What are pure and mixed states in quantum mechanics?

[aveline de grandpre]

what does it mean that a particle is a pure eigenstate?
could someone explain this to me simply ?

 

[DrClaude]

You'll have to give some context as to where you read that.

 

[bhobba]

what does it mean that a particle is a pure eigenstate?
could someone explain this to me simply ?

I have tried and tried to simply explain it failing every time.

Here is the answer.

States are positive operators of unit trace. States of the form |u><u| are called pure. States of the form ∑ pi |ui><ui| are called mixed. It can be shown all states are pure or mixed. If that is gibberish then sorry its the best I can do - explaining linear algebra in English is impossible.

Thanks
Bill