Optical lattice clocks have demonstrated unprecedented performance below the 10^-18 fractional level, advancing towards new standards of timekeeping and sensitive probes in fundamental physics. To further advance optical lattice clocks performance, it is crucial to attain lower temperatures which facilitates the use of shallow lattices with reduced light shifts, while retaining large atom numbers to reduce the quantum projection noise. Here, we present Sisyphus cooling using the long-lived 3P0 clock state in alkaline-earth-like ytterbium. Upon excitation on the ultranarrow clock transition, Sisyphus cooling is observed within a spatially periodic potential induced by a 1388-nm optical standing wave that is nearly resonant with the 3P0 → 3D1 transition. Our cooling demonstrates versatility, working both in free space and in a magic-wavelength lattice. It offers the flexibility of being employed in either pulsed or continuous modes, making it suitable to a range of quantum metrology applications.
Ethan Clements, Matthew Bohman, May Kim, Kaifeng Cui, Aaron Hankin, Samuel Brewer, Jose Valencia, Chin-wen Chou, William McGrew, Nicholas Nardelli, Youssef Hassan, Xiaogang Zhang, Holly Leopardi, Tara Fortier, Andrew Ludlow, David Hume, David Leibrandt
Laser noise usually limits the stability of optical frequency ratio measurements, limiting the speed and precision one can compare two atomic frequency standards. In this talk I will describe two methods, correlation and differential spectroscopy, which utilize correlations in laser noise to increase the achievable interrogation time and thus increase the frequency comparison stability. Correlation spectroscopy is a technique which uses a parity measurement following a synchronized Ramsey interrogation to measure the relative frequency of two similar frequency atomic clocks. With this technique we achieve a measurement instability of (4×10^(-16))⁄√(τ⁄s) for a comparison of two single 27Al+ ion clocks. Differential spectroscopy uses an atomic clock with low projection noise, here a 171Yb lattice clock, to correct the phase noise of a second, higher frequency clock’s local oscillator thereby reducing the measurement instability to the level of the first. This can be further extended using two lattice clocks in a zero dead time configuration to correct the phase noise beyond the interrogation time reachable for a single Yb lattice clock. With these techniques we achieve measurement stabilities of (2.5×10^(-16))⁄√(τ⁄s) and (2×10^(-16))⁄√(τ⁄s) for a comparison between a single 27Al+ ion clock and a 171Yb lattice clock running as single clock and in a zero dead time configuration respectively. In addition to these techniques, I will also discuss recent progress towards characterizing the systematics of the NIST 40Ca+/27Al+ optical atomic clock.
Recent results from the JILA 87Sr optical lattice clock are presented. Using the tight confinement of an optical lattice in
combination wit a sub-Hz linewidth diode laser we have achieved a pulse-length limited linewidth of 1.8 Hz for the 1S0-
3P0 clock transition. This corresponds to a quality factor of Q ≈ 2.4 x 1014, and is a record for coherent spectroscopy.
With the addition of a small magnetic bias field, the high line Q of the clock transition has also allowed us to resolve the
nuclear-spin sublevels, and make a precision measurement of the differential Landé g-factor between the 1S0 and 3P0. We
present the current accuracy and stability of the lattice clock, and in addition, we report on our development of precision
tools for the lattice clock, including a stabilized clock laser, fs-comb based technology allowing accurate clock
comparison in both the microwave and optical domains, and clock transfer over an optical fiber in an urban environment.
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