Optical clocks at sea.

Deployed optical clocks will improve positioning for navigational autonomy, provide remote time standards for geophysical monitoring and distributed coherent sensing, allow time synchronization of remote quantum networks and provide operational redundancy for national time standards. Although laboratory optical clocks now reach fractional inaccuracies below 10 (refs. ), transportable versions of these high-performing clocks have limited utility because of their size, environmental sensitivity and cost.

Spin-imbalance in a one-dimensional Fermi gas.

Superconductivity and magnetism generally do not coexist. Changing the relative number of up and down spin electrons disrupts the basic mechanism of superconductivity, where atoms of opposite momentum and spin form Cooper pairs. Nearly forty years ago Fulde and Ferrell and Larkin and Ovchinnikov (FFLO) proposed an exotic pairing mechanism in which magnetism is accommodated by the formation of pairs with finite momentum.

Pairing and phase separation in a polarized Fermi gas.

We report the observation of pairing in a gas of atomic fermions with unequal numbers of two components. Beyond a critical polarization, the gas separates into a phase that is consistent with a superfluid paired core surrounded by a shell of normal unpaired fermions. The critical polarization diminishes with decreasing attractive interaction.

Conversion of an atomic Fermi gas to a long-lived molecular Bose gas.

We have converted an ultracold Fermi gas of 6Li atoms into an ultracold gas of 6Li2 molecules by adiabatic passage through a Feshbach resonance. Approximately 1.5 x 10(5) molecules in the least-bound, v=38, vibrational level of the X1Sigma(+)(g) singlet state are produced with an efficiency of 50%.

Formation and propagation of matter-wave soliton trains.

Attraction between the atoms of a Bose-Einstein condensate renders it unstable to collapse, although a condensate with a limited number of atoms can be stabilized by confinement in an atom trap. However, beyond this number the condensate collapses. Condensates constrained to one-dimensional motion with attractive interactions are predicted to form stable solitons, in which the attractive forces exactly compensate for wave-packet dispersion.