JILA, National Institute of Standards and Technology, and Department of Physics, University of Colorado, Boulder, CO 80309, USA.
Science. 2011 Feb 25;331(6020):1043-6. doi: 10.1126/science.1196442. Epub 2011 Feb 3.
Optical lattice clocks with extremely stable frequency are possible when many atoms are interrogated simultaneously, 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 demonstrated the effectiveness of this approach with a strontium 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; both will continue to improve as the number of particles increases.
当同时探测大量原子时，光学晶格钟可以获得极其稳定的频率，但这种精度可能会因原子相互作用而导致系统误差。即使在使用费米子原子的时钟中，如果它们受到非均匀光激发，也会发生依赖于密度的频率移动。然而，如果相互作用足够强，晶格中包含一个以上原子的位置的碰撞频移可以被抑制。我们通过将 Sr 晶格钟的碰撞频移及其不确定度降低到 10^(-17)的水平，证明了这种方法的有效性。这一结果消除了多粒子系统中精度和准确性之间的权衡取舍；随着粒子数量的增加，两者都将继续提高。
