Production and detection of atomic hexadecapole at Earth's magnetic field

TL;DR

This paper demonstrates a novel method for producing and detecting atomic hexadecapole polarization at Earth's magnetic field, which is insensitive to nonlinear Zeeman effects and useful for improving atomic magnetometers.

Contribution

The authors develop a new technique for selective creation and detection of atomic hexadecapole moments in Earth's magnetic field, enhancing magnetometer accuracy.

Findings

Hexadecapole polarization is insensitive to nonlinear Zeeman effects.

The method enables long-lived ground-state hexadecapole polarization.

Experimental validation with $^{87}$Rb atoms at Earth's field.

Abstract

Anisotropy of atomic states is characterized by population differences and coherences between Zeeman sublevels. It can be efficiently created and probed via resonant interactions with light, the technique which is at the heart of modern atomic clocks and magnetometers. Recently, nonlinear magneto-optical techniques have been developed for selective production and detection of higher polarization moments, hexadecapole and hexacontatetrapole, in the ground states of the alkali atoms. Extension of these techniques into the range of geomagnetic fields is important for practical applications. This is because hexadecapole polarization corresponding to the $\Delta M=4$ Zeeman coherence, with maximum possible $\Delta M$ for electronic angular momentum $J=1/2$ and nuclear spin $I=3/2$, is insensitive to the nonlinear Zeeman effect (NLZ). This is of particular interest because NLZ normally leads to resonance splitting and systematic errors in atomic magnetometers. However, optical signals due to the hexadecapole moment decline sharply as a function of magnetic field. We report a novel method that allows selective creation of a macroscopic long-lived ground-state hexadecapole polarization. The immunity of the hexadecapole signal to NLZ is demonstrated with F=2 $^{87}$Rb atoms at Earth's field.