Photon Statistics of Propagating Thermal Microwaves

TL;DR

This paper investigates the photon statistics of propagating thermal microwave fields emitted from a black-body radiator, providing precise measurements and insights into noise characteristics relevant for superconducting quantum circuits.

Contribution

It offers the first detailed quantification of photon number variance in thermal microwave fields using correlation measurements and qubit probes.

Findings

Measured photon number variance for mean photon numbers 0.05 to 1.5

Characterized noise emitted by a Josephson parametric amplifier

Demonstrated precise quantum state characterization techniques

Abstract

In experiments with superconducting quantum circuits, characterizing the photon statistics of propagating microwave fields is a fundamental task. We quantify the $n^{2}\,{+}\,n$ photon number variance of thermal microwave photons emitted from a black-body radiator for mean photon numbers $0.05\,{\lesssim}\,n\,{\lesssim}\,1.5$. We probe the fields using either correlation measurements or a transmon qubit coupled to a microwave resonator. Our experiments provide a precise quantitative characterization of weak microwave states and information on the noise emitted by a Josephson parametric amplifier.