Qiskit / qiskit / 25496719840

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Commit Message

fix(library): clifford_6_4 template missing global_phase causes silent rejection (#15944)

* fix(library): clifford_6_4 template missing global_phase causes silent rejection

The SHSHSH template has gate unitary e^{i*pi/4}*I but lacked global_phase=-pi/4,
so Operator(clifford_6_4()) was not the identity matrix and TemplateOptimization
silently discarded the template on every run.

Set global_phase = -pi/4 so the full operator is exactly I.

Fixes #14538.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* docs: use RST hyperlinks for issue references in release notes

The :issue: role is not registered in this project's Sphinx config.
Use inline hyperlinks matching the existing convention in releasenotes/.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* fix(library): extend global_phase fix to rzx_xz, rzx_zz1, rzx_zz2, rzx_zz3 templates

The same missing global_phase bug present in clifford_6_4 also affected four
RZX templates. Each had gate content that implemented a non-trivial phase
times I, but lacked the compensating global_phase field, causing
TemplateOptimization to silently reject them.

Corrections:
  - rzx_xz:  global_phase = pi   (gate content e^{i*pi} * I)
  - rzx_zz1: global_phase = pi/2 (gate content e^{-i*pi/2} * I)
  - rzx_zz2: global_phase = pi   (gate content e^{i*pi} * I)
  - rzx_zz3: global_phase = pi   (gate content e^{i*pi} * I)

Also:
  - Strengthen test_templates.py identity check from equiv() to strict ==,
    making it a universal regression guard for all templates.
  - Replace test_template_optimization_accepts_clifford_6_4 with
    test_template_optimization_accepts_all_templates, covering every
    template in the library.
  - Move test_clifford_6_4_is_identity out of test_template_matching.py
    (now covered universally by test_templates.py).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* fix(library): add global_phase to five identity-only-up-to-phase templates

clifford_6_4, rzx_x... (continued)

Coverage Stats

6 of 6 new or added lines in 5 files covered. (100.0%)

3 existing lines in 2 files now uncovered.

106964 of 122062 relevant lines covered (87.63%)

964970.04 hits per line