Ground-state cooling of a mechanical oscillator in a hybrid optomechanical system including an atomic ensemble

Wei Zeng,Wenjie Nie,Aixi Chen,Ling Li

doi:10.1038/s41598-017-16956-4

Abstract

We investigate dynamical properties and the ground-state cooling of a mechanical oscillator in an optomechanical system coupling with an atomic ensemble. In this hybrid optomechanical system, an atomic ensemble which consists of two-level atoms couples with the cavity field. Here we consider the case where the atomic ensemble is in higher excitation. Studies show that the atom-field coupling strength can obviously influence the cooling process, and we can achieve the ground-state cooling of the mechanical oscillator by choosing the appropriate physical parameters of the system. Our cooling mechanism has potential applications in quantum information processing and procession measurement.

Highlights

With the development of quantum optomechanical techniques, more and more attentions focus on the studies of the cavity optomechanics and its application[1,2,3,4,5]
We derive the expressions of the effective frequency ωeff and the effective damping rate γeff for the movable mirror, which depend on the averaged atom-field coupling strength and the atomical excitation number
We consider three kinds of couplings: the coupling between the cavity field and the mechanical oscillator, the coupling of the cavity field with the driving laser field, and the coupling of the cavity interacting with the atomic ensembles

Summary

Model and Theory

We consider a hybrid setup including a typical optomechanical system and an atomic ensemble which consists of lots of atom with two-level energy (see Fig. 1). Where the first term is the energy of the intracavity field; a†(a) is the creation (annihilation) operator of the cavity mode satisfying the commutation relation [a, a†] = 1. The commutation and the excited state of the i th two-level atom relations for the pseudospin-1/2 operators σ+i = |e〉(i)(i)〈g| and σ−(i) = |g〉(i)(i)〈e| are [σ+(i), σ−(i)] = σz(i) and [σz(i), σ±(i)] = ±2σ±(i), respectively. The third and fourth terms are the kinetic energy and potential energy of the movable mirror with position operator q and momentum operator p satisfying the commutation relation[q, p] = i. The first term in the second line gives the interaction between the atomic ensemble and the cavity mode, where g represents the averaged atom-field coupling strength[28,48]. The last term in the total Hamiltonian describes the interaction between the cavity field and the coupling field with the amplitude εc =.

Dynamical Properties of System

Results and Discussions

Conclusion

Additional Information