Decoherence induced by dipole-dipole couplings between atomic species in rare-earth ion-doped Y$_2$SiO$_5$

TL;DR

This study explores how magnetic field parameters influence decoherence in rare-earth ion-doped crystals, identifying key mechanisms and optimal configurations to enhance quantum coherence times.

Contribution

It provides a theoretical and simulation-based analysis of magnetic dipole-dipole induced decoherence in rare-earth ions, extending understanding to low magnetic field regimes and different ion species.

Findings

Decoherence is strongly affected by magnetic field direction and amplitude.

Certain magnetic configurations can minimize dipole-dipole induced decoherence.

Simulations align well with experimental spin echo data.

Abstract

Rare-earth ion doped crystals are state-of-the-art platforms for processing quantum information, particularly thanks to their excellent optical and spin coherence properties at cryogenic temperatures. Experimental observations have shown that the application of a static magnetic bias field significantly improves the coherence times in the rare-earth ions ensemble, but only a few studies have focused on its the dependency as a function of both magnetic field direction and amplitude. This is especially true for magnetic field amplitudes under the mT, and for low magnetic dipole moment ions. In this paper, we investigate the relationship between the magnetic field parameters and the decoherence caused by magnetic dipole-dipole coupling with the nearest neighbors nuclear spins in the crystal. The primary non-Kramers rare-earth ions investigated here are europium and praseodymium, but we also extend our study to the ytterbium Kramers ion due to its low magnetic dipole in the mT range. We perform theoretical investigations and simulations of the energy structure and coherence time evolution and identify good correspondences between experimental and simulated spin echo data. This work allows us to pinpoint the most relevant decoherence mechanisms in the considered magnetic field regime, and to predict favorable magnetic configurations.