B Re-Preparing vs Perturbing Quantum States: Understanding the Difference

[bluecap]

Hi, what is the difference between re-preparing and perturbing a quantum state? I know re-preparing has to do with isolating it from environment and seeing interference effect. What about perturbing it?

 

[PeterDonis]

I know re-preparing has to do with isolating it from environment and seeing interference effect.

Where do you know this from? What reference?

 

[bluecap]

Where do you know this from? What reference?

Reference? I saw you said in one of the old archives "To be able to "re-prepare" a piece of wood, you would have to first isolate it from its environment, and then control all the interactions between its quantum building blocks with sufficient accuracy to allow quantum interference effects to be observable. In principle that could be done, but in practice it is impossible.". So what does it mean to perturb a quantum state? What does perturb mean in standard usage? Isn't perturb same meaning as re-prepare?

 

[PeterDonis]

I saw you said in one of the old archives "To be able to "re-prepare" a piece of wood

Yes, and I put "re-prepare" in quotes because I was speaking heuristically. Plus, IIRC, the term wasn't mine; it was originally used by you in that thread, and I only used it because you did. So what did you mean by it?

what does it mean to perturb a quantum state?

As it stands, this question can't be answered because it's too vague; "perturb" has multiple possible meanings. You would have to give a specific scenario and a specific reference (a textbook or peer-reviewed paper) where the term "perturb" is used.

The questions you are asking are much too general, and also are not really answerable at the "B" level, beyond the heuristic stuff I said in that prior thread. You really, really, really need to take the time to study QM from a good textbook (Ballentine, for example). As it is, I am closing this thread.