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Decoherence-Free Subspaces for Multiple-Qubit Errors: (I) Characterization

Daniel A. Lidar·Dave Bacon·Julia Kempe·K. B. Whaley
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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.

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Daniel A. Lidar, Dave Bacon, Julia Kempe, K. B. Whaley. 2000-07-05. Decoherence-Free Subspaces for Multiple-Qubit Errors: (I) Characterization. https://doi.org/10.1103/physreva.63.022306

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