Cavity-mediated coherence protection and one-axis twisting for spins in solids

TL;DR

This paper demonstrates cavity-mediated collective interactions in a solid-state ensemble of Yb$^{3+}$ ions, leading to superradiance, spin squeezing, and extended coherence times, with implications for quantum technologies.

Contribution

It reports the first realization of cavity-mediated all-to-all interactions in a solid-state ensemble, enabling superradiance, spin squeezing, and coherence protection.

Findings

Observed superradiant emission on resonance.

Demonstrated unitary one-axis twisting dynamics.

Extended Ramsey coherence time from microseconds to milliseconds.

Abstract

Long-range interactions between emitters give rise to collective phenomena, including superradiance, spin squeezing, and coherence protection, that are important to both fundamental physics and quantum technologies. Despite progress in cold atoms, coherent cavity-mediated all-to-all interactions have not yet been realized in a solid-state ensemble. Here we demonstrate such interactions in a $^{171}$Yb$^{3+}$:CaWO$_4$ crystal coupled to a microwave resonator, observing superradiant emission on resonance and unitary one-axis twisting dynamics in the dispersive regime. The same interaction also opens a many-body energy gap that suppresses inhomogeneous dephasing, extending the ensemble Ramsey coherence time from tens of microseconds to milliseconds without decoupling pulses. These results establish a solid-state platform for collective many-body physics with direct implications for quantum technologies. Specifically, the observed one-axis twisting dynamics opens a path towards spin squeezing for entanglement-enhanced quantum metrology, and the extended coherence due to gap-protection is relevant for both microwave photon storage and precision measurement.