Zeyang Xue

We demonstrate high-resolution in situ imaging of density-wave ordering induced by cavity-mediated interactions in a unitary Fermi gas. We observe long-range spatial correlations throughout the formation of density waves, both for adiabatic preparation and following a quench, with a pattern controlled by the cavity mode structure. Our single-shot microscopic images together with the real-time readout of the cavity photons provide access to atom-photon correlations. We use this capability to investigate order fluctuations as a function of time following a quench and to directly confirm the correspondence between optical and atomic observables. Our system opens rich perspectives, from local patterning to correlation measurements in long-range interacting quantum gases.

We describe the design and operation of a high-stability Fabry–Pérot cavity, for laser stabilization in cavity quantum-electrodynamics experiments. Our design is based on an inexpensive and readily available uniaxial carbon-fiber reinforced polymer tube spacer, featuring an ultra-low thermal expansion coefficient. As a result, our 136 mm-long cavity, which has a finesse of 5160, shows a coefficient of thermal expansion of 1.6 × 10−6 K−1. Enclosing it in a hermetic chamber at room-pressure and using simple temperature stabilization, we observe absolute frequency excursions over a full day below 50 MHz for a laser operating at 446.785 THz. The frequency stability is limited by the imperfect thermal isolation from the environment and can be corrected using a built-in piezoelectric actuator. In addition, we discuss a different variant of this design and identify future improvements. Our system provides a cost-effective and robust solution for transferring laser stability over different wavelengths, as well as for linewidth reduction or spectral filtering of CW laser sources for applications in quantum science.