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arXiv · 1302.0037

Unavoidable decoherence in the quantum control of an unknown state

D. Kielpinski·R. A. Briggs·H. M. Wiseman
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Abstract

A common objective for quantum control is to force a quantum system, initially in an unknown state, into a particular target subspace. We show that if the subspace is required to be a decoherence-free subspace of dimension greater than 1, then such control must be decoherent. That is, it will take almost any pure state to a mixed state. We make no assumptions about the control mechanism, but our result implies that for this purpose coherent control offers no advantage, in principle, over the obvious measurement-based feedback protocol.

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D. Kielpinski, R. A. Briggs, H. M. Wiseman. 2013-01-31. Unavoidable decoherence in the quantum control of an unknown state. https://doi.org/10.2478/qmetro-2013-0001

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