def test_compose_method(self, num_qubits):
"""Test compose method"""
samples = 10
num_gates = 10
seed = 600
gates = 'all'
for i in range(samples):
circ1 = random_clifford_circuit(num_qubits,
num_gates,
gates=gates,
seed=seed + i)
circ2 = random_clifford_circuit(num_qubits,
num_gates,
gates=gates,
seed=seed + samples + i)
cliff1 = Clifford(circ1)
cliff2 = Clifford(circ2)
value = cliff1.compose(cliff2)
target = Clifford(circ1.extend(circ2))
self.assertEqual(target, value)
def run(self, dag):
"""Run the OptimizeCliffords pass on `dag`.
Args:
dag (DAGCircuit): the DAG to be optimized.
Returns:
DAGCircuit: the optimized DAG.
"""
blocks = []
prev_node = None
cur_block = []
# Iterate over all nodes and collect consecutive Cliffords over the
# same qubits. In this very first proof-of-concept implementation
# we require the same ordering of qubits, but this restriction will
# be shortly removed. An interesting question is whether we may also
# want to compose Cliffords over different sets of qubits, such as
# cliff1 over qubits [1, 2, 3] and cliff2 over [2, 3, 4].
for node in dag.topological_op_nodes():
if isinstance(node.op, Clifford):
if prev_node is None:
blocks.append(cur_block)
cur_block = [node]
else:
if prev_node.qargs == node.qargs:
cur_block.append(node)
else:
blocks.append(cur_block)
cur_block = [node]
prev_node = node
else:
# not a clifford
if cur_block:
blocks.append(cur_block)
prev_node = None
cur_block = []
if cur_block:
blocks.append(cur_block)
# Replace every discovered block of cliffords by a single clifford
# based on the Cliffords' compose function.
for cur_nodes in blocks:
# Create clifford functions only out of blocks with at least 2 gates
if len(cur_nodes) <= 1:
continue
wire_pos_map = dict(
(qb, ix) for ix, qb in enumerate(cur_nodes[0].qargs))
# Construct a linear circuit
cliff = cur_nodes[0].op
for i, node in enumerate(cur_nodes):
if i > 0:
cliff = Clifford.compose(node.op, cliff, front=True)
# Replace the block by the composed clifford
dag.replace_block_with_op(cur_nodes,
cliff,
wire_pos_map,
cycle_check=False)
return dag
