Atom interferometers take advantage of the wave nature of atoms to measure fundamental constants and forces and may find use for sensing applications. The past two decades have seen a small but dedicated effort to improve their performance as gravity probes. So far, this has been limited by the time it takes for the atoms being probed by the interferometric measurement to drop down the measurement tower — typically a couple of seconds.
Victoria Xu and colleagues have now presented an order of magnitude improvement in this interrogation time, by using an optical trapping technique that allows them to measure gravitational potentials while holding, rather than dropping, atoms for up to 20 seconds. They thus reduced the dominant noise source of such measurements — the phase variance due to laboratory vibrations — by nearly four orders of magnitude, thereby drastically improving the precision of atom interferometers and opening up opportunities for fundamental tests of general relativity and measurements of other fundamental potentials.
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Taroni, A. Hold my gravimeter. Nat. Phys. 15, 1210 (2019). https://doi.org/10.1038/s41567-019-0751-x