Do not unroll gates in basis in add_control
#13475
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Pull Request Test Coverage Report for Build 11962255098Details
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| if operation.name in basis: | ||
| apply_basic_controlled_gate(controlled_circ, operation, q_control, q_target[0]) | ||
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| # TODO: double check if this is necessary |
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Is this todo completed? if not, how could we check if this is necessary?
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Not yet: I was wondering whether this was necessary because here we don't decompose the gate which we want to control and shouldn't be able to accumulate any global phase. I left it for the first version since the previous code had it, but I'll try removing and see if everything passes 🙂
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| print(self.ugu1) | ||
| print(cgate) |
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sneaky prints!
| print(self.ugu1) | |
| print(cgate) |
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heh classic -- sorry about this one, I think I should add a pre-commit hook to check for these 😂
| @@ -1577,7 +1581,7 @@ def test_single_controlled_rotation_gates(self, gate, cgate): | |||
| elif gate.name == "rz": | |||
| self.assertLessEqual(uqc.size(), 43, f"\n{uqc}") | |||
| else: | |||
| self.assertLessEqual(uqc.size(), 20, f"\n{uqc}") | |||
| self.assertLessEqual(uqc.size(), 23, f"\n{uqc}") | |||
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Why does the size increase in this test? shouldn't the decomposition be more efficient? (I admit I haven't looked in depth so I might be missing something)
Summary
The
add_controlmechanism currently does some redundant unrolling and re-wrapping of gates that are already in the basis of gates we know how to control. This has knock-on effects and causes #13473, by translating an RZ operation (already supported) to a Phase gate.This PR avoids this unrolling. As discussed with @alexanderivrii, in the longer term we should consider rewriting this logic entirely and have a controlled gate plugin, which also allows users to supply their own control mechanism.
Details and comments
U(0,0,0)gates.