Making optical atomic clocks more stable with 10−1610^{-16} level laser stabilization

The superb precision of an atomic clock is derived from its stability. Atomic clocks based on optical (rather than microwave) frequencies are attractive because of their potential for high stability, which scales with operational frequency. Nevertheless, optical clocks have not yet realized this vast potential, due in large part to limitations of the laser used to excite the atomic resonance. To address this problem, we demonstrate a cavity-stabilized laser system with a reduced thermal noise floor, exhibiting a fractional frequency instability of $2 \times 10^{-16}$. We use this laser as a stable optical source in a Yb optical lattice clock to resolve an ultranarrow 1 Hz transition linewidth. With the stable laser source and the signal to noise ratio (S/N) afforded by the Yb optical clock, we dramatically reduce key stability limitations of the clock, and make measurements consistent with a clock instability of $5 \times 10^{-16} / \sqrt{\tau}$

Simultaneous remote transfer of accurate timing and optical frequency over a public fiber network

In this work we demonstrate for the first time that it is possible to transfer simultaneously an ultra-stable optical frequency and a precise and accurate timing over 540 km using a public telecommunication optical fiber networks with Internet data. The optical phase is used to carry both the frequency information and the timestamps by modulating a very narrow optical carrier at 1.55 µm with spread spectrum signals using two-way satellite time transfer modems. The results in term of absolute time accuracy (250 ps) and long-term timing stability (20 ps) well outperform the conventional Global Navigation Satellite System or geostationary transfer methods

Production of Feshbach molecules induced by spin-orbit coupling in Fermi gases

The search for topological superconductors is a challenging task1,2. One of the most promising directions is to use spinorbit coupling through which an s-wave superconductor can induce unconventional p-wave pairing in a spin-polarized metal3,4. Recently, synthetic spin-orbit couplings have been realized in cold-atom systems5-16 where instead of a proximity effect, s-wave pairing originates from a resonant coupling between s-wave molecules and itinerant atoms17. Here we demonstrate a dynamic process in which spin-orbit coupling coherently produces s-wave Feshbach molecules from a fully polarized Fermi gas, and induces a coherent oscillation between these two. This demonstrates experimentally that spin-orbit coupling does coherently couple singlet and triplet states, and implies that the bound pairs of this system have a triplet p-wave component, which can become a topological superfluid by further cooling to condensation and confinement to one dimension.link_to_subscribed_fulltex