Estimate avoided crossing detuning #1389
Description
To implement a flux-based 2q gate (CZ, iSWAP), an avoided crossing is exploited.
In order to bring the 2q system to the avoided crossing location, the higher-frequency qubit is fluxed in order to reach the crossing location.
The amount of flux required to reach the desired location can be computed intersecting the flux arcs for the desired states. In turn, the flux arcs for the different states can be inferred from the qubit frequencies, anharmonicities, and the flux dependence of the higher-frequency qubit.
Since all the required parameters should be available from previous calibrations, it is not required to perform a large scan to first identify the area (in the flux amplitude-duration plane) of the characteristic Chevron pattern, and the experiment could be automatically focused around the relevant location.
This would help to automate and speed up the 2q gate calibration, since:
- a large Chevron scan would require numerous points, to make sure to capture an unknown location, with a decent feature resolution
- fitting such a large field could be problematic, since the specific pattern is only localized and well-resolved in a limited area
When the decisions are made by a human operator, these problems could be often overcome. But starting from a reasonable estimate would speed up even the manual workflow, which would require only minor adjustments.