  To exploit the sub-nanometre dimensions of qubits for large-scale quantum
information processing, corresponding control architectures require both energy
and space efficiency, with the on-chip footprint of unit-cell electronics
ideally micron-scale. However, the spin coherence of qubits in close packing is
severely deteriorated by microwave crosstalk from neighbouring control sites.
Here, we present a crosstalk-mitigation scheme using foundry microelectronics,
to address solid-state spins at sub-100 um spacing without the need for
qubit-detuning. Using nitrogen-vacancy centres in nanodiamonds as qubit
prototypes, we first demonstrate 10 MHz Rabi oscillation at milliwatts of
microwave power. Implementing the active cancellation, we then prove that the
crosstalk field from neighbouring lattice sites can be reduced to undetectable
levels. We finally extend the scheme to show increased qubit control, tripling
the spin coherence under crosstalk mitigation. Compatible with integrated
optics, our results present a step towards scalable control across quantum
platforms using silicon microelectronics.
