Purity

'''Purity''' is a measure of how pure a [[mixed state|quantum state]] is. It is often used because it is easy to compute. It is defined as $tr(\backslash rho^2)$. The purity is one for [[pure state]]s and $1/d$ for maximally mixed states of dimension $d$. Related to the purity is the [[linear entropy]], which measures the mixedness of a state. [[Category: Stubs]] [[Category: Entropy]]