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Dynamical quantum correlations of Ising models on an arbitrary lattice and their resilience to decoherence.

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Title: Dynamical quantum correlations of Ising models on an arbitrary lattice and their resilience to decoherence.
Authors: Foss-Feig, M1,2,3 michael.foss-feig@nist.gov, Hazzard, K R A4,5, Bollinger, J J5, Rey, A M4,5, Clark, C W1,2
Source: New Journal of Physics. Nov2013, Vol. 15 Issue 11, p113008-113039. 32p.
Subjects: Quantum correlations, Ising model, Lattice dynamics, Decoherence (Quantum mechanics), Polymer networks
Abstract: Ising models, and the physical systems described by them, play a central role in generating entangled states for use in quantum metrology and quantum information. In particular, ultracold atomic gases, trapped ion systems, and Rydberg atoms realize long-ranged Ising models, which even in the absence of a transverse field can give rise to highly non-classical dynamics and long-range quantum correlations. In the first part of this paper, we present a detailed theoretical framework for studying the dynamics of such systems driven (at time t = 0) into arbitrary unentangled non-equilibrium states, thus greatly extending and unifying the work of Foss-Feig et al (2013 Phys. Rev. A 87 042101). Specifically, we derive exact expressions for closed-time-path ordered correlation functions, and use these to study experimentally relevant observables, e.g. Bloch vector and spin-squeezing dynamics. In the second part, these correlation functions are then used to derive closed-form expressions for the dynamics of arbitrary spin-spin correlation functions in the presence of both T1 (spontaneous spin relaxation/excitation) and T2 (dephasing) type decoherence processes. Even though the decoherence is local, our solution reveals that the competition between Ising dynamics and T1 decoherence gives rise to an emergent non-local dephasing effect, thereby drastically amplifying the degradation of quantum correlations. In addition to identifying the mechanism of this deleterious effect, our solution points toward a scheme to eliminate it via measurement-based coherent feedback. [ABSTRACT FROM AUTHOR]
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Database: Engineering Source
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Abstract:Ising models, and the physical systems described by them, play a central role in generating entangled states for use in quantum metrology and quantum information. In particular, ultracold atomic gases, trapped ion systems, and Rydberg atoms realize long-ranged Ising models, which even in the absence of a transverse field can give rise to highly non-classical dynamics and long-range quantum correlations. In the first part of this paper, we present a detailed theoretical framework for studying the dynamics of such systems driven (at time t = 0) into arbitrary unentangled non-equilibrium states, thus greatly extending and unifying the work of Foss-Feig et al (2013 Phys. Rev. A 87 042101). Specifically, we derive exact expressions for closed-time-path ordered correlation functions, and use these to study experimentally relevant observables, e.g. Bloch vector and spin-squeezing dynamics. In the second part, these correlation functions are then used to derive closed-form expressions for the dynamics of arbitrary spin-spin correlation functions in the presence of both T1 (spontaneous spin relaxation/excitation) and T2 (dephasing) type decoherence processes. Even though the decoherence is local, our solution reveals that the competition between Ising dynamics and T1 decoherence gives rise to an emergent non-local dephasing effect, thereby drastically amplifying the degradation of quantum correlations. In addition to identifying the mechanism of this deleterious effect, our solution points toward a scheme to eliminate it via measurement-based coherent feedback. [ABSTRACT FROM AUTHOR]
ISSN:13672630
DOI:10.1088/1367-2630/15/11/113008