Photon-Pair Advantage for Dissipative Parameter Estimation in Whispering-Gallery-Mode Interferometers

arXiv:2610.32541v1 Announce Type: new Abstract: We study the estimation of detuning and intrinsic loss in a lossy whispering-gallery-mode (WGM) resonator located in a balanced Mach--Zehnder interferometer. We use indistinguishable photon pairs and coherent-state probes. We show that using indistinguishable photon pairs can provide higher Quantum Fisher Information (QFI) of dissipative parameters, such as intrinsic loss, at resonance away from critical coupling. Taking into account all photon-loss outcomes, we obtain analytical QFI expressions and compare photon-pair and coherent-state probe results when they have the same mean photon number.