Generalized Dynamical Decoupling from the Quantum Zeno Effect
Paolo Facchi, Daniel A. Lidar, Saverio Pascazio · arXiv (Cornell University) · 2003
We unify the quantum Zeno effect (QZE) and "bang-bang" (BB) decoupling, recently introduced as a 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 BB to arbitrary fast and strong pulse sequences, requiring no symmetry. We further point out that the inverse QZE implies that BB can in some cases accelerate, rather than inhibit, decoherence.