Enhanced squeezing of a collective spin via control of its qudit subsystems

TL;DR

This paper demonstrates how controlling qudit subsystems in atomic ensembles enhances collective spin squeezing, leading to significant improvements in quantum metrology by optimizing entanglement and mitigating decoherence effects.

Contribution

It introduces a method to enhance spin squeezing through unitary control of atomic qudits, combining state preparation and internal spin squeezing for improved quantum measurement precision.

Findings

Achieved approximately 10 dB improvement in spin squeezing.

Showed that preparing states with large quantum fluctuations enhances entanglement.

Analyzed tradeoffs between entanglement enhancement and decoherence effects.

Abstract

Unitary control of qudits can improve the collective spin squeezing of an atomic ensemble. Preparing the atoms in a state with large quantum fluctuations in magnetization strengthens the entangling Faraday interaction. The resulting increase in interatomic entanglement can be converted into metrologically useful spin squeezing. Further control can squeeze the internal atomic spin without compromising entanglement, providing an overall multiplicative factor in the collective squeezing. We model the effects of optical pumping and study the tradeoffs between enhanced entanglement and decoherence. For realistic parameters we see improvements of ~10 dB.