Decoherence. Does it solve the measurement problem? Is it discontinuous? When does it occur?
I am trying to better understand the current scientific consensus (to the extent that such a thing exists) on the interpretation of quantum physics. I understand that this is still very much an active area of research but it seems to me that there is a general belief that decoherence is some sort of holy grail?
When I first was introduced to QT we were taught around the formalism of the Copenhagen interpretation (vague and unsatisfactory concepts of observations/measurements with a totally arbitrary line-in-the-sand between quantum and classical) and it was my understanding that the so called, "Measurement Problem" was still one of the big unsolved problems in physics. More recently however, I have gained the impression that a lot of people regard decoherence as the solution to this problem, but I have also seen specific claims that decoeherence does not attempt to resolve the measurement problem at all. Which is it? Is the measurement problem still a thing?
2 bonus questions!
1. It is my understanding that decoherence is a gradual process? Something that occurs quite rapidly but not instantaneously (correct?). 651
So then, what does this have to say about the old notion of the discontinuous "qauntum leap"? Does the mainstream physics community still regard this "collapse" process as a discontinuous thing or is my understanding out of date?
2. This may not be worded correctly but here goes... When does decoherence occur? Take for example the double-slit experiment, if "collapse" occurs before the two waves interfere, then there will be no interference pattern. If "collapse" occurs after interference then there will be an interference pattern. This tell me that the process of "collapse" has a definite time of occurrence. So then, why does it happen when it does? What is preventing decoherence from occurring before the particle/wave passes through the slits? What is so different about a "measurement apparatus" compared to a molecule of nitrogen in the air or some other such thing? If I am to believe that it's simply a matter of having a large number of hidden degrees of freedom then where do you draw the line? Precisely how many free particles does an object need to have before we call it a "classical" object?! 400