Entanglement Detection with Variational Quantum Interference: Theory and Experiment

Entanglement detection is a fundamental task in quantum information science, serving as a cornerstone for quantum benchmarking and foundational studies. With an increasing qubit number that can be effectively controlled, there is a pressing need for a scalable and robust detection protocol which requires minimal resources while maintaining high detection capability. By integrating the Positive Partial Transposition criterion with variational quantum interference, we propose an entanglement detection protocol that requires moderate classical and quantum computation resources. We numerically show that this protocol achieves a high detection capability with shallow quantum circuits, surpassing some widely-used entanglement detection methods. The protocol also exhibits strong resilience to circuit noise, ensuring its applicability across different physical platforms. We further demonstrate the protocol experimentally on an eight-photon linear-optical platform, where it successfully detects the entanglement of a three-qubit mixed state that is inaccessible to conventional entanglement witnesses. By combining quantum interference with classical optimization, our protocol provides a scalable and resource-efficient route toward practical entanglement detection.