Quantum Statistical Properties In Strong-Coupling Optomechanical Systems

Optomechanics is an interdisciplinary subject of mechanics and optics,and has important applications in many areas.Optomechanical systems serve not only to detect gravitational waves from distance universe,but also to perform ultra-precise measurements of tiny forces,displacements,and accelerations.With the development of optomechanics and fabrication techniques,it is now possible to realize optomechanical quantum effects at microscopic or macroscopic scales and even quantum-state control.In most currently-available optomechanical systems,the single photon-phonon coupling is extremely weak,and the corresponding quantum effects are essentially negligible.To enhance the actual quantum effects,one can use a laser pump to establish a quasi-stable optical state to increase the effective optomechanical coupling strength,and the quantum responses can be further enhanced by post-selection measurement.Alternatively,one can directly use optomechanical systems with sufficiently strong single-photon coupling strength.Indeed,a small number of optomechanical systems have approached or even reached the regime of strong single-photon coupling.In this thesis,we will study quantum effects in strong-coupling optomechanical systems based on the above two mechanisms of coupling enhancement.In Chapter 3,we study photon-phonon pairs with both continuous-variable and discrete-variable entanglements in a laser-pumped optomechanical resonator-waveguide system.The analytical wave function of the photon-phonon pair is deduced by the“backward Heisenberg picture approach,and the quantum properties such as the entanglement in the photon-phonon pair are analyzed.Based on the above results,mechanisms for independently controlling the discrete-variable and continuous-variable entanglements are proposed.In Chapter 4,we study nonlinear quantum effects in single-photon strong coupling optomechanical systems.By numerically solving the density-operator master equation of the system,we calculate the particle number distribution and second-order correlation function of the optical field.Based on the results,the impacts of thermal noise on nonlinear quantum effects such as sub-Poissonian distribution and anti-bunching effect of photons are analyzed.We find that quantum effect in the two-time second-order optical correlation function manifests strong robustness against mechanical thermal noises.Our work would benefit quantum optics and quantum information in two aspects.On the one hand,by realizing more valuable optomechanical quantum effects,it would enrich the physics of quantum optics;on the other hand,by implementing novel quantum-state generation and control,it would offer high-quality quantum-bit resources and experimental schemes for quantum information processing.