  The individual and coherent control of solid-state based electron spins is
important covering fields from quantum information processing and quantum
metrology to material research and medical imaging. Especially for the control
of individual spins in nanoscale networks, the generation of strong, fast and
localized magnetic fields is crucial. Highly-engineered devices that
demonstrate most of the desired features are found in nanometer size magnetic
writers of hard disk drives (HDD). Currently, however, their nanoscale
operation, in particular, comes at the cost of excessive magnetic noise. Here,
we present HDD writers as a tool for the efficient manipulation of single as
well as multiple spins. We show that their tunable gradients of up to 100
{\mu}T/nm can be used to spectrally address individual spins on the nanoscale.
Their GHz Bandwidth allows to switch control fields within nanoseconds, faster
than characteristic timescales such as Rabi and Larmor periods, spin-spin
couplings or optical transitions, thus extending the set of feasible spin
manipulations. We used the fields to drive spin transitions through
non-adiabatic fast passages or enable the optical readout of spin states in
strong misaligned fields. Building on these techniques, we further apply the
large magnetic field gradients for microwave selective addressing of single
spins and show its use for the nanoscale optical colocalization of two
emitters.
