Floquet states in dissipative open quantum systems

TL;DR

This paper explores how dissipation and decoherence affect the formation and stability of Floquet states in open quantum systems under periodic driving, revealing conditions for their observation despite environmental interactions.

Contribution

It provides a comprehensive theoretical analysis of Floquet states in dissipative open quantum systems, highlighting the roles of decoherence and driving strength in their formation.

Findings

Decoherence significantly disrupts Floquet states during resonant driving.

Rabi splitting can be observed with decoherence times as short as one-third of the Rabi cycle.

Floquet states can form under strong driving even with significant dissipation.

Abstract

We theoretically investigate basic properties of nonequilibrium steady states of periodically-driven open quantum systems based on the full solution of the Maxwell-Bloch equation. In a resonantly driving condition, we find that the transverse relaxation, also known as decoherence, significantly destructs the formation of Floquet states while the longitudinal relaxation does not directly affect it. Furthermore, by evaluating the quasienergy spectrum of the nonequilibrium steady states, we demonstrate that the Rabi splitting can be observed as long as the decoherence time is as short as one third of the Rabi-cycle. Moreover, we find that Floquet states can be formed even under significant dissipation when the decoherence time is substantially shorter than the cycle of driving, once the driving field strength becomes strong enough. In an off-resonant condition, we demonstrate that the Floquet states can be realized even in weak field regimes because the system is not excited and the decoherence mechanism is not activated. Once the field strength becomes strong enough, the system can be excited by nonlinear processes and the decoherence process becomes active. As a result, the Floquet states are significantly disturbed by the environment even in the off-resonant condition. Thus, we show here that the suppression of heating is a key condition for the realization of Floquet states in both on and off-resonant conditions not only because it prevents material damage but also because it contributes to preserving coherence.