Enhanced quantum hypothesis testing via the interplay between coherent evolution and noises

TL;DR

This paper reveals that, contrary to traditional views, certain noise types can enhance quantum hypothesis testing success probabilities, especially when combined with coherent controls, demonstrated through experimental ultralow-field NMR systems.

Contribution

It establishes conditions where noisy quantum dynamics outperform noiseless evolution in hypothesis testing and demonstrates noise-assisted protocols experimentally.

Findings

Noise can improve QHT success probability beyond noiseless limits.

Strategic coherent controls can turn detrimental noise into an advantage.

Experimental validation in ultralow-field NMR systems confirms theoretical predictions.

Abstract

Previous studies in quantum information have recognized that specific types of noise can encode information in certain applications. However, the role of noise in Quantum Hypothesis Testing (QHT), traditionally assumed to undermine performance and reduce success probability, has not been thoroughly explored. Our study bridges this gap by establishing sufficient conditions for noisy dynamics that can surpass the success probabilities achievable under noiseless (unitary) dynamics within certain time intervals. We then devise and experimentally implement a noise-assisted QHT protocol in the setting of ultralow-field nuclear magnetic resonance spin systems. Our experimental results demonstrate that the success probability of QHT under the noisy dynamics can indeed surpass the ceiling set by unitary evolution alone. Moreover, we have shown that in cases where noise initially hampers the performance, strategic application of coherent controls on the system can transform these previously detrimental noises into advantageous factors. This transformative approach demonstrates the potential to harness and leverage noise in QHT, which pushes the boundaries of QHT and general quantum information processing.