Cavity-assisted preparation and detection of a unitary Fermi gas

Abstract

We report on the fast production and weakly destructive detection of a Fermi gas with tunable interactions in a high finesse cavity. The cavity is used both with far off-resonant light to create a deep optical dipole trap, and with near-resonant light to reach the strong light-matter coupling regime. The cavity-based dipole trap allows for an efficient capture of laser-cooled atoms, and the use of a lattice-cancellation scheme makes it possible to perform efficient intra-cavity evaporative cooling. After transfer in a crossed optical dipole trap, we produce deeply degenerate unitary Fermi gases with up to 7 • 10 5 atoms inside the cavity, with an overall 2.85 s long sequence. The cavity is then probed with near-resonant light to perform five hundred-times repeated, dispersive measurements of the population of individual clouds, allowing for weakly destructive observations of slow atom-number variations over a single sample. This platform will make possible the real-time observation of transport and dynamics as well as the study of driven-dissipative, strongly correlated quantum matter.

Universal pair-polaritons in a strongly interacting Fermi gas

“…We produce a quantum degenerate, strongly interacting Fermi gas of 6 Li following the method described in [37]. Atoms captured in a magneto-optical trap are first transferred into a standing wave optical dipole trap at 1064 nm created by the TEM 01 mode of the cavity.…”

“…We observe a decrease of Ω/2π from 26 to 20 MHz over the 50 consecutive measurements, and a decrease of δ by 27% over the consecutive measurements, the latter reflecting atom losses. About half of these losses can be attributed to the finite lifetime of the cloud [37]. The measurement-induced atom losses are thus 1.9(1) × 10 3 atoms per sweep, 0.2% of the initial atom number.…”

Tracking evaporative cooling of a mesoscopic atomic quantum gas in real time

“…The enhanced atom-light interaction in high-finesse optical cavities [9] provides a means for performing minimally invasive, extremely sensitive measurements on atomic gases. Demonstrations span from recording transient signals of single or few atoms passing through an optical cavity [10,11] to measurements on static and dynamically evolving mesoscopic trapped atomic ensembles [12][13][14][15][16][17], or the probing of dynamical evolution of novel states of matter realized in the cavity [18][19][20]. Dispersive atom-number readout, with precision below atomic shot noise and sensitivity reaching down to the single-atom level in mesoscopic ensembles [13], makes cavity-aided measurements particularly interesting for non-invasive dynamical transport measurements in cold gases [21][22][23].…”