Practical Advantage of Classical Communication in Entanglement Detection.

Abstract

Entanglement is the cornerstone of quantum communication, yet conventional detection relies solely on local measurements. In this Letter, we present an experimental demonstration, based on an improved theoretical framework showing that one-way local operations and classical communication (1-LOCC) can significantly outperform purely local measurements in detecting quantum entanglement. By casting the entanglement detection problem as a semidefinite program, we derive protocols that minimize false negatives at fixed false-positive rates. A variational generative machine-learning algorithm efficiently searches over high-dimensional parameter spaces, identifying states and measurement strategies that exhibit a clear 1-LOCC advantage. Experimentally, we realize a genuine event-ready protocol on a three-dimensional photonic entanglement source, employing fiber delays as short-lived quantum memories. We implement rapid, field-programmable gate array-based sampling of the optimized probabilistic instructions, allowing Bob's measurement settings to adapt to Alice's outcomes in real time. Our results validate the predicted 1-LOCC advantage in a realistic noisy setting and reduce the experimental trials needed to certify entanglement. These findings mark a step toward scalable, adaptive entanglement detection methods crucial for quantum networks and computing, paving the way for more efficient generation and verification of high-dimensional entangled states.