In the thought experiment called Schrodinger's Cat, the cat "is" in one of two conditions -- alive and dead -- and theoretically is in both of them in alternate universes of branching unfolding lines of event. So my guess is that an "eigenstate" from the German word for "special" is a special way of looking at quantum phenomena. I'm building this a bit at a time though... so lemme go chew some more....

....OK, I'm believed to be back. So... if you look at one of this "possible states" in a particular way you get a specific perception of an "outcome" reality, one of the many probability states it could have been in. I THINK the eigenstate is the bundle of all possible probability states that a quantum "thing" could be in. OR an eigenstate is the combination of all possible states PLUS a particular perspective that "projects" the quantum event ONTO its eigenstate so that one outcome is now determined. They talk, for example, about whether a particular measurement is a momentum eigenstate or a location eigenstate, meaning that looking at the quantum event that way projects it into an outcome of one or the other, but not both pieces of information being revealed (this is associated with the Heisenberg Uncertainty Principle, which I know enough to name but not enough to truly explain, dumb me....).

I guess each of the possible state-values of a system before it is measured is also called an Eigenstate. So the cat has two -- the alive eigenstate and the dead eigenstate. But only one of them shows up as actual, and only when the measurement is taken (opening the box). The set of all the states of a quantum system can be represented by a finite-dimensional complex vector space with an inner product. This is the superposition of all the individual eigenstates of a system -- if I understand this tricky concept right. Opening the box "pins" or "projects" the quantum system "cat" onto its eigenstate "dead" or "alive" depending on the instant or other characteristic of the measurement.

Anyone want to reassure me out there?

Regards,

Amos