def test_cnot_rxx_decompose(self):
"""Verify CNOT decomposition into RXX gate is correct"""
cnot = Operator(CXGate())
decomps = [cnot_rxx_decompose(),
cnot_rxx_decompose(plus_ry=True, plus_rxx=True),
cnot_rxx_decompose(plus_ry=True, plus_rxx=False),
cnot_rxx_decompose(plus_ry=False, plus_rxx=True),
cnot_rxx_decompose(plus_ry=False, plus_rxx=False)]
for decomp in decomps:
self.assertTrue(cnot.equiv(decomp))
def run(self, dag):
"""Run the MSBasisDecomposer pass on `dag`.
Replace U3,CX nodes in input dag with equivalent Rx,Ry,Rxx gates.
Args:
dag(DAGCircuit): input dag
Raises:
QiskitError: if input dag includes gates outside U3,CX.
Returns:
DAGCircuit: output dag
"""
one_q_decomposer = OneQubitEulerDecomposer(basis="XYX")
cnot_decomposition = cnot_rxx_decompose()
for node in dag.op_nodes():
basic_insts = ["measure", "reset", "barrier", "snapshot", "delay"]
if node.name in basic_insts:
# TODO: this is legacy behavior. basic_insts should be removed and these
# instructions should be part of the device-reported basis. Currently, no
# backend reports "measure", for example.
continue
if node.name in self.basis_gates: # If already a base, ignore.
continue
if not isinstance(node.op, self.supported_input_gates):
raise QiskitError(
"Cannot convert the circuit to the given basis, %s. "
"No rule to expand instruction %s." % (str(self.basis_gates), node.op.name)
)
if isinstance(node.op, U3Gate):
replacement_circuit = one_q_decomposer(node.op)
elif isinstance(node.op, CXGate):
# N.B. We can't circuit_to_dag once outside the loop because
# substitute_node_with_dag will modify the input DAG if the
# node to be replaced is conditional.
replacement_circuit = cnot_decomposition
else:
raise QiskitError(
f"Unable to handle instruction ({node.op.name}, {type(node.op)})."
)
replacement_dag = circuit_to_dag(replacement_circuit)
# N.B. wires kwarg can be omitted for both 1Q and 2Q substitutions.
# For 1Q, one-to-one mapping is always correct. For 2Q,
# cnot_rxx_decompose follows convention of control as q[0], target
# as q[1], which matches qarg order in CX node.
dag.substitute_node_with_dag(node, replacement_dag)
return dag
def_x = QuantumCircuit(q)
for inst, qargs, cargs in [
(HGate(), [q[0]], []),
(SGate(), [q[0]], []),
(SGate(), [q[0]], []),
(HGate(), [q[0]], []),
]:
def_x.append(inst, qargs, cargs)
_sel.add_equivalence(XGate(), def_x)
# CXGate
for plus_ry in [False, True]:
for plus_rxx in [False, True]:
cx_to_rxx = cnot_rxx_decompose(plus_ry, plus_rxx)
_sel.add_equivalence(CXGate(), cx_to_rxx)
q = QuantumRegister(2, "q")
cx_to_cz = QuantumCircuit(q)
for inst, qargs, cargs in [
(HGate(), [q[1]], []),
(CZGate(), [q[0], q[1]], []),
(HGate(), [q[1]], []),
]:
cx_to_cz.append(inst, qargs, cargs)
_sel.add_equivalence(CXGate(), cx_to_cz)
q = QuantumRegister(2, "q")
cx_to_iswap = QuantumCircuit(q, global_phase=3 * pi / 4)
for inst, qargs, cargs in [
