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Optical Fiber Communication Conference

Field demonstration of distributed quantum sensing without post-selection

Si-Ran Zhao, Yuzhe Zhang, Wen‐Zhao Liu, Jian-Yu Guan, Weijun Zhang, Chenglong Li, Bing Bai, Ming-Han Li, Yang Liu, Lixing You, Jun Zhang, Jingyun Fan, Feihu Xu, Qiang Zhang, Jian-Wei Pan

Published Jan 1, 2021• 3 citations
Publisher

Abstract

We demonstrate distributed quantum sensing in field and show the unconditional violation (without post-selection) of shot-noise limit up to 0.916 dB with the averaged heralding efficiency of 73.88% for the field distance of 240 m.
DOI
10.1364/ofc.2021.th4f.3

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The limit of precision in optical measurements is due to quantum fluctuations, which are governed by Poissonian statistics. With a clever setup, however, the authors achieve a precision in transmission measurements that beats this limit, without the selective analysis of recorded data (post-selection). This shows that the single-photon-detector approach, used by many groups worldwide, is viable for real-world optical quantum metrology, not just proof-of-principle tests. In turn, this demonstration unlocks an array of techniques for quantum-state engineering that crucially depend on single-photon detection.
Distributed quantum sensing is an emerging application of quantum networking, where entangled probe states are employed to sense combinations of delocalized parameters with enhanced precision relative to using separable states. Squeezed states of light are a prime resource for experimental demonstrations of entanglement-enhanced sensing, because they can be generated and entangled deterministically. Existing distributed quantum sensing experiments have been fundamentally limited in scalability due to their bulk-optic architectures. Meanwhile, integrated photonics provides a scalable and compact platform for quantum sensors. Here we demonstrate entanglement-enhanced sensing of linear functions of four phase shifts in an integrated photonic circuit. We find an entanglement-enhanced precision of 0.199(16) dB below the shot noise limit compared to 0.041(18) dB for separable states. A four-mode entangled state is generated on-chip with entanglement verification and phase sensing also performed on-chip with an array of four integrated homodyne detectors.