High-Fidelity Single-Shot Readout and Selective Nuclear Spin Control for a Spin-1/2 Quantum Register in Diamond

Quantum networks aim to overcome scalability challenges of single quantum devices by connecting multiple nodes into scalable architectures. Group-IV color centers with their efficient spin-photon interfaces paired with long-lived nuclear spins in diamond have emerged as promising candidates in this context, demonstrating entanglement distribution over metropolitan distances and proof-of-concept blind quantum computing. However, their spin-1/2 nature makes the identification and control of nearby nuclear spins challenging, limiting progress toward scalable multi-qubit nodes and fault-tolerant operation.

Here, we present the germanium-vacancy (GeV) center in diamond as a viable platform for such network nodes. By advancing the correlation spectroscopy method, we precisely identify individual nuclear spins within a convoluted spin environment, enabling their indirect control. We further demonstrate high single-shot readout fidelities of 95.8% for the GeV and 93% for a nearby ¹³C nucleus, achieved through optimized readout schemes. The demonstrated fidelities approach the threshold required for feed-forward error correction, and the methods for spectroscopy and control are directly transferable to other solid-state spin-1/2 platforms. Together, these results establish the GeV center as a promising platform for next-generation quantum network nodes.