Sub-shot-noise transmission measurement using optically gated single photons

TL;DR

This paper demonstrates a quantum-enhanced transmission measurement technique using optically gated single photons, achieving improved precision over classical methods by reducing detector efficiency requirements.

Contribution

It introduces a feed-forward configuration with an optical switch and delay, enabling quantum advantage in transmission measurement at lower detection efficiencies.

Findings

Achieved a 1.27-fold improvement in transmission measurement precision.

Quantum advantage observed only when the optical switch is active.

Method reduces the detector efficiency threshold for quantum-enhanced sensing.

Abstract

Harnessing the unique properties of quantum mechanics offers the possibility to deliver new technologies that can fundamentally outperform their classical counterparts. These technologies only deliver advantages when components operate with performance beyond specific thresholds. For optical quantum metrology, the biggest challenge that impacts on performance thresholds is optical loss. Here we demonstrate how including an optical delay and an optical switch in a feed-forward configuration with a stable and efficient correlated photon pair source reduces the detector efficiency required to enable quantum enhanced sensing down to the detection level of single photons. When the switch is active, we observe a factor of improvement in precision of 1.27 for transmission measurement on a per input photon basis, compared to the performance of a laser emitting an ideal coherent state and measured with the same detection efficiency as our setup. When the switch is inoperative, we observe no quantum advantage.