Microwave Quantum Optics with an Artificial Atom

TL;DR

This paper reviews advances in microwave quantum optics using artificial atoms, demonstrating strong nonlinearity and quantum devices like routers and filters crucial for on-chip quantum networks.

Contribution

It reports the experimental realization of quantum devices at the single-photon level in microwave regime using artificial atoms without cavities.

Findings

Observation of strong nonlinearity in artificial atoms

Demonstration of Mollow triplet under strong driving

Implementation of single-photon router and photon-number filter

Abstract

We address the recent advances on microwave quantum optics with artificial atoms. This field relies on the fact that the coupling between a superconducting artificial atom and propagating microwave photons in a 1D open transmission line can be made strong enough to observe quantum coherent effects, without using any cavity to confine the microwave photons. We investigate the scattering properties in such a system with resonant coherent microwaves. We observe the strong nonlinearity of the artificial atom and under strong driving we observe the Mollow triplet. By applying two resonant tones, we also observe the Autler-Townes splitting. By exploiting these effects, we demonstrate two quantum devices at the single-photon level in the microwave regime: the single-photon router and the photon-number filter. These devices provide essential steps towards the realization of an on-chip quantum network.