Spins associated to optically accessible solid-state defects have emerged as
a versatile platform for exploring quantum simulation, quantum sensing and
quantum communication. Pioneering experiments have shown the sensing, imaging,
and control of multiple nuclear spins surrounding a single electron-spin
defect. However, the accessible size and complexity of these spin networks has
been constrained by the spectral resolution of current methods. Here, we map a
network of 50 coupled spins through high-resolution correlated sensing schemes,
using a single nitrogen-vacancy center in diamond. We develop concatenated
double-resonance sequences that identify spin-chains through the network. These
chains reveal the characteristic spin frequencies and their interconnections
with high spectral resolution, and can be fused together to map out the
network. Our results provide new opportunities for quantum simulations by
increasing the number of available spin qubits. Additionally, our methods might
find applications in nano-scale imaging of complex spin systems external to the
host crystal.Comment: 7 pages, 5 figure