Overcoming photon blockade in circuit QED single-atom maser with engineered metastability and strong coupling

TL;DR

This paper demonstrates overcoming photon blockade in a circuit QED single-atom maser by engineering metastability and strong coupling, enabling high photon numbers and lasing features in a transmon-based system.

Contribution

The work introduces a method to surpass photon blockade in a single-atom maser using engineered dissipation and energy level modifications in a circuit QED setup.

Findings

Achieved pumping of over a dozen photons into the system.

Observed laser-like features such as linewidth narrowing and signal amplification.

Reported phenomena like self-quenching and multiple lasing thresholds.

Abstract

Reaching high cavity population with a coherent pump in the strong-coupling regime of a single-atom laser is impossible due to the photon blockade effect. In this work, we experimentally demonstrate that in a single-atom maser based on a transmon strongly coupled to two resonators it is possible to pump over a dozen of photons into the system. The first high-quality resonator plays a role of usual lasing cavity, and the second one presents a controlled dissipation channel, bolstering population inversion, and modifies the energy level structure to lift the blockade. As a confirmation of lasing action, we observe conventional laser features such as the narrowing of emission linewidth and external signal amplification. Additionally, we report unique single-atom features: self-quenching and several lasing thresholds.