I What is an observable exactly?

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What is an observable exactly? I hear terms that are used in physics books like an observable or a detection. What types of equipment do physicists use to make all these quantum measurements that are used in books so frequently? How small of a region of space does the wave function "collapse" into when measuring particles?
 
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dsaun777 said:
How small of a region of space does the wave function "collapse" into when measuring particles?
Whether wave function collapse happens at all is an open question (different interpretations of quantum mechanics say different things on this topic).
 
dsaun777 said:
What types of equipment do physicists use to make all these quantum measurements that are used in books so frequently?
One example of equipment is photodetectors. But there are other types of equipment used, depending on what is studied. Examples of additional equipment: magnets, polarizers, waveplates etc.
 
Technically, an observable is just a Hermitian operator on whatever Hilbert space you're working in.
 
Not an expert in QM. AFAIK, Schrödinger's equation is quite different from the classical wave equation. The former is an equation for the dynamics of the state of a (quantum?) system, the latter is an equation for the dynamics of a (classical) degree of freedom. As a matter of fact, Schrödinger's equation is first order in time derivatives, while the classical wave equation is second order. But, AFAIK, Schrödinger's equation is a wave equation; only its interpretation makes it non-classical...
I am not sure if this falls under classical physics or quantum physics or somewhere else (so feel free to put it in the right section), but is there any micro state of the universe one can think of which if evolved under the current laws of nature, inevitably results in outcomes such as a table levitating? That example is just a random one I decided to choose but I'm really asking about any event that would seem like a "miracle" to the ordinary person (i.e. any event that doesn't seem to...

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