Exploring the boundary of quantum correlations with a time-domain optical processor

TL;DR

This paper derives a new GHZ-type paradox with minimal contexts, demonstrating it experimentally using a high-dimensional, time-multiplexed optical platform, advancing the understanding of quantum contextuality.

Contribution

It introduces a novel GHZ-type paradox with a minimal context-cover number and experimentally verifies it in a high-dimensional optical system.

Findings

Successfully demonstrated the paradox in a 37-dimensional setup

Confirmed the quantum prediction aligns with the derived paradox

Established a new benchmark for contextuality in high-dimensional systems

Abstract

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 which brings the strongest nonclassicality remains elusive. Here, we derive a GHZ-type paradox with a context-cover number of three and show 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.