Enhancing collective spin squeezing via one-axis twisting echo control of individual atoms

TL;DR

This paper introduces a coherent control scheme that enhances collective spin squeezing in atomic ensembles by combining one-axis twisting interactions with an echo sequence, improving entanglement and state accessibility for quantum metrology.

Contribution

It proposes a novel protocol that boosts atom-atom entanglement and encodes it in two magnetic sublevels, simplifying state control for quantum-enhanced measurements.

Findings

Protocol effectively enhances spin squeezing via internal state manipulation.

Entanglement is mapped onto two magnetic sublevels suitable for metrology.

The approach offers a straightforward method for generating accessible entangled states.

Abstract

Spin squeezing generated via inter-atom entanglement in multilevel atomic ensembles provides a powerful resource for quantum-enhanced metrology. Existing schemes that harness internal atomic degrees of freedom to boost squeezing typically encode the collective squeezing in complex superpositions of magnetic sublevels, which complicates state control and limits practical applications. Here, we propose a coherent control scheme that simultaneously enhances collective spin squeezing and maps the resulting atom-atom entanglement onto two well-defined magnetic sublevels suitable for subsequent metrology experiments. Our protocol sandwiches a quantum non-demolition measurement between two internal one-axis-twisting interactions arranged in an echo sequence. We show that this approach can optimally leverage internal states to boost the inter-atom entanglement and, at the same time, encode it in two magnetic sublevels, which is readily convertible into metrologically useful spin squeezing. Our results offer a straightforward and efficient strategy for generating highly entangled yet readily accessible quantum states in multilevel atomic systems.