Cavity cooling of an optically levitated submicron particle

Abstract

The coupling of a levitated submicron particle and an optical cavity field promises access to a unique parameter regime both for macroscopic quantum experiments and for high-precision force sensing. We report a demonstration of such controlled interactions by cavity cooling the center-of-mass motion of an optically trapped submicron particle. This paves the way for a light-matter interface that can enable room-temperature quantum experiments with mesoscopic mechanical systems.optical trapping | quantum optics | cavity optomechanics | nanoparticles | nanomechanics T he ability to trap and to manipulate individual atoms is at the heart of current implementations of quantum simulations (1, 2), quantum computing (3), and long-distance quantum communication (4,5). Controlling the motion of larger particles opens up avenues for quantum science, both for the study of fundamental quantum phenomena in the context of matter wave interference (6), and for unique sensing and transduction applications in the context of quantum optomechanics (7,8). Specifically, it has been suggested that cavity cooling of a single submicron particle in high vacuum allows for the generation of quantum states of motion in a room-temperature environment (9-11), as well as for unprecedented force sensitivity (12, 13). Here, we take steps into this regime. We demonstrate cavity cooling of an optically levitated submicron particle consisting of ∼10 9 atoms (estimated diameter of 340 nm). The particle is trapped at modest vacuum levels of a few millibars in the standingwave field of an optical cavity and is cooled through coherent scattering into the modes of the same cavity (14, 15). We estimate that our cooling rates are sufficient for ground-state cooling, provided that optical trapping at a vacuum level of 10 −7 mbar can be realized in the future, e.g., by using additional active-feedback schemes to stabilize the optical trap in three dimensions (16)(17)(18)(19).Cooling and coherent control of single atoms inside an optical cavity are well-established techniques within atomic quantum optics (20)(21)(22)(23)(24). The main idea of cavity cooling relies on the fact that the presence of an optical cavity can resonantly enhance scattering processes of laser light that deplete the kinetic energy of the atom, specifically those processes where a photon that is scattered from the atom is Doppler shifted to a higher frequency. It was realized early on that such cavity-enhanced scattering processes can be used to achieve laser cooling even of objects without exploitable internal level structure such as molecules and submicron particles (14,15,25,26). For nanoscale objects, cavity cooling has been demonstrated in a series of recent experiments with nanobeams (27-29) and membranes of nanometerscale thickness (e.g., refs. 30 and 31). To guarantee long interaction times with the cavity field, these objects were mechanically clamped, which however introduces additional dissipation and heating through the mechanical support structure. As a consequence, quantum...

Nonlinear Dynamics and Strong Cavity Cooling of Levitated Nanoparticles

“…While there has been success cooling nanoparticles with active feedback [23,24], passive cavity cooling has been hindered by particle loss processes which prevented optical trapping below a few mBar [22,26,27]. This "bottleneck" was overcome in [16] via the use of a hybrid electro-optical trap, and the subsequent improvements presented in this paper allow cooling to temperatures three orders of magnitude lower than previously reported [16,25,26].…”

“…Finally we identify a previously unobserved shift of the Paul trap secular frequencies due to the optical cavity, which we show gives valuable information on the system, such as the nanoparticle charge and mean number of photons in the cavity. The optomechanical cooling of levitated nanoparticles to the quantum regime has been the subject of several recent theoretical [18][19][20][21][22] and experimental [16,[23][24][25][26] studies, due to their isolation from environmental decoherence. While there has been success cooling nanoparticles with active feedback [23,24], passive cavity cooling has been hindered by particle loss processes which prevented optical trapping below a few mBar [22,26,27].…”

“…The optomechanical cooling of levitated nanoparticles to the quantum regime has been the subject of several recent theoretical [18][19][20][21][22] and experimental [16,[23][24][25][26] studies, due to their isolation from environmental decoherence. While there has been success cooling nanoparticles with active feedback [23,24], passive cavity cooling has been hindered by particle loss processes which prevented optical trapping below a few mBar [22,26,27]. This "bottleneck" was overcome in [16] via the use of a hybrid electro-optical trap, and the subsequent improvements presented in this paper allow cooling to temperatures three orders of magnitude lower than previously reported [16,25,26].…”

Optimal quantum parameter estimation in a pulsed quantum optomechanical system

“…Optomechanical systems have been implemented in many physical systems, such as suspended mirrors in the FabryPérot resonators [53], toroidal whispering gallery mode resonators [54], trapped levitating nanoparticles [55], ultracold atomic clouds in cavities [56]. Here we focus on a membrane-in-the-middle cavity optomechanical setup [57], which has been used for quantum nondemolition measurement of the phonon number state [58], cooling of mechanical resonator [59] or investigation of Landau-Zener-Stückelberg dynamics [60].…”

A Realization of a Quasi-Random Walk for Atoms in Time-Dependent Optical Potentials

“…In such a system, the time delay between the action of the field onto the atomic system's motion via the induced optical potential and the back-action of the particle's position change onto the cavity field leads to effects such as cooling [6][7][8] or self-oscillations (for a recent review see [9]). Addressing of the particle's motion works best for quantum emitters with sharp transitions such as ions or atoms but manipulation via the effective static polarizability is also possible in the case of molecules in standing wave [10] or ring cavities [11], or macroscopic particles such as levitated dielectric micron-sized spheres [12][13][14]. Typically, the driving is done either by direct pumping into the cavity mode via one of the side mirrors (longitudinal pumping), or indirectly via light scattering off the atom into the field mode (transverse pumping).…”