Scalable all-optical cold damping of levitated nanoparticles

Abstract

The field of levitodynamics has made significant progress towards controlling and studying the motion of a levitated nanoparticle. Motional control relies on either autonomous feedback via a cavity or measurement-based feedback via external forces. Recent demonstrations of measurementbased ground-state cooling of a single nanoparticle employ linear velocity feedback, also called cold damping, and require the use of electrostatic forces on charged particles via external electrodes.Here we introduce a novel all-optical cold damping scheme based on spatial modulation of the trap position that is scalable to multiple particles. The scheme relies on using programmable optical tweezers to provide full independent control over trap frequency and position of each tweezer. We show that the technique cools the center-of-mass motion of particles along one axis down to 17 mK at a pressure of 2 × 10 −6 mbar and demonstrate its scalability by simultaneously cooling the motion of two particles. Our work paves the way towards studying quantum interactions between particles, achieving 3D quantum control of particle motion without cavity-based cooling, electrodes or charged particles, and probing multipartite entanglement in levitated optomechanical systems.

Nanoscale feedback control of six degrees of freedom of a near-sphere

“…The nanoparticle is neutralized 6 , 27 , 28 and has an average radius of 176(3) nm. The translational motion along the optical lattice ( z direction) is cooled to an occupation number of n z = 0.69(18) via optical feedback cooling realized by controlling the optical gradients 6 , 29 , as shown in the power spectral density (PSD) obtained with photodetectors (Fig. 2 a).…”

Tuneable Gaussian entanglement in levitated nanoparticle arrays

“…Finally, to avoid the need for a large number of optical cavity modes to remove thermal noise from long nanoparticle arrays, coherent scattering can be complemented with measurement feedback 74 . Measurement-based feedback has recently been used to cool nanoparticle motion to the quantum ground state 17,18 and this approach can be scaled to multiple particles 75 . When combined with direct coupling between nanoparticles (mediated by the Coulomb force), it can be used to create steady-state entanglement as well 76 .…”

Cavity-mediated long-range interactions in levitated optomechanics

“…However, in addition to the challenge of ground-state cooling massive objects, such endeavours require either large-scale delocalization of a single object, or the entanglement of multiple objects. Levitodynamics, which deals with controlling the mechanical motion of massive oscillators in vacuum [2,4], has made remarkable headway towards multiple-particle systems, with demonstrations of cooling [5] and short-range coupling [6][7][8][9][10][11] between nanoparticles levitated in free space. Furthermore, recent experiments with single particles in optical tweezers have established exquisite control over rotational dynamics [12][13][14][15], and achieved quantum ground-state cooling of mechanical motion [16][17][18][19][20][21].…”

“…Here, we introduce such a capability to engineer strong programmable cavity-mediated interactions between multiple spatially separated particles in vacuum. The programmability arises from the use of acousto-optic deflec-tors (AODs) to generate tweezer arrays for trapping the particles [5,24], which offer a high degree of control over parameters such as optical frequencies of the tweezers, cavity detuning, as well as mechanical frequencies and position of the particles. Such parameter control is crucial for precisely tuning the interaction strength and for choosing which particles and mechanical modes couple.…”