6 GHz hyperfast rotation of an optically levitated nanoparticle in vacuum

Abstract

We report an experimental observation of a record-breaking ultra-high rotation frequency about 6 GHz in an optically levitated nanosphere system. We optically trap a nanosphere in the gravity direction with a high numerical aperture objective lens, which shows significant advantages in compensating the influences of the scattering force and the photophoretic force on the trap, especially at intermediate pressures (about 100 Pa). This allows us to trap a nanoparticle from atmospheric to low pressure (10 −3 Pa) without using feedback cooling. We measure a highest rotation frequency about 4.3 GHz of the trapped nanosphere without feedback cooling and a 6 GHz rotation with feedback cooling, which is the fastest mechanical rotation ever reported to date. Our work provides useful guides for efficiently observing hyperfast rotation in the optical levitation system, and may find various applications such as in ultrasensitive torque detection, probing vacuum friction, and testing unconventional decoherence theories.

Quantum rotations of nanoparticles

“…Current experiments align nanoscale rotors with millirad precision [3][4][5][6][7], spin them at GHz frequencies [5,6,8], and cool their rotations to sub-Kelvin temperatures [12][13][14]. Controlling and cooling microscale rotations requires novel strategies to handle their peculiar motion, as described by the non-linear Euler equations for the angular velocity in presence of non-harmonic torques.…”

“…The maximal rotation speed is determined by gas damping [3,4,[30][31][32] and ultimately by material stresses [33]. Experimentally demonstrated rotation rates reach GHz-frequencies [5,6,8,9], where centrifugal forces start deforming the particle.…”

“…Researchers in the field of levitated optomechanics [2] are perfecting their techniques: State-of-the-art experiments control nanoparticle rotations with ultra-high precision [3][4][5][6][7], spin them with unprecedented rotation frequencies [5,6,8], achieve record-breaking torque sensitivities [9], and cool nanoparticles into their center-of-mass ground state [10,11]. In a typical setup, a sub-micron dielectric particle is optically, electrically, or magnetically levitated in ultra-high vacuum and coherently interfaced with a laser field, serving to cool and manipulate the nanoparticle motion.…”