Dissipative dynamics of a two-qubit system: Four-level lasing

TL;DR

This paper investigates the dissipative behavior of two flux qubits using Bloch-Redfield formalism, revealing flux-dependent relaxation rates and proposing mechanisms for four-level lasing in such systems.

Contribution

It introduces a detailed theoretical analysis of flux-dependent relaxation in two-qubit systems and proposes lasing mechanisms based on these dynamics.

Findings

Relaxation rates strongly depend on magnetic fluxes.

Flux control enables tuning of inter-level relaxation.

Proposed mechanisms for four-level lasing in flux qubits.

Abstract

The dissipative dynamics of a two-qubit system is studied theoretically. We make use of the Bloch-Redfield formalism which explicitly includes the parameter-dependent relaxation rates. We consider the case of two flux qubits, when the controlling parameters are the partial magnetic fluxes through the qubits' loops. The strong dependence of the inter-level relaxation rates on the controlling magnetic fluxes is demonstrated for the realistic system. This allows us to propose several mechanisms for lasing in this four-level system.