Unavoidable decoherence in the quantum control of an unknown state
Quantum Physics
2013-10-28 v1
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.
Cite
@article{arxiv.1302.0037,
title = {Unavoidable decoherence in the quantum control of an unknown state},
author = {D. Kielpinski and R. A. Briggs and H. M. Wiseman},
journal= {arXiv preprint arXiv:1302.0037},
year = {2013}
}
Comments
3 pages. To be published in Quantum Measurements & Quantum Metrology http://versita.com/qm/