Date of Graduation

5-2021

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Physics (PhD)

Degree Level

Graduate

Department

Physics

Advisor/Mentor

Xiao, Min

Committee Member

Gea-Banacloche, Julio R.

Second Committee Member

Singh, Surendra P.

Third Committee Member

Vyas, Reeta

Fourth Committee Member

Arnold, Mark E.

Keywords

Magnomechanical phonon laser; Non-Hermitian photonics; Quantum noise

Abstract

In this dissertation, we have investigated quantum dynamics via three case studies. First, we studied a system of two coupled waveguides respectively carrying optical damping and optical gain in addition to squeezing elements in one or both waveguides. Such a system is expected to generate highly entangled light fields in the two waveguides. We, however, show that the degree of the created entanglement is significantly affected by the quantum noises associated with the amplification and dissipation. Because of the noise effect, one can only have nonzero entanglement for a limited time interval. Second, we generalized the first project by considering the gain saturation effect. The nonclassical properties of light are highly relevant to the gain saturation that influences the quantum noise. We explained the impact of gain saturation on a quantum light field dynamically evolving in the coupled system. In contrast to the ideal situation without gain saturation, one can achieve a steady state under the gain saturation. Moreover, gain saturation reduces the influence of amplification noise and thereby better preserves such quantum features as entanglement. We illustrate the effects of gain saturation by examining the time evolution of theWigner function, the entanglement of the light fields, and the cross-correlation function between the two output modes. Significant differences exist between unsaturated and saturated situations, especially for low photon numbers. Finally, we studied a magnomechanical phonon laser beyond the steady-state that includes a microwave cavity with a ferromagnetic sphere installed in it. The system is simultaneously driven by a microwave field and a constant magnetic field. Using the decomposition of the time evolution operator, we linearize the equations of motion and solve them numerically. Our results show there is an oscillatory population inversion between the optical supermodes. However, it is possible to obtain stimulated phonons with relatively high numbers provided the system is operating in the resonant condition and the power of the drive field is higher than its threshold.

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