Atom interferometry with trapped samples offers the advantage of long interrogation times in compact setups, measuring forces and local fields with spatial resolution of a few micrometers. Here, we experimentally demonstrate a multimode interferometer comprising a Bose-Einstein condensate of ³⁹K atoms trapped in a harmonic potential, where the interatomic interaction is canceled exploiting Feshbach resonances. A pulsed optical lattice coherently splits the BEC in multiple momentum components (Kapitza-Dirac diffraction), that form different interferometric modes oscillating in the harmonic potential along separate trajectories. When these trajectories recombine after half- or full-oscillation period, a second Kapitza-Dirac diffraction reshuffles the momentum components, i.e. the interferometer modes: the relative modal amplitudes at the interferometer output are sensitive to external forces, through the induced displacement of the harmonic potential. We characterize the interferometer performance and discuss perspective improvements.

L. Masi et al.
Multimode trapped interferometer with noninteracting Bose-Einstein condensates
Phys. Rev. Research 3, 043188 (2021)

We realize a programmable quantum vortex collider in planar and homogeneous atomic Fermi superfluids with tunable inter-particle interactions. We follow a bottom-up approach reminiscent of other atomic platforms featuring control at the single-particle level, and gain exquisite control of individual 2D vortices to assemble them one by one in arbitrary arrangements. In particular, we use the combination of a high resolution microscope objective and a Digital Micromirror Device to create on-demand vortex configurations and we monitor their evolution across the BEC-BCS regimes of fermionic superfluidity. By engineering collisions within and between vortex–antivortex pairs we distinguish the different relaxation processes of the irrotational vortex energy due to sound emission and due to interactions with normal fluid. For the first time, we directly visualize how the annihilation of vortex dipoles radiates a sound pulse. We progress towards a complete microscopic description of the dissipative dynamics of both single and colliding vortex–antivortex pairs, which is at the heart of the relaxation of non-equilibrium states in bosonic and fermionic superfluids, thereby opening the route to exploring new pathways for quantum turbulence decay, vortex by vortex.

W. J. Kwon et al.
Sound emission and annihilations in a programmable quantum vortex collider
Nature 600, 64 (2021)

Happy to announce the first ion crystals of Ba+ observed in our unconventional ion trap. Congrats to all the people that worked on the project!

Cooling neutral atoms in optical traps can be a difficult task under some experimental conditions, like when optical trapping potentials are state-dependent. We report on a theoretical study showing that cooling can be achieved even if the internal states of the atoms experience different potential depths as long as a well-tailored frequency sweep is applied to the cooling laser. We develop a master rate equation and a Monte Carlo simulation for atoms of Li and Yb trapped in optical lattices and tweezers and we find that the average occupation number of the vibrational levels is drastically reduced under feasible experimental conditions. Our findings provide an alternative cooling scheme that can be applied in principle to any particle that is optically trappable, e.g. atoms, molecules or ions, and can provide a faster route to cooling atoms to condensation or degeneracy.

F. Berto, et al.
Prospects for single-photon sideband cooling of optically trapped neutral atoms
Phys. Rev. Research 3, 043106 (2021)

We report the experimental realization of a new kind of optical lattice for ultra-cold atoms where arbitrarily large separation between the sites can be achieved without renouncing to the stability of ordinary lattices. Two collinear lasers, with slightly different commensurate wavelengths and retrorefected on a mirror, generate a superlattice potential with a periodic \beat-note" profile where the regions with large amplitude modulation provide the effective potential minima for the atoms. To prove the analogy with a standard large spacing optical lattice we study Bloch oscillations of a Bose Einstein condensate with negligible interactions in the presence of a small force. The observed dynamics between sites separated by ten microns for times exceeding one second proves the high stability of the potential. This novel lattice is the ideal candidate for the coherent manipulation of atomic samples at large spatial separations and might find direct application in atom-based technologies like trapped atom interferometers and quantum simulators.

L. Masi, et al.,
Spatial Bloch Oscillations of a Quantum Gas in a “Beat-Note” Superlattice
Phys. Rev. Lett. 127, 020601 (2021)