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Collective States and Symmetric Local Decoherence in Large Ensembles of Qubits
Bradley A. Chase and JM Geremia
Department of Physics and Astronomy, The University of New Mexico, Albuquerque NM 87131 USA
Abstract. The symmetric collective states of an atomic spin ensemble (i.e., many-body states that are invariant under particle exchange) are not preserved by decoherence that acts identically but individually on members of the ensemble. We develop a class of collective states in an ensemble of N spin-1/2 particles that is invariant under symmetric local decoherence and find that the dimension of the Hilbert space spanned by these collective states scales only as N2. We then investigate the open system dynamics of experimentally relevant non-classical collective atomic states, including Schroedinger cat and spin squeezed states, subject to various symmetric but local decoherence models.
Background on the Paper
Originally, we had authored two papers on the subject of symmetric decoherence in ensembles of spin-1/2 particles. One of these papers was a short version, which focused on simulations that compared and contrasted the dynamics generated by collective versus symmetric decoherence processes. The second paper was much longer and contained the detailed derivation and induction proof of the equations in the short paper. During the referee process of the two papers, it was suggested that the two works be combined into one manuscript. We have retained the original short paper here and on the arXiv because it provides an accessible overview of the research results.
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- [Simulation Code and Data Files] (tar.gz file with Matlab source)