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arXiv:2608.03939 · Physical Review A

Enhanced coherence of rare-earth nuclear spins in a crystal

Bassam Nima, Yuiki Takahashi, Amar C. Vutha

Published Oct 27, 2026• 0 citations
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Abstract

Rare-earth ions in crystals are useful in precision measurements and quantum information science because of their exceptional optical and spin coherence properties. We show that the nuclear spin coherence time of $^{153}\mathrm{Eu}^{3+}$ ions doped into yttrium orthosilicate can be significantly enhanced by driving the environmental nuclear spins in the host crystal. This method of enhancing the spin coherence time can lead to improved precision measurements using rare-earth-doped crystals.

DOI
10.1103/s3dn-1wf7

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Rare-earth ions in crystals are useful in precision measurements and quantum information science because of their exceptional optical and spin coherence properties. We show that the nuclear spin coherence time of 153Eu3+^{153}\mathrm{Eu}^{3+}153Eu3+ ions doped into yttrium orthosilicate can be significantly enhanced by driving the environmental nuclear spins in the host crystal. This method of enhancing the spin coherence time can lead to improved precision measurements using rare-earth-doped crystals.
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In this paper, we present a method to investigate and control the dynamics of the nearby host nuclear spins (the 'frozen core') about a rare-earth ion doped in a crystal. Optically detected, double quantum magnetic resonance measurements were conducted on Eu 3+ Y 2 SiO 5 . The distinct magnetic resonant frequencies of nearby Y 3+ spins were measured along with the lifetime and coherence time of an individual Y 3+ spin. We demonstrate an entangling gate between the Eu 3+ spins and a Y 3+ spin associated with a particular position. Further, we propose a method to initialize the Y 3+ spin states, enabling the Y 3+ spins to be used as a quantum resource for quantum information applications.
Quantum light-matter interfaces connecting stationary qubits to photons will enable optical networks for quantum communications, precise global time keeping, photon switching and studies of fundamental physics. Rare-earth-ion-doped crystals are state-of-the-art materials for optical quantum memories and quantum transducers between optical photons, microwave photons and spin waves. Here we demonstrate coupling of an ensemble of neodymium rare-earth-ions to photonic nanocavities fabricated in the yttrium orthosilicate host crystal. Cavity quantum electrodynamics effects including Purcell enhancement (F=42) and dipole-induced transparency are observed on the highly coherent (4)I(9/2)-(4)F(3/2) optical transition. Fluctuations in the cavity transmission due to statistical fine structure of the atomic density are measured, indicating operation at the quantum level. Coherent optical control of cavity-coupled rare-earth ions is performed via photon echoes. Long optical coherence times (T2∼100 μs) and small inhomogeneous broadening are measured for the cavity-coupled rare-earth ions, thus demonstrating their potential for on-chip scalable quantum light-matter interfaces.
Atomic and atomlike defects in the solid state are widely explored for quantum computers, networks, and sensors. Rare earth ions are an attractive class of atomic defects that feature narrow spin and optical transitions that are isolated from the host crystal, allowing incorporation into a wide range of materials. However, the realization of long electronic spin coherence times is hampered by magnetic noise from abundant nuclear spins in the most widely studied host crystals. Here, we demonstrate that Er 3+ ions can be introduced via ion implantation into TiO 2, a host crystal that has not been studied extensively for rare earth ions and has a low natural abundance of nuclear spins. We observe efficient incorporation of the implanted Er 3+ into the Ti 4+ site (>50% yield) and measure narrow inhomogeneous spin and optical line widths (20 and 460 MHz, respectively) that are comparable to bulk-doped crystalline hosts for Er 3+ . This work demonstrates that ion implantation is a viable path to studying rare earth ions in new hosts and is a significant step toward realizing individually addressed rare earth ions with long spin coherence times for quantum technologies.