The work here takes an initial but important step towards reaching the ultimate limit of performance for strontium optical lattice clocks, where millions of atoms could be interrogated for coherence times greater than 100 s.
released from the crossed optical dipole trap. (B) Schematic showing propagation direction (large arrows) and polarization (double arrows) of the 3D lattice and clock laser beams. (C)Motional sideband spectroscopy using the oblique clock laser shows no observable red sidebands, illustrating that atoms are predominantly in the ground band of the lattice.
Optical lattice clocks have now entered the quantum degenerate regime. With atoms that are frozen into a 3D cubic lattice, we have advanced the state-of-the art in coherent atom-light interrogation times. Further improvements will be enabled by the next generations of ultra-stable optical reference cavities based on crystalline materials. The latest advances in the frequency references and local oscillators that together constitute atomic clocks will lead to a new era for clock performance, resulting in new measurement capabilities.
Quantum degenerate clocks also provide a promising platform for studying many-body physics. Future studies of dipolar interactions will not only be necessary for clock accuracy, but will also provide insight into long-range quantum spin systems in a regime distinct from those explored by polar molecules, Rydberg gases and highly magnetic atoms. When clocks ultimately confront the natural linewidth of the atomic frequency reference, degenerate Fermi gases may be useful for engineering longer coherence times through Pauli blocking of spontaneous emission or collective radiative effects. Ultracold quantum gases provide new capabilities for precision metrology.