Photon-Atom Granularity Noise Thermometry

TL;DR

This paper introduces granularity noise thermometry (GNT), a novel optical thermometry method leveraging atomic fluctuations to measure temperature through excess noise in transmitted light.

Contribution

The paper develops a new fluctuation-based optical thermometry scheme that uses atomic susceptibility fluctuations and derives analytical expressions for temperature scaling.

Findings

Excess noise scales linearly with photon-to-atom ratio, enabling temperature measurement.

Derived closed-form expressions for susceptibility moments using plasma dispersion function.

Different temperature scalings identified for thermal vapors and cold atoms.

Abstract

We propose granularity noise thermometry (GNT), a fluctuation-based optical thermometry scheme that exploits the intrinsic fluctuations of susceptibility arising from atomic discreteness. The power spectral density of transmitted light exhibits an excess noise above the shot-noise limit that scales linearly with the photon-to-atom ratio $\mathcal{R}$. Consequently, varying the incident power (hence $\mathcal{R}$) yields the slope $\mathcal{K}$ of this linear scaling, which directly encodes the temperature. Closed-form expressions for the polarizability moments are derived via the plasma dispersion function, which yield distinct temperature scalings: $\mathcal{K}\propto P_{\mathrm{v}}(T)/T^2$ for thermal vapors and $\mathcal{K}\propto T^{2}$ for cold atoms. While practical implementation requires careful control of technical noise and system parameters, the present framework provides a noise-based pathway for optical thermometry using atomic ensembles.