  Quantum adiabatic passages can be greatly accelerated by a suitable control
field, called a counter-diabatic field, which varies during the scan through
resonance. Here, we implement this technique on the electron spin of a single
nitrogen-vacancy center in diamond. We demonstrate two versions of this scheme.
The first follows closely the procedure originally proposed by Demirplak and
Rice (J. Phys. Chem. A 107, 9937 (2003)). In the second scheme, we use a
control field whose amplitude is constant, but its phase varies with time. This
version, which we call the rapid-scan approach, allows an even faster passage
through resonance and therefore makes it applicable also for systems with
shorter decoherence times.
