Improved Test of Local Lorentz Invariance from a Deterministic Preparation of Entangled States

TL;DR

This paper demonstrates that preparing entangled states of ext{Ca} ions significantly enhances the precision of tests for local Lorentz invariance of the electron, reaching quantum noise limits and surpassing previous bounds.

Contribution

The study experimentally shows how entanglement improves precision in fundamental symmetry tests, achieving quantum-limited measurements and setting new bounds for Lorentz invariance.

Findings

Entangled states reach quantum projection noise limit.

Achieved 2-4 times better bounds on Lorentz invariance.

Multipartite entanglement could further improve precision.

Abstract

The high degree of control available over individual atoms enables precision tests of fundamental physical concepts. In this Letter, we experimentally study how precision measurements can be improved by preparing entangled states immune to the dominant source of decoherence. Using \Ca ions, we explicitly demonstrate the advantage from entanglement on a precision test of local Lorentz invariance for the electron. Reaching the quantum projection noise limit set by quantum mechanics, we observe for bipartite entangled states the expected gain of a factor of two in the precision. Under specific conditions, multipartite entangled states may yield substantial further improvements. Our measurements improve the previous best limit for local Lorentz invariance of the electron using \Ca ions by factor of two to four to about $5\times10^{-19}$.