Fix: Initialize.inverse() now raises CircuitError immediately by CosminDinuThiery · Pull Request #15782 · Qiskit/qiskit

CosminDinuThiery · 2026-03-08T16:25:14Z

Summary

Fixes #15595 by raising CircuitError immediately when inverse() is called on a circuit containing Initialize.
Previously, calling inverse() on such circuits would let the computation unfold until crashing with a cryptic and uninformative error.

I have added the tests to cover my changes.
I have updated the documentation accordingly.
I have read the CONTRIBUTING document.

Details and comments

A new inverse() method is added to the Initialize class to override the default inverse() method inherited from the Instruction class.
This fix comes with a test verifying that the correct error is raised, and a release note.

qiskit-bot · 2026-03-08T16:25:19Z

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CLAassistant · 2026-03-08T16:25:20Z

All committers have signed the CLA.

ShellyGarion

Hi @dinuthierycosminpro-debug - thanks for your contribution to qiskit and for fixing this bug.
Could you please handle the Docs and Lint formatting errors?
Other than some more formatting, this PR looks OK to me.

ShellyGarion · 2026-03-09T09:25:12Z

+
+    def inverse(self, annotated: bool = False):
+        """Overrides initialize.inverse() and raise a circuit error"""
+        raise CircuitError ("Initialize is not unitary thus can not be inverted." 


Suggested change

raise CircuitError ("Initialize is not unitary thus can not be inverted."

raise CircuitError ("Initialize is not unitary thus can not be inverted. "

ShellyGarion · 2026-03-09T09:25:31Z

+
+    See `#15595 <https://github.com/Qiskit/qiskit/issues/15595>`__.
+
+


I think that 2 lines of space are not needed.

Co-authored-by: Julien Gacon <gaconju@gmail.com>

Cryoris · 2026-03-09T16:13:01Z

This looks good to me, thanks for the addition @dinuthierycosminpro-debug. We're currently in release freeze for Qiskit v2.4, but once we split the stable branch for that release out we can merge your PR into main. Until then this PR is on hold.

ShellyGarion · 2026-03-09T16:14:12Z

LGTM too, thanks @dinuthierycosminpro-debug for your contribution to qiskit!

CosminDinuThiery · 2026-03-10T08:18:52Z

Thank you for your reviews!

ShellyGarion

Thanks! and your PR is the first to merge in Qiskit 2.5

* Fix: Initialize.inverse() now raises CircuitError immediately * move importations to the beggining * Fix: apply black formatting * Apply suggestions from code review by Cryoris Co-authored-by: Julien Gacon <gaconju@gmail.com> --------- Co-authored-by: Julien Gacon <gaconju@gmail.com> Co-authored-by: Shelly Garion <46566946+ShellyGarion@users.noreply.github.com> (cherry picked from commit 1aeb988)

#15848) * Fix: Initialize.inverse() now raises CircuitError immediately * move importations to the beggining * Fix: apply black formatting * Apply suggestions from code review by Cryoris --------- (cherry picked from commit 1aeb988) Co-authored-by: Cosmin Dinu-Thiery <dinu.thiery.cosmin.pro@gmail.com> Co-authored-by: Julien Gacon <gaconju@gmail.com> Co-authored-by: Shelly Garion <46566946+ShellyGarion@users.noreply.github.com>

CosminDinuThiery requested a review from a team as a code owner March 8, 2026 16:25

qiskit-bot added the Community PR PRs from contributors that are not 'members' of the Qiskit repo label Mar 8, 2026

github-project-automation Bot added this to Contributor Monitoring Mar 8, 2026

CosminDinuThiery added 2 commits March 8, 2026 18:01

Fix: Initialize.inverse() now raises CircuitError immediately

9fd7618

move importations to the beggining

5194046

CosminDinuThiery force-pushed the fix_initialise.inverse()_error branch from 0645cac to 5194046 Compare March 8, 2026 17:01

ShellyGarion self-assigned this Mar 9, 2026

ShellyGarion added the Changelog: Fixed Add a "Fixed" entry in the GitHub Release changelog. label Mar 9, 2026

ShellyGarion added this to the 2.5.0 milestone Mar 9, 2026

ShellyGarion reviewed Mar 9, 2026

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CosminDinuThiery force-pushed the fix_initialise.inverse()_error branch from 0d29b76 to 055a56f Compare March 9, 2026 12:54

Cryoris reviewed Mar 9, 2026

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Comment thread qiskit/circuit/library/data_preparation/initializer.py Outdated

Cryoris reviewed Mar 9, 2026

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Comment thread releasenotes/notes/fix-initialize.inverse()-late-error-1846fbbae82ec011.yaml Outdated

Fix: apply black formatting

9424527

CosminDinuThiery force-pushed the fix_initialise.inverse()_error branch from 055a56f to 9424527 Compare March 9, 2026 13:04

Cryoris reviewed Mar 9, 2026

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Comment thread test/python/circuit/test_initializer.py Outdated

Apply suggestions from code review by Cryoris

0fe1d00

Co-authored-by: Julien Gacon <gaconju@gmail.com>

CosminDinuThiery force-pushed the fix_initialise.inverse()_error branch from 12905b3 to 0fe1d00 Compare March 9, 2026 14:43

Cryoris added the on hold Can not fix yet label Mar 9, 2026

ShellyGarion added this to Qiskit 2.5 Mar 12, 2026

github-project-automation Bot moved this to Ready in Qiskit 2.5 Mar 12, 2026

ShellyGarion moved this from Ready to Done in Qiskit 2.5 Mar 12, 2026

ShellyGarion removed the on hold Can not fix yet label Mar 22, 2026

ShellyGarion approved these changes Mar 22, 2026

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ShellyGarion enabled auto-merge March 22, 2026 09:42

Merge branch 'main' into fix_initialise.inverse()_error

8513e10

ShellyGarion added the stable backport potential Make Mergify open a backport PR to the most recent stable branch on merge. label Mar 22, 2026

ShellyGarion added this pull request to the merge queue Mar 22, 2026

Merged via the queue into Qiskit:main with commit 1aeb988 Mar 22, 2026
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github-project-automation Bot moved this to Done in Contributor Monitoring Mar 22, 2026

mergify Bot mentioned this pull request Mar 22, 2026

Fix: Initialize.inverse() now raises CircuitError immediately (backport #15782) #15848

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Fix: Initialize.inverse() now raises CircuitError immediately#15782

Fix: Initialize.inverse() now raises CircuitError immediately#15782
ShellyGarion merged 5 commits intoQiskit:mainfrom
CosminDinuThiery:fix_initialise.inverse()_error

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	raise CircuitError ("Initialize is not unitary thus can not be inverted."
	raise CircuitError ("Initialize is not unitary thus can not be inverted. "


		See `#15595 <https://github.com/Qiskit/qiskit/issues/15595>`__.

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