Measuring the Angular Momentum of a Neutron Using Earth's Rotation

TL;DR

This study demonstrates the measurement of neutron orbital angular momentum via the Earth's rotation-induced Sagnac effect, achieving high precision and lower systematic errors, and opens pathways for future quantum angular momentum experiments.

Contribution

It introduces a novel method to measure neutron OAM using Earth's rotation, with improved accuracy and lower systematic errors compared to previous experiments.

Findings

Measured neutron OAM coupling within 5% of theory

Achieved transverse OAM detection of 4098 ± 295 hbar A-1

Demonstrated feasibility of using the Sagnac effect for neutron OAM measurement

Abstract

A coupling between Earths rotation and orbital angular momentum (OAM), known as the Sagnac effect, is observed in entangled neutrons produced using a spin echo interferometer. After correction for instrument systematics the measured coupling is within 5% of theory, with an uncertainty of 7.2%. The OAM in our setup is transverse to the propagation direction and scales linearly with wavelength (4 A - 12.75 A), hence the coupling can be varied, without mechanically rotating the device. Therefore, the systematic error is lower than in previous experiments. The detected transverse OAM of our beam corresponds to 4098 +- 295 hbar A-1, 5 orders of magnitude lower than in previous neutron experiments, thereby demonstrating the feasibility of using the Sagnac effect to definitively measure neutron OAM and paving the way towards observations of the quantum Sagnac effect