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Cold atoms prepared in the volume of a high-finesse optical resonator [1] form a hybrid quantum system that can serve as an interface between photonic and atomic qubits. Bistability in the hyperfine ground state of atoms [2] is useful for quantum sensing applications, while hybridized states of light and matter will be exploited in future quantum technology applications.
We experimentally demonstrate [3] strong collective coupling of the atoms to the cavity vacuum field by linear scattering from a transverse drive.
Arranging the atoms in an incommensurate lattice, with respect to the resonator mode, the scattering can be suppressed by destructive interference: resulting in a subradiant atomic array. We show however, that strong collective coupling leads to a drastic modification of the excitation spectrum, as evidenced by well-resolved vacuum Rabi splitting in the intensity of the fluctuations. Furthermore, we demonstrate a significant polarization rotation in the linear scattering off the subradiant array via Raman scattering induced by the strongly coupled vacuum field.
[1] D. Varga, B. Gábor, B. Sárközi, K.V. Adwaith, D. Nagy, A. Dombi, T.W. Clark, F.I.B. Williams, P. Domokos, A. Vukics: Loading atoms from a large magnetic trap to a small intra-cavity optical lattice, Phys. Lett. A 505, 129444 (2024).
[2] B. Gábor, D. Nagy, A. Vukics, P. Domokos: Quantum bistability in the hyperfine ground state of atoms, Phys. Rev. Research 5, L042038 (2023).
[3] B. Gábor, K. V. Adwaith, D. Varga, B. Sárközi, Á. Kurkó, A. Dombi, T. W. Clark, F. I. B. Williams, D. Nagy, A. Vukics, P. Domokos: Demonstration of strong coupling of a subradiant atom array to a cavity vacuum, arXiv:2408.17079 (2024).
