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Flatten controlled-CZ and controlled-CX more consistently #7365

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Merged
merged 3 commits into from
May 23, 2025
+44 −85
Merged

Flatten controlled-CZ and controlled-CX more consistently #7365

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cb4ca25
Flatten controlled-CZ and controlled-CX when possible
daxfohl May 21, 2025
72312a5
Clean up controlled_gate correspondingly
daxfohl May 23, 2025
d70f785
Merge branch 'main' into simplify-controlled-cz
daxfohl May 23, 2025
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88 changes: 24 additions & 64 deletions cirq-core/cirq/ops/common_gates.py
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Original file line number Diff line number Diff line change
Expand Up @@ -222,25 +222,17 @@ def controlled(
A `cirq.ControlledGate` (or `cirq.CXPowGate` if possible) representing
`self` controlled by the given control values and qubits.
"""
if control_values and not isinstance(control_values, cv.AbstractControlValues):
control_values = cv.ProductOfSums(
tuple(
(val,) if isinstance(val, int) else tuple(sorted(val)) for val in control_values
)
)
result = super().controlled(num_controls, control_values, control_qid_shape)
if (
self._global_shift == 0
and isinstance(result, controlled_gate.ControlledGate)
and isinstance(result.control_values, cv.ProductOfSums)
and result.control_values[-1] == (1,)
and result.control_qid_shape[-1] == 2
and result.control_values.is_trivial
):
return cirq.CXPowGate(
exponent=self._exponent, global_shift=self._global_shift
).controlled(
result.num_controls() - 1, result.control_values[:-1], result.control_qid_shape[:-1]
)
if result.control_qid_shape == (2,):
return cirq.CXPowGate(exponent=self._exponent)
if result.control_qid_shape == (2, 2):
return cirq.CCXPowGate(exponent=self._exponent)
return result

def _pauli_expansion_(self) -> value.LinearDict[str]:
Expand Down Expand Up @@ -694,25 +686,17 @@ def controlled(
A `cirq.ControlledGate` (or `cirq.CZPowGate` if possible) representing
`self` controlled by the given control values and qubits.
"""
if control_values and not isinstance(control_values, cv.AbstractControlValues):
control_values = cv.ProductOfSums(
tuple(
(val,) if isinstance(val, int) else tuple(sorted(val)) for val in control_values
)
)
result = super().controlled(num_controls, control_values, control_qid_shape)
if (
self._global_shift == 0
and isinstance(result, controlled_gate.ControlledGate)
and isinstance(result.control_values, cv.ProductOfSums)
and result.control_values[-1] == (1,)
and result.control_qid_shape[-1] == 2
and result.control_values.is_trivial
):
return cirq.CZPowGate(
exponent=self._exponent, global_shift=self._global_shift
).controlled(
result.num_controls() - 1, result.control_values[:-1], result.control_qid_shape[:-1]
)
if result.control_qid_shape == (2,):
return cirq.CZPowGate(exponent=self._exponent)
if result.control_qid_shape == (2, 2):
return cirq.CCZPowGate(exponent=self._exponent)
return result

def _qid_shape_(self) -> tuple[int, ...]:
Expand Down Expand Up @@ -1138,26 +1122,14 @@ def controlled(
A `cirq.ControlledGate` (or `cirq.CCZPowGate` if possible) representing
`self` controlled by the given control values and qubits.
"""
if control_values and not isinstance(control_values, cv.AbstractControlValues):
control_values = cv.ProductOfSums(
tuple(
(val,) if isinstance(val, int) else tuple(sorted(val)) for val in control_values
)
)
result = super().controlled(num_controls, control_values, control_qid_shape)
if (
self._global_shift == 0
and isinstance(result, controlled_gate.ControlledGate)
and isinstance(result.control_values, cv.ProductOfSums)
and result.control_values[-1] == (1,)
and result.control_qid_shape[-1] == 2
):
return cirq.CCZPowGate(
exponent=self._exponent, global_shift=self._global_shift
).controlled(
result.num_controls() - 1, result.control_values[:-1], result.control_qid_shape[:-1]
)
return result
if self._global_shift != 0 or not isinstance(result, controlled_gate.ControlledGate):
return result
return ZPowGate(exponent=self.exponent).controlled(
num_controls=result.num_controls() + 1,
control_values=result.control_values & cv.ProductOfSums([1]),
control_qid_shape=result.control_qid_shape + (2,),
)

