Each backend has a version number in the form X.X.X (major.minor.revision) where X is an integer. A circuit compiled for a given backend version number is guaranteed to run on that backend. If the revision number changes, the circuit will continue to run. If the major or minor number changes, the circuit is not guaranteed to run, although it may do so. The conditions under which a version number may change are listed below:
The major version will increment for system changes such as:
Major changes to the control electronics.
Moving the system to a new location, if significant behavior changes result.
The minor version will increment for changes such as:
Warmup / cool-down cycles.
Swapping out some electronics, if the replacement appreciably affects operation.
Changing the direction of a controlled-NOT gate.
Dropping a gate for some duration of time due to calibration issues, and corrections cannot readily be done in software.
The revision version number will increment for fixes that do not break the existing compiled circuit. These changes include:
Manual calibrations to improve fidelities.
Small electronics changes that don’t affect operation.
Backend software updates.