But there is a problem. The definition of “quantum eigenstate” seems to be circular: 

an eigenstate = a definite state = a classical state

a quantum eigenstate = a microscopic state corresponding to a macroscopic (classical) state

The phrase “quantum eigenstates” is defined in terms of “classical states”. However, classical states exist only because of the decoherence of quantum states of a lot of particles. The universe is fundamentally quantum, not classical. The classical world exists only as an approximation to the quantum universe.

Also, we cannot define a quantum eigenstate as a collapsed quantum state, because in reality, there is no wave function collapse. Collapse is only an illusion due to quantum decoherence.

So, after all, what is the meaning of “a quantum eigenstate”?

— Me@2013.06.18

2013.06.18 Tuesday (c) All rights reserved by ACHK