Cooling of a levitated nanoparticle to the motional quantum ground state

Owing to its excellent isolation from the thermal environment, an optically levitated silica nanoparticle in ultra-high vacuum has been proposed to observe quantum behavior of massive objects at room temperature, with applications ranging from sensing to testing fundamental physics. As a first step towards quantum state preparation of the nanoparticle motion, both cavity and feedback cooling methods have been used to attempt cooling to its motional ground state, albeit with many technical difficulties. We have recently developed a new experimental interface, which combines stable (and arbitrary) trapping potentials of optical tweezers with the cooling performance of optical cavities, and demonstrated operation at desired experimental conditions [1]. In order to overcome still existent technical problems we implemented a new cooling method – cavity cooling by coherent scattering – which we employ to demonstrate ground state cooling of the nanoparticle motion [2, 3]. In this talk I will present our latest experimental result on motional ground state cooling of a levitated nanoparticle and discuss next steps toward macroscopic quantum states.

[1] Delic, Grass et al., QST 5 (2), 025006
[2] Delic et al., Phys. Rev. Lett. 122, 123602
[3] Delic et al., Science 367, 892-895