Mthree

What's new

- Mappings returned by `mthree.utils.final_measurement_mapping` now have keys that represent the classical bits, and values that indicate the qubit that was measured into that bit. **This is a breaking change for those who create their own mappings**. This takes care of mid-circuit measurements automatically.

- Setting `method='independent'` for simulators is now done internally for the user by default. It is possible to override defaults by setting this keyword argument explicitly.

- Docs expanded a bit with examples for sampling problems looking at the most probable bit-string, and correcting mid-circuit measurements.

Bug fixes

- M3 is now compatible with Qiskit's fake backends that use `BackendV2` as their base class.
- Fixed an issue where calibration data could not be saved when performing calibrations in async mode.


Thanks to mtreinish and ehchen for their help in this release.

Fixes
Allows for `delay` instructions at the end of a circuit and still record measurements as "final": https://github.com/Qiskit/qiskit-ibm-runtime/issues/481


Notes

The above fix is related to a much larger effort needed to correct mid-circuit measurements when the results are deferred to the end.

This release requires `qiskit-terra >= 0.21` and the corresponding IBM Quantum provider (`>=0.19.2`)

New

- Doing the correct calculation for the balanced calibration method is now done internally. This ensures that users get the correct precision for the measurement error rates for all methods (119)

- Allow for easily correcting low-weight operators via utility functions that compute marginal distributions and the correct mappings (120 ).

New

- Does balanced calibration math internally. This means that the precision set by the number of shots used for calibration is the same for all calibration methods. This also means the overhead from balanced calibration does not depend on the number of qubits (assuming the overhead is linear in the number of shots and independent of the number of circuits executed).

- Added a documentation section that briefly explains the balanced calibrations.

- Setting openmp can be done via `--openmp` now as well as the old way `--with-openmp`. The latter will be dropped at some point in the future.

Changes

- Calibration save times are now in UTC rather than local time
- Add Py310 support
- Dropped support for Py36
- Wheels build now use manylinux 2014
- Remove use of deprecated Qiskit `BaseBackend`
- Bypass transpiler when generating calibration circuits

Fixes

- Fixed a bug in deployment (96).