Adaptive versus non-adaptive strategies for quantum channel discrimination

TL;DR

This paper demonstrates that adaptive strategies can perfectly discriminate certain quantum channels with fewer evaluations than any non-adaptive approach, highlighting the advantage of adaptivity in quantum channel discrimination.

Contribution

The paper provides a simple example showing the superiority of adaptive strategies over non-adaptive ones in quantum channel discrimination, especially for entanglement-breaking channels.

Findings

Adaptive strategy achieves perfect discrimination with two evaluations.

No finite non-adaptive strategy can perfectly discriminate the channels.

Adaptive methods outperform non-adaptive methods in this quantum task.

Abstract

We provide a simple example that illustrates the advantage of adaptive over non-adaptive strategies for quantum channel discrimination. In particular, we give a pair of entanglement-breaking channels that can be perfectly discriminated by means of an adaptive strategy that requires just two channel evaluations, but for which no non-adaptive strategy can give a perfect discrimination using any finite number of channel evaluations.