Cavity-enhanced optical readout and control of nuclear spin qubits.

Embedding 167 Er dopants in yttrium orthosilicate within a cavity achieves 91% single-shot optical readout fidelity of nuclear spin qubits.

• Why it matters: Nuclear spins in solids are promising for quantum memories due to their long coherence times, but all-optical control and readout have been challenging, limiting their practical use in quantum networks.
• What they did: Researchers used a cryogenic Fabry-Perot cavity with a linewidth of 65 MHz to enhance frequency-selective emission from 167 Er dopants, enabling precise optical readout and control of nuclear spin states.
• The result: This approach yields coherence times over 0.2 seconds and lifetime-limited photon emission in the telecommunications C-band, positioning 167 Er as a key platform for fiber-based quantum communication.