Einstein-Podolsky-Rosen steering provides the advantage in entanglement-assisted subchannel discrimination with one-way measurements

TL;DR

This paper demonstrates that Einstein-Podolsky-Rosen steering enables a quantum advantage in subchannel discrimination tasks with one-way measurements, and this advantage is quantitatively linked to the steerability measure called steering robustness.

Contribution

It provides a necessary and sufficient characterization of steering in quantum information processing, linking it to practical advantages in subchannel discrimination with one-way measurements.

Findings

Steerable states outperform unsteerable states in subchannel discrimination.

The steering advantage is quantified by the steering robustness measure.

Unsteerable states do not provide any advantage in the task.

Abstract

Steering is the entanglement-based quantum effect that embodies the "spooky action at a distance" disliked by Einstein and scrutinized by Einstein, Podolsky, and Rosen. Here we provide a necessary and sufficient characterization of steering, based on a quantum information processing task: the discrimination of branches in a quantum evolution, which we dub subchannel discrimination. We prove that, for any bipartite steerable state, there are instances of the quantum subchannel discrimination problem for which this state allows a correct discrimination with strictly higher probability than in absence of entanglement, even when measurements are restricted to local measurements aided by one-way communication. On the other hand, unsteerable states are useless in such conditions, even when entangled. We also prove that the above steering advantage can be exactly quantified in terms of the steering robustness, which is a natural measure of the steerability exhibited by the state.