying!

off topic: I remember that you said that Schlosshauer doesn't mention the factorization problem. I just skimmed a few chapters and he does comment on it in section 2.14, although very briefly. I don't know if this is news to you, I just thought I'd mention it.

 

[bhobba]

I remember that you said that Schlosshauer doesn't mention the factorization problem. I just skimmed a few chapters and he does comment on it in section 2.14, although very briefly. I don't know if this is news to you, I just thought I'd mention it.

Just read it.

He does indeed - well picked up.

Thanks
Bill