Micromotion minimisation by synchronous detection of parametrically excited motion

TL;DR

This paper introduces a method for detecting and compensating stray electric fields in ion traps by amplitude modulating the RF field, enabling precise micromotion minimization through synchronous detection of ion motion.

Contribution

The authors develop a novel technique using amplitude modulation near motional frequencies to detect stray fields with high sensitivity in ion trapping experiments.

Findings

Achieved sensitivity of 0.1 V/m/√Hz in stray field detection.

Demonstrated minimal uncertainty of 0.015 V/m in field compensation.

Method requires only a single laser beam for multi-directional field resolution.

Abstract

Precise control of charged particles in radio-frequency (Paul) traps requires minimising excess micromotion induced by stray electric fields. We present a method to detect and compensate such fields through amplitude modulation of the radio-frequency trapping field. Modulation at frequencies close to the motional modes of the trapped particle excites coherent motion whose amplitude linearly depends on the stray field. In trapped-ion experiments, this motion can be detected by recording the arrival times of photons scattered during laser cooling. Only a single laser beam is required to resolve fields in multiple directions. In a demonstration using a $^{88}\mathrm{Sr}^{+}$ ion in a surface electrode trap, we achieve a sensitivity of $0.1\, \mathrm{V}\, \mathrm{m}^{-1}\, /\, \sqrt{\mathrm{Hz}}$ and a minimal uncertainty of $0.015\, \mathrm{V}\, \mathrm{m}^{-1}$.