In a paper recently published by the Physics Review, Shimon Kolkowitz and team explain how an atomic clock can be improved by splitting it up
Thanks to their remarkable precision and accuracy, optical atomic clocks are rapidly advancing the frontiers of timekeeping, quantum science, and fundamental physics. A critical figure of merit of an optical atomic clock is its instability, a measure of how rapidly the clock can reach a specific frequency precision given the noise it is subject to. Much research has therefore been devoted to reducing that noise by improving the optical cavities used to stabilize the clock laser or by introducing entangled atomic states to reduce the fundamental quantum noise associated with measuring the atoms in the clock. In this work, we demonstrate an alternative approach to reducing the instability of a strontium optical lattice atomic clock by making more efficient use of its atoms.
Strontium atoms in a magneto optical trap, in the Kolkowitz Lab
Standard atomic clocks treat all the atoms in the clock the same, measuring them all identically and at once. We show that by instead splitting the atoms up into multiple atomic ensembles that are spatially resolved and independently controlled, we can more precisely measure the frequency difference between the atomic transition and the clock laser. We demonstrate new techniques that make use of either two or four atomic ensembles to reduce the measured instability of the clock by up to a factor of 2 compared to an otherwise identical standard optical atomic clock with the same total number of atoms.
The techniques we demonstrate can be straightforwardly implemented in other existing optical atomic clocks, with comparable expected gains in clock performance.