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Entanglement and Decoherence in Optomechanical Systems Coupled through Photothermal Effects

Abdi, Mehdi | 2012

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 43396 (04)
  4. University: Sharif University of Technology
  5. Department: Physics
  6. Advisor(s): Bahrampour, Alireza
  7. Abstract:
  8. Optomechanical systems have attracted considerable attention in the last decade. Such a raising prominence is mainly due to its capability in providing new insight into the quantum behavior of macroscopic objects and exploring the interface between quantum and classical mechanics. Alongside this fundamental quest, cavity optomechanics has many other benefits, ranging from very precise measurements on forces and positions to quantum information processing. In this thesis, we investigate quantum properties of such systems. Particularly, we study cooling of the mechanical resonator toward its ground state and the entanglement between this mechanical resonator and the cavity field. Cooling the mechanical resonator is a necessary preliminary to preparing quantum states for the purpose of fundamental investigations (cat state) or measurement of weak forces (squeezed state). The entanglement between the optical field and the mechanical resonator is of fundamental interest while also having important potential applications. Therefore, it is necessary to investigate the technical limitations on the cooling process and the optomechanical entanglement. Laser phase noise could be very dangerous for both of them especially the entanglement. Thus, we first study effect of phase noise on the generation of the optomechanical entanglement and cooling process. In this thesis, we propose promising methods to considerably decrease destructive effects of this technical noise. Also, the inherently dissipative photothermal force, is an optical force, which usually participates in optomechanical coupling. We study effects of this force both on optomechanical cooling and entanglement. We show that surprisingly, even though the photothermal force is dissipative, it is may improve cooling of the mechanical resonator toward its ground state, and the optomechanical entanglement of the system. Such a enhancement in the optomechanical entanglement is not only in value, but also in its robustness against temperature. We extend our studies about the effects of the bolometric force to atom–optomechanical hybrid systems. The investigations reveals that the robustness of the atom–mirror entanglement in such systems significantly increases by photothermal coupling
  9. Keywords:
  10. Refrigeration ; Optomechanical Entanglement ; Photothermal Force ; Micromechanical Resonator ; Atomic Ansemble

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