Dynamics of periodic anticrossings: Decoherence, pointer states and hysteresis curves

Abstract

We consider a strongly driven two-level (spin) system, with a periodic external field that induces a sequence of avoided level crossings. The spin system interacts with a bosonic reservoir which leads to decoherence. A Markovian dynamical equation is introduced without relying on the rotating wave approximation in the system-external field interaction. We show that the time evolution of the two-level system is directed towards an incoherent sum of periodic Floquet states regardless of the initial state and even the type of the coupling to the environment. Analyzing the time scale of approaching these time-dependent pointer states, information can be deduced concerning the nature and strength of the system-environment coupling. The inversion as a function of the external field is usually multi-valued, and the form of these hysteresis curves is qualitatively different for low and high temperatures. For moderate temperatures we found that the series of Landau-Zener-Stückelberg-type transitions still can be used for state preparation, regardless of the decoherence rate. Possible applications include quantum information processing and molecular nanomagnets.

arXiv comment10 pages, 9 slightly reduced quality figures, submitted to PRA; More details concerning applications to molacular nanomagnets are given

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Cited by in corpus (7)

• Landau-Zener-Stuckelberg interferometry
• Nonadiabatic Landau-Zener-Stückelberg-Majorana transitions, dynamics, and interference
• Thirty five classes of solutions of the quantum time-dependent two-state problem in terms of the general Heun functions
• Fifteen classes of solutions of the quantum two-state problem in terms of the confluent Heun function
• Nonlinear Landau-Zener Processes in a Periodic Driving Field
• Superparabolic Level Glancing Models for Two-State Quantum Systems
• Quadratic-nonlinear Landau-Zener transition for association of an atomic Bose-Einstein condensate with inter-particle elastic interactions included