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Coherent Effects in Dispersive Quantum Dynamics

Ye, S; (2012) Coherent Effects in Dispersive Quantum Dynamics. Doctoral thesis , UCL (University College London). Green open access

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This doctoral dissertation is concerned with the study of quantum dynamics where finite dimensional systems (typically two-level `qubits') interact with or through a set of bosonic modes, in various different configurations. Our main focus is on identifying and investigating signatures of quantum coherence emerging between the qubits in such dynamical situations. We first present a toy model where two qubits are encoded in the single-excitation subspace of the global system and study the average fidelity of a controlled-Z (CZ) quantum gate mediated by the bosonic modes. Next, we turn to analytically intractable spin-boson like models, by adopting the Multi-configurational Ehrenfest (MCE) method. We apply MCE to the study of the Choi fidelity of a CZ gate between two distant qubits, mediated by sets of bosonic modes (including sets which represent discretization of bath's continua) under different coupling Hamiltonians. The testing of the MCE method is then pushed further by a comparative analysis with full variational approaches and adiabatic path integral techniques in a case of super-Ohmic spin-boson model. Finally, we determine a general error bound applicable to most approximated treatments of unitary quantum evolutions, and suitable to compare MCE with other numerical techniques for the study of spin-boson dynamics.

Type: Thesis (Doctoral)
Title: Coherent Effects in Dispersive Quantum Dynamics
Open access status: An open access version is available from UCL Discovery
Language: English
UCL classification: UCL > School of BEAMS
UCL > School of BEAMS > Faculty of Maths and Physical Sciences
URI: http://discovery.ucl.ac.uk/id/eprint/1353701
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