Quantum wave mixing and visualisation of coherent and superposed photonic states in a waveguide

TL;DR

This paper demonstrates quantum wave mixing on a single superconducting artificial atom, visualizing photon states and revealing nonlinear quantum effects in microwave optics.

Contribution

It introduces the first observation of quantum wave mixing on a single artificial atom, visualizing photon-state statistics in the quantum regime.

Findings

Spectrum maps superposed and coherent photonic states

Visualizes photon-state statistics with finite peaks

Reveals nonlinear quantum effects in microwave optics

Abstract

Superconducting quantum systems (artificial atoms) have been recently successfully used to demonstrate on-chip effects of quantum optics with single atoms in the microwave range. In particular, a well-known effect of four-wave mixing could reveal a series of features beyond classical physics, when a non-linear medium is scaled down to a single quantum scatterer. Here we demonstrate a phenomenon of the quantum wave mixing (QWM) on a single superconducting artificial atom. In the QWM, the spectrum of elastically scattered radiation is a direct map of the interacting superposed and coherent photonic states. Moreover, the artificial atom visualises photon-state statistics, distinguishing coherent, one- and two-photon superposed states with the finite (quantized) number of peaks in the quantum regime. Our results may give a new insight into nonlinear quantum effects in microwave optics with artificial atoms.