I was researching what eigenstate is and found a good explanation from the web.

An eigenstate is one of the many possible states which may exist prior to quantum decoherence

Ok, I don’t know what quantum decoherence means, but here’s a better analogy.

The story of Schrodinger’s Cat is one of the most well known story involving eigenstates. The story goes like this:

There’s a cat inside a box, with a poison ready to be release anytime. Since you don’t know when the poison is released, the cat is either alive or dead. Alive and dead is the eigenstates.

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