Mixture of multiple copies of maximally entangled states is quasipure
Dong Yang, Yixin Chen · Physical Review A · 2004
Employing the general bilateral controlled-NOT operation and local state discrimination, the mixed state of the form ${\ensuremath{\rho}}_{d}^{(k)}{=(1/d}^{2}){\ensuremath{\sum}}_{m,n=0}^{d\ensuremath{-}1}(|{\ensuremath{\varphi}}_{\mathrm{mn}}〉〈{\ensuremath{\varphi}}_{\mathrm{mn}}|{)}^{\ensuremath{\bigotimes}k}$ is proved to be quasipure, where ${|{\ensuremath{\varphi}}_{\mathrm{mn}}〉}$ is the canonical set of mutually orthogonal maximally entangled states in $d\ifmmode\times\else\texttimes\fi{}d.$ Therefore irreversibility does not occur in the process of distillation for this family of states. Also, the distillable entanglement is calculated explicitly.