Precise determination of micromotion for trapped-ion optical clocks

Abstract

As relative systematic frequency uncertainties in trapped-ion spectroscopy are approaching the low 10 −18 range, motional frequency shifts account for a considerable fraction of the uncertainty budget. Micromotion, a driven motion fundamentally connected to the principle of the Paul trap, is a particular concern in these systems. In this article, we experimentally investigate at this level three common methods for minimizing and determining the micromotion amplitude. We develop a generalized model for a quantitative application of the photon-correlation technique, which is applicable in the commonly encountered regime where the transition linewidth is comparable to the rf drive frequency. We show that a fractional frequency uncertainty due to the 2nd-order Doppler shift below |∆ν/ν| = 1 × 10 −20 can be achieved. The quantitative evaluation is verified in an interleaved measurement with the conceptually simpler resolved sideband method. If not performed deep within the Lamb-Dicke regime, a temperature-dependent offset at the level of 10 −19 is observed in resolved sideband measurements due to sampling of intrinsic micromotion. By direct comparison with photoncorrelation measurements, we show that the simple to implement parametric heating method is sensitive to micromotion at the level of |∆ν/ν| = 1 × 10 −20 as well.

An optimized ion trap geometry to measure quadrupole shifts of 171 Yb + clocks

“…[32]. These three laser beams will be used for detecting the micromotions in all the three directions independently [46,47]. After studying a series of trap geometries, we found the diameters of the outer electrode have weak influence on Φ (k) which is below the accuracy that is expected from the machining tolerances.…”

Limits on gravitational Einstein equivalence principle violation from monitoring atomic clock frequencies during a year

“…Since optical clocks approach fractional accuracy of 10 −18 (see, e.g. [29][30][31][32]) further progress in limiting the gravity-dependent EEP violating interaction is possible. Many existing measurements can probably be used for this purpose if the date of the measurements is known.…”

Two-dimensional ion crystals in radio-frequency traps for quantum simulation

“…For several types of ion-trap experiments, even small amounts of micromotion can have significant harmful effects: it can lead to large systematic Doppler shifts in ion-based atomic clocks [44,45], and it can substantially reduce the fidelities of quantum gates during a quantum computation (in the absence of advanced micromotion-correcting protocols) [46,47]. Nevertheless, many successful experiments do not depend sensitively on micromotion amplitude [48][49][50][51][52], and ion Coulomb crystals of up to 10 5 − 10 6 particles have been confined in rf Paul traps [53,54].…”