A resource-efficient and noise-robust entanglement witness based on the swap test
Abstract
Quantum entanglement is an essential resource for quantum technologies, and the controlled swap test provides a versatile tool for its detection and quantification. Here, we propose a SWAP-based entanglement witness that applies to arbitrary two-qubit states - both pure and mixed - and provides a lower bound on the concurrence. The method is resource-efficient, robust to noise, and platform-independent. As an example, we validate the approach on a room-temperature photonic chip, where the swap test is carried out using only linear and well-established integrated optical components. The robustness of the method against photonic-hardware noise is also analysed. Our results establish a simple and reliable tool for entanglement witnessing.
Cite
@article{arxiv.2512.20235,
title = {A resource-efficient and noise-robust entanglement witness based on the swap test},
author = {Sebastiano Guaraldo and Sonia Mazzucchi and Alessio Baldazzi and Stefano Azzini and Lorenzo Pavesi},
journal= {arXiv preprint arXiv:2512.20235},
year = {2025}
}
Comments
34 pages, 6 figures