Characterizing qubit channels in the context of quantum teleportation

TL;DR

This paper analyzes how different qubit channels affect the quality of quantum teleportation, identifying conditions under which channels produce states useful for universal teleportation, especially highlighting the effectiveness of non-unital channels.

Contribution

It characterizes qubit channels based on their ability to produce states suitable for universal quantum teleportation, revealing the advantages of non-unital channels with non-maximally entangled states.

Findings

Non-unital channels can produce useful teleportation states from non-maximally entangled states.

Certain qubit channels enable universal teleportation with zero fidelity deviation.

Non-unital channels outperform unital channels in specific teleportation scenarios.

Abstract

We consider a scenario where a party, say, Alice prepares a pure two-qubit (either maximally entangled or non-maximally entangled) state and sends one half of this state to another distant party, say, Bob through a qubit (either unital or non-unital) channel. Finally, the shared state is used as a teleportation channel. In this scenario, we focus on characterizing the set of qubit channels with respect to the final state's efficacy as a resource of quantum teleportation (QT) in terms of maximal average fidelity and fidelity deviation (fluctuation in fidelity values over the input states). Importantly, we point out the existence of a subset of qubit channels for which the final state becomes useful for universal QT (having maximal average fidelity strictly greater than the classical bound and having zero fidelity deviation) when the initially prepared state is either useful for universal QT (i.e., for a maximally entangled state) or not useful for universal QT (i.e., for a subset of non-maximally entangled pure states). Interestingly, in the latter case, we show that non-unital channels (dissipative interactions) are more effective than unital channels (non-dissipative interactions) in producing useful states for universal QT from non-maximally entangled pure states.