Fountains of time: Tossing cold atoms like confetti, atomic‐fountain clocks launch a new era in timekeeping

Jennifer Sebby-Strabley

Andr  Clairon, Philippe Laurent, A. Nadir +4 more

Ben Lewis, Rachel Elvin, Aidan S. Arnold +2 more

Cold atom fountain clocks provide exceptional long term stability as they increase interrogation time at the expense of a larger size. We present a compact cold atom fountain using a grating magneto-optical trap to laser cool and launch the atoms in a simplified optical setup. The fountain is evaluated using coherent population trapping and demonstrates improved single-shot stability from the launch. Ramsey times up to 100 ms were measured with a corresponding fringe linewidth of 5 Hz. This technique could improve both short- and long-term stabilities of cold atom clocks while remaining compact for portable applications.

Stella Müller, Aida Bebeachibuli, Renato Ferracini Alves +3 more

Yao Li, Zhiyi Liu, Yu Hu +4 more

We propose a method for precise control of the launch velocity vector of a cold atomic cloud. By independently adjusting the relative detuning of three pairs of orthogonal counter-propagating laser beams in moving optical molasses, this method achieves accurate regulation of three-dimensional velocity components, thereby realizing precise calibration of atomic launch direction. It can significantly reduce the complexity of mechanical adjustments and mitigate residual errors caused by mechanical tuning, with the advantages of simplicity and easy implementation. Experimental verification on an 87Rb atomic fountain clock shows that the spatial distribution of the cold atomic cloud is obtained via horizontal velocity scanning, and the tilt deviation of the fountain clock is evaluated and corrected. Ultimately, the angles between the cold atom launch direction, the central axis of the fountain clock, and the vertical direction are all less than 0.1 mrad. Time-of-flight signal analysis indicates that under 3% laser power fluctuation, the long-term instability (5000 s) of the velocity reaches 62 μm/s. This method holds significant application value for atomic fountains, atomic gravimeters, atomic gyroscopes, and other cold atomic precision instruments based on moving molasses.