While significant work has been done in understanding how non-classical optical probes and enhance our ability to measure and detect loss in a channel, far less has been done about measuring gain. Here we focus on Phase-insensitive optical amplifiers that amplify input light-beams in a way that is phase-independent.
We showed that unlike in the measures of loss, the average quantity of light introduced (referred to as the "photon number N") and the count of different pathways or 'modes' that light can follow ("input modes M") are equally effective for accurately measuring the gain. We also found that specific types of probes hat enable optimal performance. Our findings demonstrate that these quantum probes can measure with higher precision than conventional light, even under the conditions of using single-photon probes and imperfect photodetection method.
- Optimal Gain Sensing of Quantum-Limited Phase-Insensitive Amplifiers
Ranjith Nair, Guo Yao Tham, and Mile Gu, Phys. Rev. Lett. 128, 180506
