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 dipole trap arXiv:2310.04199 [quant-ph]
We show that an optimized loading of a cold ensemble of rubidium-87 atoms from a magnetic trap into an optical dipole trap sustained by a single, far-red-detuned mode of a high-Q optical cavity can be efficient despite the large volume mismatch of the traps. The magnetically trapped atoms are magnetically transported to the vicinity of the cavity mode and released from the magnetic trap in a controlled way meanwhile undergoing an evaporation period. Large number of atoms get trapped in the dipole potential for several hundreds of milliseconds. We monitor the number of atoms in the mode volume by a second tone of the cavity close to the atomic resonance. While this probe tone can pump atoms to another ground state uncoupled to the probe, we demonstrate state-independent trapping by applying a repumper laser.
Finite-size scaling of bistability curves to the thermodynamic limit. Atoms in an optical cavity can manifest a first-order dissipative phase transition where the stable coexisting phases are quantum states with high quantum purity. The figure shows the transmission of one of the modes of the cavity (a), the population of one of the hyperfine ground states of the atoms (b) and the population of the excited states (c) as a function of the ratio of the driving fields of the cavity modes (which is parametrized by an angle between 0 and π/2). Solid (dashed) lines correspond to stable (unstable) solutions. Approaching the thermodynamic limit (i. e. increasing the number of atoms) the switching between the stable phases become sharper and sharper, the bistable region spreads to all possible values of the control parameter, and the population of the excited states tends to 0.