  It is widely known that spin-locking noise-spectroscopy is a powerful
technique for the characterization of low-frequency noise mechanisms in
superconducting qubits. Here we show that the relaxation rate of the driven
spin-locking state of a qubit can be significantly affected by the presence of
an off-resonant high-frequency two-level-system defect. Thus, both low- and
high-frequency defects should be taken into account in the interpretation of
spin-locking measurements and other types of driven-state noise-spectroscopy.
