Composite pulses for interferometry in a thermal cold atom cloud

TL;DR

This paper demonstrates that composite pulse techniques can significantly improve coherence and reduce errors in atom interferometry with thermal cold atom clouds, enhancing the sensitivity of quantum sensors.

Contribution

It applies and compares composite pulse sequences for velocity-sensitive Raman manipulation in thermal atom clouds, showing improved coherence and reduced infidelity.

Findings

Inversion infidelity halved in 80 μK atom cloud

Composite pulses improve coherence in thermal atom interferometry

Potential for larger interferometer areas and longer interaction times

Abstract

Atom interferometric sensors and quantum information processors must maintain coherence while the evolving quantum wavefunction is split, transformed and recombined, but suffer from experimental inhomogeneities and uncertainties in the speeds and paths of these operations. Several error-correction techniques have been proposed to isolate the variable of interest. Here we apply composite pulse methods to velocity-sensitive Raman state manipulation in a freely-expanding thermal atom cloud. We compare several established pulse sequences, and follow the state evolution within them. The agreement between measurements and simple predictions shows the underlying coherence of the atom ensemble, and the inversion infidelity in an 80 micro-Kelvin atom cloud is halved. Composite pulse techniques, especially if tailored for atom interferometric applications, should allow greater interferometer areas, larger atomic samples and longer interaction times, and hence improve the sensitivity of quantum technologies from inertial sensing and clocks to quantum information processors and tests of fundamental physics.