Spins in Cryogenic Quantum Solids: a new Platform for Hybrid Quantum Systems

Hybrid quantum systems offer a promising platform for studying quantum phenomena and developing next-generation quantum technologies, benefiting from the complementary strengths of their constituent components. Here, we introduce a novel hybrid quantum platform that integrates superconducting circuits with atomic impurities embedded in cryogenic inert-gas crystals. Unlike conventional solid-state hosts, these crystals provide a soft, inert, predominantly spin-0 environment, where virtually any atom, molecule, or radical can be hosted while preserving its quantum properties. As a proof of concept, we embed sodium atoms in neon crystals atop superconducting resonators and observe strong spin–photon coupling, spin lifetimes exceeding eight minutes, and coherence times up to 0.92 ms using Hahn echo pulse sequence. Importantly, the platform enables minimally invasive microwave-based probing and control, in contrast to traditional optical techniques that often introduce unwanted heating and excitation. These results establish doped cryogenic solids integrated with superconducting circuits as a versatile and high-coherence architecture for exploring fundamental quantum effects and advancing emerging quantum technologies.

A. Kanagin et al. arXiv:2508.21651