Single-atom maser with engineered circuit for population inversion

TL;DR

This paper proposes a superconducting circuit-based single-atom maser with engineered population inversion, demonstrating different operational regimes and overcoming photon blockade through auxiliary cavity coupling.

Contribution

It introduces a novel circuit design for a single-atom maser with engineered relaxation pathways and analyzes its operation in various coupling regimes.

Findings

Operates in both intermediate and strong coupling regimes

Exhibits thresholdless and threshold-dependent behaviors

Overcomes photon blockade with auxiliary resonator

Abstract

We present a blueprint for a maser with a single three-level transmon superconducting artificial atom. The system can be pumped coherently via a two-photon process, and to achieve high population inversion, the relaxation rate of the metastable state is increased via an auxiliary low-Q cavity coupled to a transition between the transmon excited states. We show numerically that such a maser can operate both in the intermediate coupling regime with super-Poissonian photon statistics and in the strong coupling regime, where the statistics is sub-Poissonian. For the former, the maser exhibits thresholdless behavior and for the latter, there is a well-defined pumping threshold. A useful side-effect of the auxiliary resonator is that it allows to overcome the photon blockade effect for the pump, which would otherwise prevent high photon population. Finally, we observe the bistability of the steady-state Wigner function and the self-quenching effect for some parameters.