Fix global phase tracking for Unroller, OneQubitEulerDecomposer, and ControlledGate #5248
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Summary
Related and (partially) resolves #5235. Fixes some bugs found in handling global phases.
Details and comments
The PR introduces the following changes:
Decomposer
andUnroller
may add twice a global phase if a gate has more than one instructions. See below. This has been fixed.OneQubitEulerDecomposer
. In this way, the global phase in thedefinition
of a 2q-UnitaryGate
is stored. Similar with Fix decomposition in UnitaryGate.definition for 1Q gates #4996 . Previously,_unroll_gate
(L115). This wasn't previously tracked and it was the cause for Incorrect relative phase added for controlled Pauli-X from quantum_info.operators #5235 .