Identifying Candidate Hosts for Er³⁺ Spin-Qubits with Long Coherence Time

Spin-photon interfaces operating at telecom wavelengths are essential for scalable quantum networks. Among solid-state emitters, erbium ions (Er³⁺) are particularly promising, as they combine a spin-½ electronic ground state with an optical transition near 1.5 μm in the telecom C-band. However, identifying host materials that maintain long spin and optical coherence times remains a key challenge.

We present a high-throughput computational framework that screens Er-containing hosts for long spin-coherence times (T₂) and telecom-band addressability. The workflow integrates materials informatics filters on stoichiometry, site symmetry, band gap, and chemical compatibility with cluster correlation expansion simulations [1] that capture decoherence from nuclear spin baths, Er-Er dipolar interactions from dopants, and other electronic spins with g ≈ 2. The framework automatically builds isotope-aware bath models, samples inequivalent substitutional sites, and predicts trends in coherence times.

Our results yield design rules favoring wide band gap hosts, high-symmetry sites, low nuclear-spin density, weak site multiplicity, and controlled Er concentration, producing ranked oxide and fluoride, polycrystalline ceramics, and rare-earth stoichiometric crystals as promising hosts for coherent quantum networks.