Direct observation of nonlocal fermion pairing in an attractive Fermi-Hubbard gas.

The Hubbard model of attractively interacting fermions provides a paradigmatic setting for fermion pairing. It features a crossover between Bose-Einstein condensation of tightly bound pairs and Bardeen-Cooper-Schrieffer superfluidity of long-range Cooper pairs, and a "pseudo-gap" region where pairs form above the superfluid critical temperature. We directly observe the nonlocal nature of fermion pairing in a Hubbard lattice gas, using spin- and density-resolved imaging of [Formula: see text]1000 fermionic potassium-40 atoms under a bilayer microscope.

Quantum register of fermion pairs.

Quantum control of motion is central for modern atomic clocks and interferometers. It enables protocols to process and distribute quantum information, and allows the probing of entanglement in correlated states of matter. However, the motional coherence of individual particles can be fragile to maintain, as external degrees of freedom couple strongly to the environment.

Doublon-Hole Correlations and Fluctuation Thermometry in a Fermi-Hubbard Gas.

We report on the single atom and single site-resolved detection of the total density in a cold atom realization of the 2D Fermi-Hubbard model. Fluorescence imaging of doublons is achieved by splitting each lattice site into a double well, thereby separating atom pairs. Full density readout yields a direct measurement of the equation of state, including direct thermometry via the fluctuation-dissipation theorem.

Observation of Laughlin states made of light.

Much of the richness in nature emerges because simple constituents form an endless variety of ordered states. Whereas many such states are fully characterized by symmetries, interacting quantum systems can exhibit topological order and are instead characterized by intricate patterns of entanglement. A paradigmatic example of topological order is the Laughlin state, which minimizes the interaction energy of charged particles in a magnetic field and underlies the fractional quantum Hall effect.

Interacting Floquet polaritons.

Ordinarily, photons do not interact with one another. However, atoms can be used to mediate photonic interactions, raising the prospect of forming synthetic materials and quantum information systems from photons. One promising approach combines highly excited Rydberg atoms with the enhanced light-matter coupling of an optical cavity to convert photons into strongly interacting polaritons.