Measurement and simulation of atomic motion in nanoscale optical trapping potentials

TL;DR

This paper investigates the thermal motion of atoms trapped near nanofibers by using pulsed light to induce and monitor atomic wave packets, revealing oscillatory behavior and dephasing consistent with simulations.

Contribution

It introduces a novel method to measure atomic motion in nanofiber traps using short light pulses and compares results with Monte Carlo simulations.

Findings

Oscillation frequencies around 100 kHz

Motional dephasing occurs within 10 microseconds

Simulated temperatures between 25 and 40 microkelvin

Abstract

Atoms trapped in the evanescent field around a nanofiber experience strong coupling to the light guided in the fiber mode. However, due to the intrinsically strong positional dependence of the coupling, thermal motion of the ensemble limits the use of nanofiber trapped atoms for some quantum tasks. We investigate the thermal dynamics of such an ensemble by using short light pulses to make a spatially inhomogeneous population transfer between atomic states. As we monitor the wave packet of atoms created by this scheme, we find a damped oscillatory behavior which we attribute to sloshing and dispersion of the atoms. Oscillation frequencies range around 100 kHz, and motional dephasing between atoms happens on a timescale of 10 $\mu$s. Comparison to Monte Carlo simulations of an ensemble of 1000 classical particles yields reasonable agreement for simulated ensemble temperatures between 25 $\mu$K and 40 $\mu$K.