Visibility-Engineered Multiparameter Sensing in Dispersive Quantum Interferometry: Identifiability, Noise Robustness, and Hardware Emulation
We propose a dispersive interferometric protocol for simultaneously estimating the dimensionless inverse temperature $b=β\hbarω_0$ of a thermal two-level ancilla and the dispersive phase $x=χt/2$. Photon counting at the interferometer output yields probabilities governed by the fringe visibility $\mathcal{V}(b)$; its magnitude controls phase sensitivity, while its derivative sets thermometric sensitivity. A single binary outcome provides only a rank-one Fisher matrix, so local identifiability requires combining several controlled reference phases. We build a multi-setting likelihood and numerically demonstrate that a maximum-likelihood estimator attains the Cramér--Rao bound asymptotically. For $N=1$ we implement the equivalent qubit circuit on IBM Quantum hardware, interpreting the data as a conservative likelihood emulation; the observed contrast shrinkage is consistent with a noise bias toward infinite temperature. We also compare NOON, cat, and squeezed probe states under amplitude and phase damping, highlighting windows of usable joint sensitivity. The framework clarifies what can be inferred from photon counting statistics and which control settings are necessary for genuine multiparameter estimation in realistic platforms.