Abstract
We introduce a scheme to coherently suppress second-rank tensor frequency shifts in atomic clocks, relying on the continuous rotation of an external magnetic field during the free atomic state evolution in a Ramsey sequence. The method retrieves the unperturbed frequency within a single interrogation cycle and is readily applicable to various atomic clock systems. For the frequency shift due to the electric quadrupole interaction, we experimentally demonstrate suppression by more than two orders of magnitude for the ^{2}S_{1/2}→^{2}D_{3/2} transition of a single trapped ^{171}Yb^{+} ion. The scheme provides particular advantages in the case of the ^{171}Yb^{+} ^{2}S_{1/2}→^{2}F_{7/2} electric octupole (E3) transition. For an improved estimate of the residual quadrupole shift for this transition, we measure the excited state electric quadrupole moments Θ(^{2}D_{3/2})=1.95(1)ea_{0}^{2} and Θ(^{2}F_{7/2})=-0.0297(5)ea_{0}^{2} with e the elementary charge and a_{0} the Bohr radius, improving the measurement uncertainties by one order of magnitude.
Highlights
The ever-increasing level of control over neutral atoms and ions provides rapid progress in their wide range of applications from quantum computing to high-precision frequency measurements
Accuracy and universality of atomic clocks are based on the concept of an unperturbed transition frequency, as observed under idealized conditions in the absence of systematic frequency shifts
Other systematic shifts can be eliminated by averaging the clock output frequency over a set of discrete experimental parameters that are used in alternating cycles of clock operation
Summary
Other systematic shifts can be eliminated by averaging the clock output frequency over a set of discrete experimental parameters that are used in alternating cycles of clock operation This includes probing different Zeeman components of the clock transition [7,8] and cycling between mutually orthogonal directions of an externally applied magnetic field defining the quantization axis [9]. We focus on frequency shifts produced by orientation-dependent interactions described by traceless symmetric second-rank tensors Common examples of such effects in atomic spectroscopy are the tensorial Stark effect, the quadrupole interaction with an electric field gradient, or the interaction between two magnetic dipoles. A related method is used in trapped-ion optical clocks for the elimination of shifts resulting from tensor interactions with
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