Primary quantum thermometry of mm-wave blackbody radiation via induced state transfer in Rydberg states of cold atoms

TL;DR

This paper demonstrates a novel, calibration-free quantum thermometer using Rydberg atoms to measure blackbody radiation at 130 GHz with high temperature sensitivity and SI-traceability.

Contribution

It introduces a primary quantum thermometry method based on Rydberg state transfer induced by blackbody radiation, enabling SI-traceable temperature measurements at microwave frequencies.

Findings

Achieved temperature sensitivity of 26 K·Hz$^{-1/2}$ at room temperature.

Demonstrated a systematic fractional temperature uncertainty of 0.006.

Validated the method with a semi-classical population transfer model.

Abstract

Rydberg states of alkali atoms are highly sensitive to electromagnetic radiation in the GHz-to-THz regime because their transitions have large electric dipole moments. Consequently, environmental blackbody radiation (BBR) can couple Rydberg states together at $\mu$s timescales. Here, we track the BBR-induced transfer of a prepared Rydberg state to its neighbors and use the evolution of these state populations to characterize the BBR field at the relevant wavelengths, primarily at 130 GHz. We use selective field ionization readout of Rydberg states with principal quantum number $n\sim30$ in $^{85}$Rb and substantiate our ionization signal with a theoretical model. With this detection method, we measure the associated blackbody-radiation-induced time dynamics of these states, reproduce the results with a simple semi-classical population transfer model, and demonstrate that this measurement is temperature sensitive with a statistical sensitivity to the fractional temperature uncertainty of 0.09 Hz$^{-1/2}$, corresponding to 26 K$\cdot$Hz$^{-1/2}$ at room temperature. This represents a calibration-free SI-traceable temperature measurement, for which we calculate a systematic fractional temperature uncertainty of 0.006, corresponding to 2 K at room temperature when used as a primary temperature standard.