def _decompose_two_qubit_unitaries(self, op: ops.Operation) -> ops.OP_TREE:
# Known matrix?
if len(op.qubits) == 2:
mat = protocols.unitary(op, None)
if mat is not None:
return two_qubit_decompositions.two_qubit_matrix_to_operations(
op.qubits[0],
op.qubits[1],
mat,
allow_partial_czs=self.allow_partial_czs)
return NotImplemented
def optimization_at(self,
circuit: circuits.Circuit,
index: int,
op: ops.Operation
) -> Optional[circuits.PointOptimizationSummary]:
if len(op.qubits) != 2:
return None
old_operations, indices, matrix = (
self._scan_two_qubit_ops_into_matrix(circuit, index, op.qubits))
old_interaction_count = len([old_op for old_op in old_operations
if len(old_op.qubits) == 2])
switch_to_new = False
switch_to_new |= any(len(old_op.qubits) == 2 and
not (isinstance(old_op, ops.GateOperation) and
isinstance(old_op.gate, ops.CZPowGate))
for old_op in old_operations)
if not self.allow_partial_czs:
switch_to_new |= any(isinstance(old_op, ops.GateOperation) and
isinstance(old_op.gate, ops.CZPowGate)
and old_op.gate.exponent != 1
for old_op in old_operations)
# This point cannot be optimized using this method
if not switch_to_new and old_interaction_count <= 1:
return None
# Find a max-3-cz construction.
new_operations = (
two_qubit_decompositions.two_qubit_matrix_to_operations(
op.qubits[0],
op.qubits[1],
matrix,
self.allow_partial_czs,
self.tolerance,
False))
new_interaction_count = len([new_op for new_op in new_operations
if len(new_op.qubits) == 2])
switch_to_new |= new_interaction_count < old_interaction_count
if not switch_to_new:
return None
return circuits.PointOptimizationSummary(
clear_span=max(indices) + 1 - index,
clear_qubits=op.qubits,
new_operations=new_operations)
def _two_qubit_matrix_to_operations(
self,
q0: 'cirq.Qid',
q1: 'cirq.Qid',
mat: np.ndarray,
) -> Sequence['cirq.Operation']:
"""Decomposes the merged two-qubit gate unitary into the minimum number
of CZ gates.
Args:
q0: The first qubit being operated on.
q1: The other qubit being operated on.
mat: Defines the operation to apply to the pair of qubits.
Returns:
A list of operations implementing the matrix.
"""
return two_qubit_decompositions.two_qubit_matrix_to_operations(
q0, q1, mat, self.allow_partial_czs, self.tolerance, False)
