Environment-Governed Dynamics in Driven Quantum Systems

Abstract

We show that the dynamics of a driven quantum system weakly coupled to the environment can exhibit two distinct regimes. While the relaxation basis is usually determined by the system þ drive Hamiltonian (system-governed dynamics), we find that under certain conditions it is determined by specific features of the environment, such as, the form of the coupling operator (environment-governed dynamics). We provide an effective coupling parameter describing the transition between the two regimes and discuss how to observe the transition in a superconducting charge pump. Introduction.-Understanding how quantum systems interact with the environment [1] is of paramount importance in quantum information science. While unveiling how the classical world emerges from the quantum one [2], it can also lead to a better protection against decoherence effects on the way towards the realization of a quantum computer [3].A standard approach to the dynamics of open quantum systems boils the problem down to the measurement of decoherence rates, distinguishing between coherence loss, or dephasing, and relaxation. While this approach has successfully described a variety of quantum systems, it only offers a limited insight into the dynamics of decoherence. A promising line of work developed in the last decade exploits the possibility of coupling the system to an engineered reservoir [4][5][6][7][8][9][10][11][12].As new and more accurate ways are found of harnessing the dynamic evolution of quantum systems, it becomes increasingly important to understand how the interaction with the environment is affected by a time-dependent modulation of the system parameters. Indeed, the study of dissipation in driven quantum systems is a longestablished topic [13] that keeps finding new applications to quantum pumping [14][15][16], quantum computation [17,18], and possibly even biological systems [19,20].In this Letter, we consider a periodically driven quantum system in the presence of a weakly coupled environment. We show that under certain conditions decoherence takes place in a preferred basis determined by specific features of the environment, such as, the type of noise, rather than of the system. We label this unusual regime as environmentgoverned dynamics (EGD), as opposed to the more familiar system-governed dynamics (SGD). We introduce an effective coupling parameter that presides over the transition between SGD and EGD. This parameter can be tuned by changing the properties of the drive. Our analysis is general and applies to optical and solid-state systems alike.

Dynamic transition in Landau-Zener-Stückelberg interferometry of dissipative systems: The case of the flux qubit

“…44,[67][68][69][70] More precisely, this approximation can be justified when ε α −ε β L α β αβ , which is fulfilled for very weak coupling with the environment and away from resonances, see Ref. 67,70. From Fig.12(c) and (d) it is clear that this condition will be easily satisfied in the offresonant case considered here, where the Floquet gap |ε α − ε β | is large.…”

“…In the case of a system with a time periodic drive, it is usually assumed that for large times the density matrix becomes approximately diagonal in the Floquet basis. 44,[67][68][69][70] More precisely, this approximation can be justified when ε α −ε β L α β αβ , which is fulfilled for very weak coupling with the environment and away from resonances, see Ref. 67,70.…”

Observation of the Bloch-Siegert shift in a driven quantum-to-classical transition

“…The impedance Z(ω p ) was calculated from the probe induced transition rates between the quasienergy states of the driven cavity-transmon system by employing the Kramers-Kronig relation [17,33,[37][38][39][40][41][42][43][44]. We see that the RWA gives the overall qualitative behaviour relatively well but lacks the nonmonotonic behaviour of the simulated resonance frequency toward the high-power end of the spectrum.…”

Lamb-Shift Enhancement and Detection in Strongly Driven Superconducting Circuits

“…This drive cannot be treated as a perturbation and the interaction between the driven system and its environment is best described in terms of "dressed states" that recently have attracted much attention in superconducting circuits [20][21][22][23][24]. Under certain resonant conditions, the system-environment coupling is substantially enhanced by the presence of the drive, yielding a dynamic steady state, which is largely determined by environmental features itself [25][26][27]. Within the same regime, the environment also induces a renormalization of the dressed-state energies (quasienergies).…”