Experimental Tomographic State Reconstruction of Itinerant Microwave Photons

TL;DR

This paper demonstrates a method for reconstructing the quantum state of itinerant microwave photons using linear amplifiers and quadrature detection, advancing the study of propagating microwaves in quantum optics.

Contribution

It introduces an efficient technique to reconstruct the Wigner function of itinerant microwave photons, including superpositions, from noisy measurements.

Findings

Successfully reconstructed Wigner functions of single photon states.

Developed a method to separate signal from amplifier noise.

Enabled new studies of propagating microwave quantum states.

Abstract

A wide range of experiments studying microwave photons localized in superconducting cavities have made important contributions to our understanding of the quantum properties of radiation. Propagating microwave photons, however, have so far been studied much less intensely. Here we present measurements in which we reconstruct the Wigner function of itinerant single photon Fock states and their superposition with the vacuum using linear amplifiers and quadrature amplitude detectors. We have developed efficient methods to separate the detected single photon signal from the noise added by the amplifier by analyzing the moments of the measured amplitude distribution up to 4th order. This work is expected to enable studies of propagating microwaves in the context of linear quantum optics.