- #1
- 8,943
- 2,948
I don't want to argue about whether the notion of "wave function collapse" is a good way of understanding quantum mechanics, or not. For the purposes of this discussion, let's just adopt uncritically the naive approach to quantum mechanics, that:
My question is: how is the entropy of a system affected by measurement? There is a sense in which it acts like a random perturbation, and so I would think that it would increase the entropy, but on the other hand, the state becomes more definite after a measurement, which would make me think that the entropy has been lowered.
Does my question make any sense, and if so, does it have a standard answer?
- Between measurements, the system evolves according to Schrodinger's equation.
- A measurement always produces an eigenvalue of the operator corresponding to the quantity being measured.
- Immediately after a measurement, the wavefunction "collapses" to an eigenstate of that operator corresponding to the eigenvalue that you measured.
My question is: how is the entropy of a system affected by measurement? There is a sense in which it acts like a random perturbation, and so I would think that it would increase the entropy, but on the other hand, the state becomes more definite after a measurement, which would make me think that the entropy has been lowered.
Does my question make any sense, and if so, does it have a standard answer?