Fidelity of remotely entangled nuclear spin states in photon-connected multiqubit registers

The electron spin of a nitrogen-vacancy center in diamond lends itself to the control of proximal $^{13}\mathrm{C}$ nuclear spins via dynamical decoupling methods, possibly combined with radio-frequency driving. Long-lived single-qubit states and high-fidelity electron-nuclear gates required for the realization of a multiqubit register have already been demonstrated. Towards the goal of a scalable architecture, linking multiple such registers in a photonic network represents an important step. Multiple pairs of remotely entangled qubits can enable advanced algorithms or error correction protocols. We investigate how a photonic architecture can be extended from the intrinsic nitrogen spin to multiple $^{13}\mathrm{C}$ spins per node. Applying decoherence-protected gates sequentially, we simulate the fidelity of creating multiple pairs of remotely entangled qubits. Even though the currently achieved degree of control of $^{13}\mathrm{C}$ spins might not be sufficient for large-scale devices, the two schemes are compatible in principle. One requirement is the correction of unconditional phases acquired by unaddressed nuclear spins during a decoupling sequence.