In Situ Characterization of Qubit Control Lines: A Qubit as a Vector Network Analyzer

In quantum control and quantum computing applications, it is crucial that the control signals reaching the device are free from distortion.
If the system function of the control lines is known, this can be achieved by pre-distorting the controls with its inverse.
We have previously developed a method for in-situ measurement of the system function of the transverse and longitudinal control lines of any qubit in the frequency domain[1], and demonstrated it by characterizing the control lines of a superconducting transmon qubit.

We improve the range and accuracy of our method by including decoherence and removing some of the approximations made.
We also show the effect of pre-distortion on the fidelity of popular non-adiabatic two-qubit operations in superconducting quantum processors.

[1] M. Jerger et al., arXiv:1706.05829