Exploring the boundary of quantum correlations with a time-domain optical processor
Zhenghao Liu, Yu Meng, Yu-Ze Wu, Ze-Yan Hao, Zhen‐Peng Xu, Cheng-Jun Ai, Hai Jun Wei, Kai Wen, Jing‐Ling Chen, Jie Ma, Jin‐Shi Xu, Chuan‐Feng Li, Guang‐Can Guo · Science Advances · 2025
Contextuality is a hallmark feature of the quantum theory that captures its incompatibility with any noncontextual hidden-variable model. The Greenberger-Horne-Zeilinger (GHZ)-type paradoxes are proofs of contextuality that reveal this incompatibility with deterministic logical arguments. However, the GHZ-type paradox whose events can be included in the fewest contexts and that brings the strongest nonclassicality remains elusive. Here, we derive a GHZ-type paradox with a context-cover number of 3 and show that this number saturates the lower bound posed by quantum theory. We demonstrate the paradox with a time-domain fiber optical platform and recover the quantum prediction in a 37-dimensional setup based on high-speed modulation, convolution, and homodyne detection of time-multiplexed pulsed coherent light. By proposing and studying a strong form of contextuality in high-dimensional Hilbert space, our results pave the way for the exploration of exotic quantum correlations with time-multiplexed optical systems.