Classical communication enhanced quantum state verification
Wen-Hao Zhang, Xiao Liu, Peng Yin, Xing-Xiang Peng, Gongchu Li, Xiao-Ye Xu, Shang Yu, Zhibo Hou, Yong‐Jian Han, Jin‐Shi Xu, Zong‐Quan Zhou, Geng Chen, Chuan‐Feng Li, Guang‐Can Guo · npj Quantum Information · 2020
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 ϵ 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 ϵ 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 ϵ 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.