Cavity Optomechanics with Cold Atoms

Abstract

The mechanical influence on objects due to their interaction with light has been a central topic in atomic physics for decades. Thus, not surprisingly, one finds that many concepts developed to describe cavity optomechanical systems with solid-state mechanical oscillators have also been developed in a parallel stream of scientific literature pertaining to cold atomic physics. In this chapter, I describe several of these ideas from atomic physics, including optical methods for detecting quantum states of single cold atoms and atomic ensembles, motional effects within single-atom cavity quantum electrodynamics, and collective optical effects such as superradiant Rayleigh scattering and cavity cooling of atomic ensembles. Against this background, I present several experimental realizations of cavity optomechanics in which an atomic ensemble serves as the mechanical element. These are divided between systems driven either by sending light onto the cavity input mirrors ("cavity pumped"), or by sending light onto the atomic ensemble ("side pumped"). The cavity-pumped systems clearly exhibit the key phenomena of cavity optomechanical systems, including cavity-aided position sensing, coherent back action effects such as the optical spring and cavity cooling, and optomechanical bistability; several of these effects have been detected not only for linear but also for quadratic optomechanical coupling. The extreme isolation of the atomic ensemble from mechanical disturbances, and its strong polarizability near the atomic resonance frequency, allow these optomechanical systems to be highly sensitive to quantum radiation pressure fluctuations. I describe several ways in which these fluctuations are observed experimentally. I conclude by considering the side-pumped cavity experiments in terms of cavity optomechanics, complementing recent treatments of these systems in terms of condensed-matter physics concepts such as quantum phase transitions and supersolidity.

Fermionic Superradiance in a Transversely Pumped Optical Cavity

“…The latter also established equivalence to the superradiance transition in an effective Dicke model [12][13][14][15][16][17]. These advances open the door to non-equilibrium and strongly correlated matter-light phenomena, including drivendissipative phase transitions [18,19], Mott insulator transitions in self-organized lattices [20,21] and cavity optomechanics [22]. They also provide a platform on which to explore frustrated spin models and glassy behavior in multimode cavities [23][24][25][26][27].…”

Cavity optomechanics with a trapped, interacting Bose-Einstein condensate

“…With nanomechanical oscillators, it still remains a challenge in the optical domain to reach simultaneously the quantum mechanical ground state and the quantum coherent regime, where the coupling exceeds both the optical and mechanical decoherence rates [2]. In contrast, these goals are relatively easily achieved with ultracold atoms [3,4,5]. Most remarkably, radiation pressure coupling can be simulated with a Bose-Einstein condensate (BEC) dispersively coupled to the field of a high-finesse optical cavity, that can be either a ring cavity [6,7,8,9] or a linear microcavity [10,11].…”

Mechanical Resonators for Quantum Optomechanics Experiments at Room Temperature

“…One of the most successful implementation of mechanical oscillators for such (quantum) optomechanics experiments are devices made of high-stress silicon nitride (Si 3 N 4 ), which have been utilized in quantum-limited accelerometers [14], coupling of their motion to ultracold atoms [15,16], optomechanics in 3D microwave cavities [17], microwave-to-optical wavelength conversion [18], and quadratic coupling in cavity optomechanics [19].…”