Rydberg Atoms for Blackbody Sensing and Quantum Thermometry

A ubiquitous source of incoherent radiation is blackbody radiation (BBR), described quantitatively less than two centuries ago to specify thermal bodies. It therefore follows that characterizing BBR is an appropriate technique to accurately assess the temperature of a distant entity. Classical thermal radiation detectors suffer from a number of systematic sources of error and long traceability chains. A thermal radiation detector integrating an invariable quantum system clearly represents the next technological leap in radiation thermometry while being directly traceable to the new International System (SI) of units. Rydberg atoms are a natural tool to use in electrometry as radiation sensors due to their enhanced physical properties. Efforts are underway at NIST to use Rydberg atoms as calibration-free, SI-traceable sensors of thermal radiation, thereby characterizing reference blackbodies at the 100 ppm level¹ and greatly reducing the calibration uncertainty for classical thermal radiation sensors. Furthermore, this sensor may serve to reduce the Stark shift uncertainty in atomic clocks due to BBR, the largest systematic error in those systems to date. Realizing the kelvin in this manner requires merging a vapor cell and appropriate laser systems to observe blackbody-induced transitions through selective-field ionization or fluorescence measurements.

¹E.B. Norrgard, S.P. Eckel, C.L. Holloway, and E.L. Shirley, “Quantum blackbody thermometry” New Journal of Physics 23, 033037 (2021).