Driven-State Relaxation Of A Coupled Qubit-Defect System In Spin-Locking Measurements

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.