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3D Trapping, Cooling of a Nanoparticle and Optimal Control of a Heat Engine in a Quantum Optomechanical System

Bathaee, Marziehsadat | 2016

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 49090 (02)
  4. University: Sharif University of Technology
  5. Department: Physics
  6. Advisor(s): Bahrampour, Alireza
  7. Abstract:
  8. In this dissertation, we propose and analytically investigate a scheme for effective three-dimensional cooling of a nanoparticle optically trapped in a Fabry-Perot cavity using multiple cavity modes. By employing active feedback cooling using amplitude modulation of cavity modes, our approach allows to access the UHV regime without the need for any additional means like an external tweezer or a radio-frequency trapping approach. For a set of feasible experimental parameters, we demonstrate that the cooling rates achievable are sufficient to overcompensate recoil heating. Therefore the approach is suited to trap a particle for indefinite times at UHV pressures, where air damping cannot provide sufficient cooling. The scheme is compatible with axial ground-state cooling. We thus present a feasible path from state-of-the-art cavity-cooling experiments at high pressure to achieving the quantum regime for optomechanics with single, optically trapped nanoparticles.Then, we introduce an optomechanical quantum Otto heat engine which consists of a levitated nanoparticle in an optical cavity. The particle is assumed to be trapped by optical tweezers in the cavity whose pressure is a few millibar. We analyze the optomechanical cold bath of the system based on the entropy pumping approach. The system dynamics of the adiabatic stroke is studied. The quantum friction work and the optimal control to obtain the frictionless adiabatic stroke are derived. Finally, dynamics of an optomechanical heat engine in the strong coupling regime, where the system is characterized by two normal modes, are analyzed. While the system experiences quantum friction effects, the maximum extractable work of both optomechanical normal modes in minimum time is derived. We show the total work done by the system in the power adiabatic stroke is optimized by a bang-bang control.The time duration of the power adiabatic stroke is of the order of the inverse of the effective optomechanical-coupling coefficient. The optimal phase space trajectory of
    the Otto cycle for both optomechanical normal modes is also obtained
  9. Keywords:
  10. Optical Trapping ; Optimal Control ; Quantum Interference ; Refrigeration ; Optomechanical Cooling ; Quantum Heat Engine

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