Entanglement purification via separable superoperators

TL;DR

This paper introduces bounds on entanglement purification protocols by analyzing separable superoperators, providing new upper limits on purification rates and channel capacities in quantum information processing.

Contribution

It establishes a general framework using separable superoperators to derive bounds on entanglement purification and channel capacities, simplifying and extending previous results.

Findings

Derived a new upper bound on EPP rates for Bell-diagonal states

Established bounds on the capacity of Bell-diagonal channels

Showed that all EPPs are encompassed by separable superoperator analysis

Abstract

One of the fundamental concepts of quantum information theory is that of entanglement purification; that is, the transformation of a partially entangled state into a smaller-dimensional, more completely entangled state. Of particular interest are protocols for entanglement purification (EPPs) that alternate purely local operations with one- or two-way classical communication. In the present work, we consider a more general, but simpler, class of transformations, called separable superoperators. Since every EPP is a separable superoperator, bounds on separable superoperators apply as well to EPPs; we use this fact to give a new upper bound on the rate of EPPs on Bell-diagonal states, and thus on the capacity of Bell-diagonal channels.