Double Quantum Dot Floquet Gain Medium

TL;DR

This paper demonstrates that a strongly driven double quantum dot acts as a Floquet gain medium, exhibiting population inversion and cavity photon generation without a dc current, advancing quantum light sources and driven quantum system studies.

Contribution

It introduces the concept of a Floquet gain medium in a double quantum dot, showing population inversion and photon generation under strong periodic driving without a dc current.

Findings

Population inversion in Floquet quasi-energy levels.

Large intra-cavity photon number without cavity drive.

Operation without a dc current, driven by repeated excitation.

Abstract

Strongly driving a two-level quantum system with light leads to a ladder of Floquet states separated by the photon energy. Nanoscale quantum devices allow the interplay of confined electrons, phonons, and photons to be studied under strong driving conditions. Here we show that a single electron in a periodically driven DQD functions as a "Floquet gain medium," where population imbalances in the DQD Floquet quasi-energy levels lead to an intricate pattern of gain and loss features in the cavity response. We further measure a large intra-cavity photon number n_c in the absence of a cavity drive field, due to equilibration in the Floquet picture. Our device operates in the absence of a dc current -- one and the same electron is repeatedly driven to the excited state to generate population inversion. These results pave the way to future studies of non-classical light and thermalization of driven quantum systems.