English

Improving the loss threshold for quantum advantage in photonic sensors by complete photon counting

Quantum Physics 2026-06-29 v1

Abstract

Tolerance to imperfections is a defining performance criterion for quantum sensors. The threshold for achieving a quantum advantage depends on the input state, sensor configuration, detection scheme, and, critically for optical platforms, photon loss. We consider a nonlinear interferometer in which two gain-optimized parametric nonlinear optical processes couple the state to the internal sensor and subsequently mix the reference and sensor beams. We demonstrate that measuring the full photon-number output statistics of this setup yields marked improvements in the loss threshold. Using photon-number-resolving detection (PNRD) based on transition-edge sensors (TESs), we experimentally reconstruct the joint photon-number statistics at the interferometer output. Subject to internal and external losses of approximately 25 % and 45 %, respectively -- and without any post-selection or loss correction -- we observe an unconditional violation of the shot-noise limit by 2.37±0.112.37 \pm 0.11 dB. This translates to a 44 % enhancement in estimation precision over conventional click-detection strategies. We verify this performance by evaluating the classical Fisher information against both an analytical model of the joint photon-number distribution and the raw measured statistics. Ultimately, our results demonstrate that combining nonlinear interferometry with PNRD unlocks metrological information fundamentally inaccessible to click detectors, establishing a clear path toward practical, quantum-enhanced sensing under realistic loss conditions.

Keywords

Cite

@article{arxiv.2606.30761,
  title  = {Improving the loss threshold for quantum advantage in photonic sensors by complete photon counting},
  author = {Gerard J. Machado and Yazeed K. Alwehaibi and Guillaume Thekkadath and Zhenghao Li and Aonan Zhang and Shang Yu and Adriana E. Lita and Richard P. Mirin and Martin J. Stevens and Juan P. Torres and Raj B. Patel and Ian A. Walmsley},
  journal= {arXiv preprint arXiv:2606.30761},
  year   = {2026}
}

Comments

11 pages, 3 figures