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Title: Quantum Chaos and Correlations in Multipartite Systems
Keywords: Quantum correlations, chaos, quantum thermal machines, multipartite systems, circuit QED, Rabi model
Issue Date: 21-Aug-2014
Source: TEO YON SHIN (2014-08-21). Quantum Chaos and Correlations in Multipartite Systems. ScholarBank@NUS Repository.
Abstract: In this thesis, we examine the dynamics, quantum correlations and the emergence of quantum chaos in multipartite systems, with emphasis on systems composed of strongly interacting discrete and continuous variables subsystems. Starting from analyzing the entanglement dynamics in triqubit and three coupled oscillators systems, we comment on the role of environment on the sudden disappearances and rebirths of entanglement, and demonstrate how local single mode squeezing can spuriously lead to enhancement of multipartite entanglement. Next we show how finite, chaotic system may serve as an environment by considering a biqubit system weakly attached to two coupled anharmonic oscillators. Due to recent breakthough in engineering strong interaction in such discrete-continuous composite systems, it is important to understand the dynamics in chaotic regime where the rotating wave approximation (RWA) can no longer be applied. With the construction of the double Rabi model, we point out the importance of specifying the class of entanglement, in addressing the role of chaos in the steady state structure as well as dynamical generation of entanglement. We provide strong evidence that chaos in general suppresses entanglement that does not fully involve all degrees of freedom in the chaotic system, while enhancing global, multipartite entanglement. Three different aspects of the entanglement dynamics in chaotic regime are presented, namely the failure of entanglement transfer picture in chaos, evolution of noisy decoherence free state stabilized by chaos, and two competing effects of chaos in entanglement generation: chaos induced coherence and decoherence. Discord is regarded as a more fundamental quantum correlation measure than entanglement. While discord has been studied in the quantum phase transition of integrable systems, its behavior in the finite counterparts of these systems which usually exhibit chaotic behavior has not been reported. We show that, signatures of chaos can be identified with the fluctuations and production of quantum correlations in general, with discord showing more evident signatures. By exploiting the monogamy of quantum correlations which is a purely quantum mechanical effect, we demonstrate that these signatures can be enhanced dramatically. Finally we propose a new design of continuous quantum thermal machine based on Rabi model, which can be experimentally implemented in circuit QED. Depending on the coupling between the superconducting qubit and the LC resonator, the dynamics of the working components can be in quasiperiodic or highly chaotic regime. We show that in the former, the engine produces cooling effect on an ordinary qubit, while in the latter the engine functions as a heater instead.
Appears in Collections:Ph.D Theses (Open)

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