Quantum ground-state cooling of two librational modes of a nanorotor

Author(s): Stephan Troyer, Florian Fechtel, Lorenz Hummer, Henning Rudolph, Benjamin A. Stickler, Uroš Delić, Markus Arndt
Abstract: Controlling the motion of nanoscale objects at the quantum limit promises opportunities to test fundamental quantum physics and advances in quantum sensing. Rotational motion is of particular interest, as its nonlinear dynamics in a compact, closed configuration space provides access to phenomena such as rotational interferometry, tunnelling between angular configurations and quantum-enhanced torque sensing. A key requirement for such experiments is the capability to trap nanorotors and cool their orientation close to the two-dimensional librational quantum ground state. When rotational motion is confined in a harmonic potential, it becomes librational. Here we demonstrate that coherent scattering into a high-finesse cavity enables the ground-state cooling of two orthogonal librational modes of an optically levitated SiO2 nanoparticle. Using a laser-induced desorption loading technique, we trap and cool several dimers and trimers of silica nanospheres to their respective ground states, all within a single day. The simultaneous cooling of both librational degrees of freedom allows us to align an individual nanorotor with respect to a space-fixed axis with an angular precision better than 20 µrad—close to the quantum-mechanical zero-point fluctuations.
Organisation(s): Quantum Optics, Quantum Nanophysics and Quantum Information
External organisation(s): Universität Duisburg-Essen, Universität Ulm, Technische Universität Wien
Journal: Nature Physics
No. of pages: 15
ISSN: 1745-2473
DOI: https://doi.org/10.48550/arXiv.2509.13398
Publication date: 04-2026
Peer reviewed: Yes
Austrian Fields of Science 2012: 103025 Quantum mechanics, 103026 Quantum optics
ASJC Scopus subject areas: General Physics and Astronomy
Portal url: https://ucrisportal.univie.ac.at/en/publications/55b63c1a-2701-45ea-b0ab-99336e1d164e