fix-1q-matrix-bug-in-quantum-shannon-decomposer-c99ce6509f03715b.yaml

---
fixes:
  - |
    When :func:`~qiskit.quantum_info.synthesis.qs_decomposition`, which does quantum Shannon
    decomposition, was called on trivial numeric unitaries that do not benefit from this
    decomposition, an unexpected error was raised. With this fix, such unitaries are detected and
    the equivalent circuit is returned without performing Shannon decomposition.