Quantum mechanical wave function collapse?

Question

Is there any way to tell if a quantum particle is in a definite state or a superposition of states before a measurement is made?

Another words, when you make a measurement, is there any way to know if your measurement collapsed the wavefunction or if it just measured a definite eigenstate that had previously collapsed?

Answer 1

The only way I can think of to tell experimentally is to identically prepare many systems and take many such measurements. If they all come out the same, the system was in an eigenstate. If not, you apparently collapsed it with your measurement.

Of course it isn't hard to prepare a system that you KNOW will or won't be an eigenstate. For example, if you measure the x-component of an electron's spin, you know you can't be in an eigenstate of the y- or z-components.

Answer 2

By making the measurement you cause the wave function to collapse to one of its possible eigenstates (in the classical 'Stockholm' interpretation of QM). There's also the 'Everett' interpretation of QM that says an observation (measurement) represents a bifurcation (in an infinite-dimensional 'multiverse') and that all possible states happen (the information of which propagates through all multiverses at luminal velocity).

Doug

Answer 3

yes ask your self does what i am doing now have anything to do with what i am trying to figure out what it is