Evaluation of blackbody radiation shift with temperature associated fractional uncertainty at 10E-18 level for 40Ca+ ion optical clock

TL;DR

This study models and measures the temperature rise due to blackbody radiation in a calcium ion optical clock setup, achieving a fractional uncertainty at the 10^-18 level, crucial for high-precision timekeeping.

Contribution

The paper presents a validated finite-element model to accurately evaluate blackbody radiation effects and associated uncertainties in a calcium ion optical clock.

Findings

Temperature rise is 1.72 K with an uncertainty of 0.46 K.

Blackbody radiation contributes 2.2 mHz to systematic uncertainty.

Overall fractional uncertainty achieved is 5.4×10^-18.

Abstract

In this paper, blackbody radiation (BBR) temperature rise seen by the $^{40}$Ca$^+$ ion confined in a miniature Paul trap and its uncertainty have been evaluated via finite-element method (FEM) modelling. The FEM model was validated by comparing with thermal camera measurements, which were calibrated by PT1000 resistance thermometer, at several points on a dummy trap. The input modelling parameters were analyzed carefully in detail, and their contributions to the uncertainty of environment temperature were evaluated on the validated FEM model. The result shows that the temperature rise seen by $^{40}$Ca$^+$ ion is 1.72 K with an uncertainty of 0.46 K. It results in a contribution of 2.2 mHz to the systematic uncertainty of $^{40}$Ca$^+$ ion optical clock, corresponding to a fractional uncertainty 5.4$\times$10$^{-18}$. This is much smaller than the uncertainty caused by the BBR shift coefficient, which is evaluated to be 4.8 mHz and at 10$^{-17}$ level in fractional frequency units.