Gain-assisted superluminal microwave pulse propagation via four-wave mixing in superconducting phase quantum circuits

TL;DR

This paper demonstrates superluminal microwave pulse propagation and amplification without inversion in a superconducting quantum circuit, achieved through four-wave mixing and external flux control, with potential for tunable quantum signal processing.

Contribution

It introduces a method to achieve gain-assisted superluminal microwave propagation in superconducting circuits via four-wave mixing without requiring population inversion.

Findings

Superluminal microwave propagation achieved with increased pump tones.

Microwave amplification without population inversion demonstrated.

Group velocity controlled by external magnetic fluxes.

Abstract

We study the propagation and amplification of a microwave field in a four-level cascade quantum system which is realized in a superconducting phase quantum circuit. It is shown that by increasing the microwave pump tones feeding the system, the normal dispersion switches to the anomalous and the gain-assisted superluminal microwave propagation is obtained in this system. Moreover, it is demonstrated that the stimulated microwave field is generated via four-wave mixing without any inversion population in the energy levels of the system (amplification without inversion) and the group velocity of the generated pulse can be controlled by the external oscillating magnetic fluxes. We also show that in some special set of parameters, the absorption-free superluminal generated microwave propagation is obtained in superconducting phase quantum circuit system.