Vectorial polaritons in the quantum motion of a levitated nanosphere
A. Ranfagni, Paolo Vezio, M. Calamai, Avishek Chowdhury, Francesco Marino, F. Marín
Abstract
The strong coupling between photons and bosonic excitations in matter produces hybrid quasiparticle states known as polaritons(1-3). Their signature is the avoided crossing between the eigenfrequencies of the coupled system illustrated by the Jaynes-Cummings Hamiltonian(4). It has been observed in quantum electrodynamics experiments based on atoms(5,6), ions(7), excitons(8-10), spin ensembles(11,12) and superconducting qubits(13). In cavity optomechanics, polariton modes originate from the quantum-coherent coupling of a macroscopic mechanical vibration to the cavity radiation field(14,15). Here we investigate polaritonic modes in the motion of an optically levitated nanosphere(16-22) in the quantum-coherent coupling regime. The particle is trapped in a high vacuum by an optical tweezer and strongly coupled to a single cavity mode by coherent scattering of the tweezer photons(23-27). The two-dimensional motion and optical cavity mode define an optomechanical system with three degrees of freedom. In the strong-coupling regime, we observe hybrid light-mechanical states with a vectorial nature. Our results pave the way towards protocols for quantum information transfer between photonic and phononic components and represent a step towards the demonstration of optomechanical entangled states at room temperature.