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  • Open Access

Spin Squeezing with Itinerant Magnetic Dipoles

Alec Douglas*, Vassilios Kaxiras*, Lin Su, Michal Szurek, Vikram Singh, Ognjen Marković, and Markus Greiner

  • *These authors contributed equally to this work.
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Phys. Rev. X 15, 041021 – Published 5 November, 2025

DOI: https://doi.org/10.1103/shj7-9kb3

Abstract

Entanglement can improve the measurement precision of quantum sensors beyond the shot noise limit. Neutral atoms, the basis of some of the most precise and accurate optical clocks and interferometers, do not naturally exhibit the all-to-all interactions traditionally used to generate such entangled states. On the other hand, these systems exhibit exceedingly high degrees of experimental control over parameters such as temperature, spatial entropy, and itinerancy. In this work, we investigate spin squeezing in a highly coherent itinerant system of neutral atoms with magnetic dipole-dipole interactions. We achieve 7.1 dB of metrologically useful squeezing using finite-range spin-exchange interactions in an erbium quantum gas microscope, and we demonstrate that introducing atomic motion, realizing a dipolar t−J model, protects the spin sector coherence at low fillings, significantly improving the achievable spin squeezing in a 2D dipolar system. This work’s protocol can be implemented with most neutral atoms, opening the door to quantum-enhanced metrology in other itinerant dipolar systems, such as molecules or optical lattice clocks, and serves as a novel method for studying itinerant quantum magnetism with long-range interactions.

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Popular Summary

Quantum sensors such as atomic clocks and interferometers are already the most precise measurement devices in the world, but their performance can still be improved by using entanglement, a uniquely quantum effect that links particles in ways impossible for classical systems. The challenge is that neutral atoms, which form the basis of today’s best clocks, normally lack the right kind of interactions to generate entanglement. Our work shows how to overcome this limitation.

We use a quantum gas microscope with fermionic erbium atoms and take advantage of their natural magnetic dipole-dipole forces to create entangled states. This produces a state with a measurement variance about one-fifth that of any comparable classical ensemble. Surprisingly, we also find that letting the atoms move—by tunneling between sites in the optical lattice—helps preserve coherence and even enhances squeezing at low densities. What is usually thought of as noise instead becomes a useful resource when combined with long-range dipolar interactions.

Because our method relies only on ingredients available in many atomic and molecular systems, it can be broadly applied, from ultracold molecules to optical lattice clocks. This opens a practical path to quantum-enhanced metrology and new tests of fundamental physics. At the same time, it provides a platform for exploring new forms of quantum magnetism, where atomic motion and long-range interactions combine in unexpected ways.

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Phys. Rev. X 15, 041021– Published 5 November, 2025
  • Received 20 March 2025
  • Accepted 15 August 2025
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