Classical Communication Enhanced Quantum State Verification

TL;DR

This paper demonstrates that classical communication in adaptive quantum state verification significantly improves efficiency, reducing measurements needed and approaching the globally optimal bound, thus enhancing quantum device reliability assessment.

Contribution

Introducing classical communication into quantum state verification to experimentally improve efficiency and approach the optimal measurement scaling.

Findings

Constant-factor reduced from ~2.5 to 1.5

Achieved 60% of measurements compared to non-adaptive local strategy

Performance approaches the globally optimal bound

Abstract

Quantum state verification provides an efficient approach to characterize the reliability of quantum devices for generating certain target states. The figure of merit of a specific strategy is the estimated infidelity $\epsilon$ of the tested state to the target state, given a certain number of performed measurements n. Entangled measurements constitute the globally optimal strategy and achieve the scaling that \epsilon is inversely proportional to n. Recent advances show that it is possible to achieve the same scaling simply with non-adaptive local measurements, however, the performance is still worse than the globally optimal bound up to a constant factor. In this work, by introducing classical communication, we experimentally implement an adaptive quantum state verification. The constant-factor is minimized from ~2.5 to 1.5 in this experiment, which means that only 60% measurements are required to achieve a certain value of \epsilon compared to optimal non-adaptive local strategy. Our results indicate that classical communication significantly enhances the performance of quantum state verification, and leads to an efficiency that further approaches the globally optimal bound.