Two-dimensional quantum motion of a levitated nanosphere
Authors: Ranfagni A.; Borkje K.; Marino F.; Marin F.
Autors Affiliation: European Laboratory for Non-Linear Spectroscopy (LENS), via Carrara 1, I-50019 Sesto Fiorentino (FI), Italy and INFN, Sezione di Firenze, via Sansone 1, I-50019 Sesto Fiorentino (FI), Italy.
Department of Science and Industry Systems, University of South-Eastern Norway, PO Box 235, NO-3603 Kongsberg, Norway.
CNR-INO, largo Enrico Fermi 6, I-50125 Firenze, Italy and INFN, Sezione di Firenze, via Sansone 1, I-50019 Sesto Fiorentino (FI), Italy.
Dipartimento di Fisica e Astronomia, Università di Firenze, via Sansone 1, I-50019 Sesto Fiorentino (FI), Italy.
Abstract: We report on the two-dimensional (2D) dynamics of a levitated nanoparticle in an optical cavity. The motion of the nanosphere is strongly coupled to the cavity field by coherent scattering and heavily cooled in the plane orthogonal to the tweezer axis. Due to the characteristics of the 2D motion and the strong optomechanical coupling, the motional sideband asymmetry that reveals the quantum nature of the dynamics is not limited to mere scale factors between Stokes and anti-Stokes peaks, as customary in quantum optomechanics, but assumes a peculiar spectral dependence. We introduce and discuss an effective thermal occupancy that quantifies how close the system is to a minimum uncertainty state and allows us to consistently characterize the particle motion. By rotating the polarization angle of the tweezer beam we tune the system from a 1D cooling regime, where we achieve a best thermal occupancy of 0.51±0.05, to a regime in which the fully 2D dynamics of the particle exhibit strong nonclassical properties. We achieve a strong 2D confinement with thermal occupancy of 3.4±0.4 along the warmest direction and around one in the orthogonal one. These results represent a major improvement over previous experiments considering both the 1D and the 2D motion and pave the way toward the preparation of tripartite optomechanical entangled states and novel applications to directional force and displacement quantum sensing.
Journal/Review: PHYSICAL REVIEW RESEARCH
Volume: 4 Pages from: 033051-1 to: 033051-10
More Information: We thank A. Boschetti for the measurement of the nanopar- ticles diameter. Research was performed within the Project QuaSeRT (also Research Council of Norway Project Num- ber 285616) , funded by the QuantERA ERA -NET Cofund in Quantum Technologies implemented within the European Union?s Horizon 2020 Programme.KeyWords: Cavity-optomechanics, levitated nanoparticlesDOI: 10.1103/PhysRevResearch.4.033051