  In a solid-state spin system, we experimentally demonstrate a protocol for
quantum-state population transfer with an improved efficiency compared to
traditional stimulated Raman adiabatic passage (STIRAP). Using the ground-state
triplet of the nitrogen-vacancy center in diamond, we show that the required
evolution time for high-fidelity state transfer can be reduced by almost one
order of magnitude. Furthermore, we establish an improved robustness against
frequency detuning caused by magnetic noise as compared to STIRAP. These
results provide a powerful tool for coherent spin manipulation in the context
of quantum sensing and quantum computation.
