Suppression of Collisional Shifts in a Strongly Interacting Lattice Clock

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Science  03 Feb 2011:
DOI: 10.1126/science.1196442


Optical lattice clocks have the potential for extremely high-frequency stability owing to the simultaneous interrogation of many atoms, but this precision may come at the cost of systematic inaccuracy resulting from atomic interactions. Density-dependent frequency shifts can occur even in a clock that uses fermionic atoms if they are subject to inhomogeneous optical excitation. However, sufficiently strong interactions can suppress collisional shifts in lattice sites containing more than one atom. We demonstrate the effectiveness of this approach with a Sr lattice clock by reducing both the collisional frequency shift and its uncertainty to the level of 10−17. This result eliminates the compromise between precision and accuracy in a many-particle system, as both will continue to improve with particle number.