arXiv:quant-ph/9908064 · Physical Review A

Decoherence-free subspaces for multiple-qubit errors. I. Characterization

Daniel A. Lidar, Dave Bacon, Julia Kempe, K. Birgitta Whaley

Published Jan 17, 2001• 89 citations

Abstract

Coherence in an open quantum system is degraded through its interaction with a bath. This decoherence can be avoided by restricting the dynamics of the system to special decoherence-free subspaces. These subspaces are usually constructed under the assumption of spatially symmetric system-bath coupling. Here we show that decoherence-free subspaces may appear without spatial symmetry. Instead, we consider a model of system-bath interactions in which to first order only multiple-qubit coupling to the bath is present, with single-qubit system-bath coupling absent. We derive necessary and sufficient conditions for the appearance of decoherence-free states in this model, and give a number of examples. In a sequel paper we show how to perform universal and fault tolerant quantum computation on the decoherence-free subspaces considered in this paper.

DOI: 10.1103/physreva.63.022306

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