Unification of dynamical decoupling and the quantum Zeno effect

P. Facchi, D. A. Lidar, and S. Pascazio
Phys. Rev. A 69, 032314 – Published 22 March 2004

Abstract

We unify the quantum Zeno effect (QZE) and the “bang-bang” (BB) decoupling method for suppressing decoherence in open quantum systems: in both cases strong coupling to an external system or apparatus induces a dynamical superselection rule that partitions the open system’s Hilbert space into quantum Zeno subspaces. Our unification makes use of von Neumann’ s ergodic theorem and avoids making any of the symmetry assumptions usually made in discussions of BB. Thus we are able to generalize the BB to arbitrary fast and strong pulse sequences, requiring no symmetry, and to show the existence of two alternatives to a pulsed BB: continuous decoupling and pulsed measurements. Our unified treatment enables us to derive limits on the efficacy of the BB method: we explicitly show that the inverse QZE implies that the BB can in some cases accelerate, rather than inhibit, decoherence.

  • Received 20 March 2003

DOI:https://doi.org/10.1103/PhysRevA.69.032314

©2004 American Physical Society

Authors & Affiliations

P. Facchi1, D. A. Lidar2, and S. Pascazio1

  • 1Dipartimento di Fisica, Università di Bari I-70126 Bari, Italy, and Istituto Nazionale di Fisica Nucleare, Sezione di Bari, I-70126 Bari, Italy
  • 2Chemical Physics Theory Group, Chemistry Department, University of Toronto, 80 St. George Street, Toronto, Ontario, Canada M5S 3H6

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Vol. 69, Iss. 3 — March 2004

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