Interferometric Quantum Scattering in a Juggling Atomic Clock

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This experimental research program will precisely study quantum scattering of ultracold cesium atoms in an atomic clock that juggles clouds of atoms. The group has recently demonstrated a fundamentally new type of scattering experiment in which a cesium atom, prepared in a superposition two states, scatters off of atoms in another cloud launched in the atomic clock. Each state of the superposition experiences a scattering phase shift, a measure of the strength of the interaction between the atoms. By detecting only the scattered part of each atom's wave function, the difference of the scattering phase shifts is directly observed as a frequency shift of the clock. A unique feature of this technique is that the frequency shift is independent of the atomic density. The technique allows scattering measurements with atomic-clock-like accuracy. Measurements of atomic scattering lengths with unprecedented accuracy are expected. They will precisely study the scattering of the different ground-substates of cesium atoms as a function of collision energy and magnetic field to unambiguously constrain ultracold cesium-cesium interactions. They will measure threshold effects and try to identify Feshbach and shape resonances. They can also probe the frequency shifts due to juggling collisions, important for improving the stability of future clocks. Highly precise measurements of scattering phase shifts near a narrow Feshbach resonance may stringently constrain the time variation of fundamental constants, such as the electron-proton mass ratio.Broader impacts of this program include the training of graduate students and postdoctoral researchers in many areas of modern technology from lasers, electro-optics, radio-frequency and microwave techniques, ultra-high vacuum, and atomic clocks and frequency control. This group has significantly contributed to the development of atomic clocks, including laser-cooled rubidium clocks, space clock design, juggling atomic fountains, ultra-stable lasers for optical frequency clocks, and studies of microwave cavities and cold collisions. The proposed research will lead to higher accuracy and stability of the cesium clocks that realize the definition of the SI second. The work will impact the understanding of ultracold atom-atom interactions with a breakthrough in clarity and precision.