On-chip photon-pair generation in a silica microtoroidal cavity.

Microcavities with high Q factor and small mode volume have the potential to be efficient and compact sources of photon pairs. Here, we demonstrate on-chip photon-pair generation by spontaneous four-wave mixing in a silica microtoroidal cavity and obtain a coincidence-to-accidental ratio of 7.4 ± 0.

Engineering Quantum States of Matter for Atomic Clocks in Shallow Optical Lattices.

We investigate the effects of stimulated scattering of optical lattice photons on atomic coherence times in a state-of-the art ^{87}Sr optical lattice clock. Such scattering processes are found to limit the achievable coherence times to less than 12 s (corresponding to a quality factor of 1×10^{16}), significantly shorter than the predicted 145(40) s lifetime of ^{87}Sr's excited clock state. We suggest that shallow, state-independent optical lattices with increased lattice constants can give rise to sufficiently small lattice photon scattering and motional dephasing rates as to enable coherence times on the order of the clock transition's natural lifetime.

Emergence of multi-body interactions in a fermionic lattice clock.

Alkaline-earth atoms have metastable 'clock' states with minute-long optical lifetimes, high-spin nuclei and SU(N)-symmetric interactions, making them powerful platforms for atomic clocks, quantum information processing and quantum simulation. Few-particle systems of such atoms provide opportunities to observe the emergence of complex many-body phenomena with increasing system size. Multi-body interactions among particles are emergent phenomena, which cannot be broken down into sums over underlying pairwise interactions.

Imaging Optical Frequencies with 100 μHz Precision and 1.1 μm Resolution.

We implement imaging spectroscopy of the optical clock transition of lattice-trapped degenerate fermionic Sr in the Mott-insulating regime, combining micron spatial resolution with submillihertz spectral precision. We use these tools to demonstrate atomic coherence for up to 15 s on the clock transition and reach a record frequency precision of 2.5×10^{-19}.

A Fermi-degenerate three-dimensional optical lattice clock.

Strontium optical lattice clocks have the potential to simultaneously interrogate millions of atoms with a high spectroscopic quality factor of 4 × 10 Previously, atomic interactions have forced a compromise between clock stability, which benefits from a large number of atoms, and accuracy, which suffers from density-dependent frequency shifts. Here we demonstrate a scalable solution that takes advantage of the high, correlated density of a degenerate Fermi gas in a three-dimensional (3D) optical lattice to guard against on-site interaction shifts. We show that contact interactions are resolved so that their contribution to clock shifts is orders of magnitude lower than in previous experiments.