Two-level systems driven by large-amplitude fields

S. Ashhab, J. R. Johansson, A. M. Zagoskin, and Franco Nori
Phys. Rev. A 75, 063414 – Published 19 June 2007

Abstract

We analyze the dynamics of a two-level system subject to driving by large-amplitude external fields, focusing on the resonance properties in the case of driving around the region of avoided level crossing. In particular, we consider three main questions that characterize resonance dynamics: (1) the resonance condition, (2) the frequency of the resulting oscillations on resonance, and (3) the width of the resonance. We identify the regions of validity of different approximations. In a large region of the parameter space, we use a geometric picture in order to obtain both a simple understanding of the dynamics and quantitative results. The geometric approach is obtained by dividing the evolution into discrete time steps, with each time step described by either a phase shift on the basis states or a coherent mixing process corresponding to a Landau-Zener crossing. We compare the results of the geometric picture with those of a rotating wave approximation. We also comment briefly on the prospects of employing strong driving as a useful tool to manipulate two-level systems.

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  • Received 12 February 2007

DOI:https://doi.org/10.1103/PhysRevA.75.063414

©2007 American Physical Society

Authors & Affiliations

S. Ashhab1, J. R. Johansson1, A. M. Zagoskin1,2, and Franco Nori1,3

  • 1Frontier Research System, The Institute of Physical and Chemical Research (RIKEN), Wako-shi, Saitama 351-0198, Japan
  • 2Department of Physics and Astronomy, The University of British Columbia, Vancouver, BC, Canada V6T 1Z1
  • 3Physics Department and Michigan Center for Theoretical Physics, The University of Michigan, Ann Arbor, Michigan 48109-1040, USA

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Issue

Vol. 75, Iss. 6 — June 2007

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