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arXiv · 2603.01987

Cavity-enhanced optical readout and control of nuclear spin qubits

Alexander Ulanowski·Johannes Früh·Fabian Salamon·Adrian Holzäpfel·Andreas Reiserer
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Abstract

Their exceptional coherence makes nuclear spins in solids a prime candidate for quantum memories in quantum networks and repeaters. Still, the direct all-optical initialization, coherent control, and readout of individual nuclear spin qubits have been an outstanding challenge. Here, this is achieved by embedding 167-Er dopants in yttrium orthosilicate in a cryogenic Fabry-Perot cavity, whose linewidth of 65 MHz is much smaller than the 0.9 GHz separation of neighboring hyperfine levels. Frequency-selective emission enhancement thus enables a single-shot readout fidelity of 91(2)%. Furthermore, a large magnetic field freezes paramagnetic impurities, leading to coherence times exceeding 0.2 s. The combination of nuclear-spin qubits with frequency-multiplexed addressing and lifetime-limited photon emission in the minimal-loss telecommunications C-band establishes 167-Er as a leading platform for long-range, fiber-based quantum networks.

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Alexander Ulanowski, Johannes Früh, Fabian Salamon, Adrian Holzäpfel, Andreas Reiserer. 2026-03-02. Cavity-enhanced optical readout and control of nuclear spin qubits. https://arxiv.org/abs/2603.01987

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