def _circuit_diagram_info_(self, args: cirq.CircuitDiagramInfoArgs) -> cirq.CircuitDiagramInfo:
return protocols.CircuitDiagramInfo(
Expand Down Expand Up @@ -1340,26 +1312,14 @@ def controlled(
A `cirq.ControlledGate` (or `cirq.CCXPowGate` if possible) representing
`self` controlled by the given control values and qubits.
"""
if control_values and not isinstance(control_values, cv.AbstractControlValues):
control_values = cv.ProductOfSums(
tuple(
(val,) if isinstance(val, int) else tuple(sorted(val)) for val in control_values
)
)
result = super().controlled(num_controls, control_values, control_qid_shape)
if (
self._global_shift == 0
and isinstance(result, controlled_gate.ControlledGate)
and isinstance(result.control_values, cv.ProductOfSums)
and result.control_values[-1] == (1,)
and result.control_qid_shape[-1] == 2
):
return cirq.CCXPowGate(
exponent=self._exponent, global_shift=self._global_shift
).controlled(
result.num_controls() - 1, result.control_values[:-1], result.control_qid_shape[:-1]
)
return result
if self._global_shift != 0 or not isinstance(result, controlled_gate.ControlledGate):
return result
return XPowGate(exponent=self.exponent).controlled(
num_controls=result.num_controls() + 1,
control_values=result.control_values & cv.ProductOfSums([1]),
control_qid_shape=result.control_qid_shape + (2,),
)

def _qasm_(self, args: cirq.QasmArgs, qubits: tuple[cirq.Qid, ...]) -> str | None:
if self._exponent != 1:
Expand Down
34 changes: 19 additions & 15 deletions cirq-core/cirq/ops/common_gates_test.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -109,19 +109,19 @@ def test_z_init():


@pytest.mark.parametrize(
'input_gate, specialized_output',
'input_gate, specialized_output, base_gate',
[
(cirq.Z, cirq.CZ),
(cirq.CZ, cirq.CCZ),
(cirq.X, cirq.CX),
(cirq.CX, cirq.CCX),
(cirq.ZPowGate(exponent=0.5), cirq.CZPowGate(exponent=0.5)),
(cirq.CZPowGate(exponent=0.5), cirq.CCZPowGate(exponent=0.5)),
(cirq.XPowGate(exponent=0.5), cirq.CXPowGate(exponent=0.5)),
(cirq.CXPowGate(exponent=0.5), cirq.CCXPowGate(exponent=0.5)),
(cirq.Z, cirq.CZ, cirq.Z),
(cirq.CZ, cirq.CCZ, cirq.Z),
(cirq.X, cirq.CX, cirq.X),
(cirq.CX, cirq.CCX, cirq.X),
(cirq.ZPowGate(exponent=0.5), cirq.CZPowGate(exponent=0.5), cirq.S),
(cirq.CZPowGate(exponent=0.5), cirq.CCZPowGate(exponent=0.5), cirq.S),
(cirq.XPowGate(exponent=0.5), cirq.CXPowGate(exponent=0.5), cirq.XPowGate(exponent=0.5)),
(cirq.CXPowGate(exponent=0.5), cirq.CCXPowGate(exponent=0.5), cirq.XPowGate(exponent=0.5)),
],
)
def test_specialized_control(input_gate, specialized_output):
def test_specialized_control(input_gate, specialized_output, base_gate):
# Single qubit control on the input gate gives the specialized output
assert input_gate.controlled() == specialized_output
assert input_gate.controlled(num_controls=1) == specialized_output
Expand Down Expand Up @@ -151,20 +151,24 @@ def test_specialized_control(input_gate, specialized_output):
)

# When a control_value 1 qubit is not acting first, results in a regular
# ControlledGate on the input gate instance.
# ControlledGate on the base gate instance, with any extra control layer
# of the input gate being absorbed into the ControlledGate.
absorbed = 0 if base_gate == input_gate else 1
absorbed_values = ((1,),) * absorbed
absorbed_shape = (2,) * absorbed
assert input_gate.controlled(num_controls=1, control_qid_shape=(3,)) == cirq.ControlledGate(
input_gate, num_controls=1, control_qid_shape=(3,)
base_gate, num_controls=1 + absorbed, control_qid_shape=(3,) + absorbed_shape
)
assert input_gate.controlled(control_values=((0,), (1,), (0,))) == cirq.ControlledGate(
input_gate, num_controls=3, control_values=((0,), (1,), (0,))
base_gate, num_controls=3 + absorbed, control_values=((0,), (1,), (0,)) + absorbed_values
)
assert input_gate.controlled(control_qid_shape=(3, 2, 3)) == cirq.ControlledGate(
input_gate, num_controls=3, control_qid_shape=(3, 2, 3)
base_gate, num_controls=3 + absorbed, control_qid_shape=(3, 2, 3) + absorbed_shape
)
assert input_gate.controlled(control_qid_shape=(3,)).controlled(
control_qid_shape=(2,)
).controlled(control_qid_shape=(4,)) != cirq.ControlledGate(
input_gate, num_controls=3, control_qid_shape=(3, 2, 4)
base_gate, num_controls=3 + absorbed, control_qid_shape=(3, 2, 4) + absorbed_shape
)


Expand Down