Scaling trapped-ion clocks to tens of ions while maintaining 10<sup>-19</sup>-level systematic uncertainties
ORAL · Invited
Abstract
Trapped ions offer an exceptional level of experimental control, which enables systematic clock uncertainties in the 10-19 range and high-fidelity quantum state manipulation. Besides fundamental research, frequency metrology in this regime supports new applications - such as geodetic measurements with sub-cm resolution of the gravitational potential - which will also benefit from the miniaturization capabilities of ion trap technology.
At this level of accuracy, frequency measurements are increasingly limited by their statistical uncertainty, even after months of averaging time. Scaling from single ions to ensembles (Coulomb crystals) improves the signal-to-noise ratio and is the prerequisite for quantum-enhanced interrogation protocols, but maintaining low systematic uncertainties in the process has long been considered challenging.
We present clock operation with a 20-ion chain, containing eight 115In+ ions sympathetically cooled by 172Yb+. The overall systematic uncertainty due to experimental conditions is evaluated to be 7 x 10-19, while to-be-determined atomic properties add a constant offset currently known to within 1.7 x 10-18. By performing differential clock ion comparisons within the chain, we experimentally bound spatial inhomogeneities with a statistical uncertainty of 2 x 10-18.
An investigation of measurement noise demonstrates the expected reduction of the statistical uncertainty with ion number, resulting in an instability of 5 x 10-16 / √t (sufficient, e.g., to resolve daily tides on a continental scale). Based on these measurements, we analyze the scaling of statistical and systematic uncertainty under realistic conditions and present the prospect for further increases in clock ion number and uncertainties in the low 10-19 range.
At this level of accuracy, frequency measurements are increasingly limited by their statistical uncertainty, even after months of averaging time. Scaling from single ions to ensembles (Coulomb crystals) improves the signal-to-noise ratio and is the prerequisite for quantum-enhanced interrogation protocols, but maintaining low systematic uncertainties in the process has long been considered challenging.
We present clock operation with a 20-ion chain, containing eight 115In+ ions sympathetically cooled by 172Yb+. The overall systematic uncertainty due to experimental conditions is evaluated to be 7 x 10-19, while to-be-determined atomic properties add a constant offset currently known to within 1.7 x 10-18. By performing differential clock ion comparisons within the chain, we experimentally bound spatial inhomogeneities with a statistical uncertainty of 2 x 10-18.
An investigation of measurement noise demonstrates the expected reduction of the statistical uncertainty with ion number, resulting in an instability of 5 x 10-16 / √t (sufficient, e.g., to resolve daily tides on a continental scale). Based on these measurements, we analyze the scaling of statistical and systematic uncertainty under realistic conditions and present the prospect for further increases in clock ion number and uncertainties in the low 10-19 range.
*This work has been partly supported by the project 23FUN03 HIOC, which has received funding from the European Partnership on Metrology, co-financed from the European Union's Horizon Europe Research and Innovation Programme and by the Participating States. We acknowledge funding by Deutsche Forschungsgemeinschaft (DFG) under Germany's Excellence Strategy - EXC-2123 QuantumFrontiers - 390837967 (RU B06) and through Grant No. CRC 1227 (DQ-mat, project B03).
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Presenters
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Jonas Keller
- Physikalisch-Technische Bundesanstalt