  Certain quantum sensing protocols rely on qubits that are initialized,
coherently driven in the presence of a stimulus to be measured, then read out.
Most widely employed pulse sequences used to drive sensing qubits act locally
in either the time or frequency domain. We introduce a generalized set of
sequences that effect a measurement in any fractional Fourier domain, i.e.
along a linear trajectory of arbitrary angle through the time-frequency plane.
Using an ensemble of nitrogen-vacancy centers we experimentally demonstrate
advantages in sensing signals with time-varying spectra.
