Research On Ground State Cooling Of The Mechanical Resonator In Hybrid Cavity Optomechanical Systems

With the development of nano processing technology,major breakthroughs have been made in the preparation and research of cavity optomechanical systems.Cavity optomechanical system plays an important role in the high-precision measurement of biosensing,mechanical displacement,gravitational waves and mass.On the other hand,cavity optomechanical system is an ideal platform to verify the basic principles of quantum mechanics and study the properties of mesoscopic quantum dynamics.The ground state cooling of the mechanical resonator is a key issue in cavity optomechanics,and it is a prerequisite for observing its quantum behavior in the quantum region.Therefore,the ground state cooling of the mechanical resonator has become an important research topic.The currently known cooling theories and realized cooling schemes are mostly concentrated in the resolved sideband region.This requires more stringent experimental conditions.In addition,due to the influence of environmental thermal noise,the mechanical resonator cannot avoid the interference of environmental heating during the cooling process,so the cooling limit of the mechanical resonator has not been reduced to a very low level.Based on the above considerations,this article focuses on the unresolved sideband region and proposes two fast ground state cooling schemes.The ground-state cooling of the mechanical resonator of the hybrid double-cavity optomechanical system is studied.The atomic ensemble and auxiliary cavity are simultaneously coupled to the same optical cavity,forming a double quantum destructive interference channel.This causes the optical noise spectrum to show an electromagnetically induced transparency(EIT)-like linear shape,that is,the Stokes heating rate and the anti-Stokes cooling rate are asymmetric.By analyzing the optical mode Hamiltonian,the new normal mode frequency of the system is derived.By adjusting the peak and valley positions of the optical noise spectrum,the net cooling rate of the system is maximized,and the best parameters of ground state cooling are obtained.According to Fermi's golden rule,the analytical expression of the average number of phonons in steady state is given.Finally,the influence of the relevant system parameters on the cooling limit of the mechanical resonator is analyzed in detail.The results show that this scheme can achieve ground state cooling of the mechanical resonator in the unresolved region of the sideband.which provides a new idea for ground state cooling in multi-quantum systems.The intracavity-squeezed cooling in the parity time(PT)symmetrical double-cavity optomechanical system is studied.This scheme uses the energy localization effect of the PT symmetric cavity optomechanical system on the physical model,which greatly accelerates the cooling rate of the mechanical resonator.In addition,pump light is used to drive the optical parametric amplifier in the cavity,and a strong squeezed effect is formed in the cavity field.By analyzing its optical noise spectrum,the results show that the value of its trough is equal to zero,that is,the quantum reaction heating is completely suppressed.Therefore,this solution further reduces the cooling limit.In addition,the optimal cooling conditions and the optimal parameters of the pump light are given.Finally,by adjusting the system parameters,the ground state cooling of the mechanical resonator can be achieved when the sideband is in highly unresolved sideband region.This scheme is of great significance for studying the quantum manipulation of macroscopic mechanical resonator.