We achieved a ⁸⁷Rb condensate of 4⨯10⁵ atoms in the F=2, m_F=2 state. We use a hybrid trap consisting of a single focused laser beam at 1064nm (dimple) in the horizontal direction and a quadrupole magnetic field. The dimple is vertically shifted with respect to the quadrupole center to avoid Majorana spin-flips. A first evaporation ramp with a microwave driving the (2,2) to (1,1) transition, is followed by an optical evaporation.

We report on the measurement of the scattering properties of ultracold ¹⁷⁴Yb bosons in a three-dimensional optical lattice. Site occupancy in an atomic Mott insulator is resolved with high-precision spectroscopy on an ultranarrow, metrological optical clock transition. Scattering lengths and loss rate coefficients for ¹⁷⁴Yb atoms in different collisional channels involving the ground state ¹S₀ and the metastable ³P₀ states are derived. These studies set important constraints for future experimental studies of two-electron atoms for quantum-technological applications

L. Franchi et al.,
State-dependent interactions in ultracold ¹⁷⁴Yb probed by optical clock spectroscopy
New J. Phys. 19, 103037 (2017)

Quantum phase slips, i.e., the primary excitations in one-dimensional superfluids at low temperature, have been well characterized in most condensed-matter systems, with the notable exception of ultracold quantum gases. Here we present our experimental investigation of the dissipation in one-dimensional Bose superfluids flowing along a periodic potential, which show signatures of the presence of quantum phase slips. In particular, by controlling the velocity of the superfluid and the interaction between the bosons we are apparently able to drive a crossover from a regime of thermal phase slips into a regime of quantum phase slips. Achieving a good control of quantum phase slips in ultracold quantum gases requires to keep under control other phenomena such as the breaking of superfluidity at the critical velocity or the appearance of a Mott insulator in the strongly correlated regime. Here we show our current results in these directions.

S. Scaffidi Abbate, et al.,
Exploring quantum phase slips in 1D bosonic systems
Eur. Phys. J. Spec. Top. 226, 2815 (2017)

We assembled a new vacuum system: a single 2D MOT for both the ⁸⁷Rb and ⁴¹K plus a 3D MOT where we plan to produce a “dimple trap” for the evaporation of the double species condensate. The chamber is provided with re-entrant viewports for high resolution optical access.

We explore the interplay between tunneling and interatomic interactions in the dynamics of a bosonic Josephson junction. We tune the scattering length of an atomic K39 Bose-Einstein condensate confined in a double-well trap to investigate regimes inaccessible to other superconducting or superfluid systems. In the limit of small-amplitude oscillations, we study the transition from Rabi to plasma oscillations by crossing over from attractive to repulsive interatomic interactions. We observe a critical slowing down in the oscillation frequency by increasing the strength of an attractive interaction up to the point of a quantum phase transition. With sufficiently large initial oscillation amplitude and repulsive interactions, the system enters the macroscopic quantum self-trapping regime, where we observe coherent undamped oscillations with a self-sustained average imbalance of the relative well population. The exquisite agreement between theory and experiments enables the observation of a broad range of many body coherent dynamical regimes driven by tunable tunneling energy, interactions and external forces, with applications spanning from atomtronics to quantum metrology.

G. Spagnolli, et al.,
Crossing Over from Attractive to Repulsive Interactions in a Tunneling Bosonic Josephson Junction
Phys. Rev. Lett. 118, 230403 (2017)