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Optical Quantum Memories Based on Optomechanically Induced Transparency

Farman, Farnaz | 2015

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 47125 (04)
  4. University: Sharif University of Technology
  5. Department: Physics
  6. Advisor(s): Bahrampour, Alireza
  7. Abstract:
  8. Optomechanical systems have attracted much attention over the last decades, especially as a macroscopic lab for observing quantum mechanical effects . In this thesis , optomechanical quantum memories are studied . In p articularl , we study cooling of the mechanical resonator down to its ground state, which is the necessary condition to obtain a good quantum memory and also explore the limitations of cooling and storing protocols . Quantum state of light can be stored in the mechanical mode of the system by optomchanically induced transparency effect (OMIT) . This effect is formally equivalent to electromagnetically induced transparency effect (EIT) which is seen in an ensemble of lambda shape atoms . In OMIT method , a control laser tuned to the lower motional sideband of the cavity resonance , induces an optomechanical coupling between optical and mechanical degrees of freedom, which changes the response of the system to the input probe field . We study the optomechanical cavity as a quantum optical delay line and quantum memory . The mechanical mode of the system has to be cooled close to the quantum ground state . Thus , we consider the cooling process of oscillator in the presence of optical parametric amplifier (OPA) inside the cavity . One of the technical limitations to the cooling process is phase noise of the laser . We investigate the effect of OPA pump phase noise on the cooling of a micro-mirror (oscillator) . By introducing an optomechanical cavity containing two mechanical modes with different frequencies , we propose a protocol for simultaneous storing of two optical modes with different frequencies in the two mechanical modes of the system . Further investigation of this system , shows the intriguing effect of heat transfer between the two mechanical modes through an optical field in the cavity . By moving to the regime of strong optomechanical coupling, the storing protocol based on quantum state conversion between optical and mechanical mode is introduced. The storing fidelity of initial Gaussian state is obtained . Effect of environmental noises like thermal and quantum noises and also coupling laser phase noise on fidelity is investigated . We show that by increasing the coupling coefficient , the destructive effect of phase noise on fidelity increases
  9. Keywords:
  10. Refrigeration ; Fidelity ; Optical Quantum Memory ; Optomechanical Cavities ; Laser Phase Noise

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