Optical clock comparison test of Lorentz symmetry

TL;DR

This study uses highly precise optical clocks to test Lorentz symmetry, finding no violations and setting new stringent limits on potential symmetry-breaking effects in electrons.

Contribution

First experimental demonstration of two single-ion clocks agreeing at the 10^{-18} level over half a year, testing Lorentz symmetry with unprecedented precision.

Findings

No sidereal modulations detected at the 10^{-19} level

Set new limits on Lorentz violation parameters for electrons

Improved previous bounds by two orders of magnitude

Abstract

Questioning the presumably most basic assumptions about the structure of space and time has revolutionized our understanding of Nature. State-of-the-art atomic clocks make it possible to precisely test fundamental symmetry properties of spacetime, and search for physics beyond the standard model at low energy scales of just a few electron volts. Here, we experimentally demonstrate for the first time agreement of two single-ion clocks at the $10^{-18}$ level and directly confirm the validity of their uncertainty budgets over a half-year long comparison period. The two clock ions are confined in separate ion traps with quantization axes aligned along nonparallel directions. Hypothetical Lorentz symmetry violations would lead to sidereal modulations of the frequency offset. From the absence of such modulations at the $10^{-19}$ level we deduce stringent limits on Lorentz symmetry violation parameters for electrons in the range of $10^{-21}$, improving previous limits by two orders of magnitude.