def _layout_from_raw(initial_layout, circuit):
if initial_layout is None or isinstance(initial_layout, Layout):
return initial_layout
elif isinstancelist(initial_layout):
if all(isinstanceint(elem) for elem in initial_layout):
initial_layout = Layout.from_intlist(initial_layout, *circuit.qregs)
elif all(elem is None or isinstance(elem, Qubit) for elem in initial_layout):
initial_layout = Layout.from_qubit_list(initial_layout)
elif isinstance(initial_layout, dict):
initial_layout = Layout(initial_layout)
else:
raise TranspilerError("The initial_layout parameter could not be parsed")
return initial_layout
def _compose_non_swap_nodes(self, accumulator: DAGCircuit, layout: Layout,
new_dag: DAGCircuit) -> DAGCircuit:
"""Add all the non-swap strategy nodes that we have accumulated up to now.
This method also resets the node accumulator to an empty dag.
Args:
layout: The current layout that keeps track of the swaps.
new_dag: The new dag that we are building up.
accumulator: A DAG to keep track of nodes that do not decompose
using swap strategies.
Returns:
A new accumulator with the same registers as ``new_dag``.
"""
# Add all the non-swap strategy nodes that we have accumulated up to now.
order = layout.reorder_bits(new_dag.qubits)
order_bits = [None] * len(layout)
for idx, val in enumerate(order):
order_bits[val] = idx
new_dag.compose(accumulator, qubits=order_bits)
# Re-initialize the node accumulator
return new_dag.copy_empty_like()
def test_all_single_qubit(self):
"""Test all trivial layers."""
coupling = CouplingMap([[0, 1], [1, 2], [1, 3]])
qr = QuantumRegister(2, 'q')
ar = QuantumRegister(2, 'a')
cr = ClassicalRegister(4, 'c')
circ = QuantumCircuit(qr, ar, cr)
circ.h(qr)
circ.h(ar)
circ.s(qr)
circ.s(ar)
circ.t(qr)
circ.t(ar)
circ.measure(qr[0], cr[0]) # intentional duplicate
circ.measure(qr[0], cr[0])
circ.measure(qr[1], cr[1])
circ.measure(ar[0], cr[2])
circ.measure(ar[1], cr[3])
dag = circuit_to_dag(circ)
layout = Layout({qr[0]: 0, qr[1]: 1, ar[0]: 2, ar[1]: 3})
pass_ = StochasticSwap(coupling, layout, 20, 13)
after = pass_.run(dag)
self.assertEqual(dag, after)
def test_multiple_registers_with_layout_adjust(self):
"""
Test two registers + measurements using a layout.
The mapper will adjust the initial layout so that
all of the gates can be done without swaps.
"""
coupling = CouplingMap([[0, 1], [1, 2]])
qr_q = QuantumRegister(2, 'q')
qr_a = QuantumRegister(1, 'a')
cr_c = ClassicalRegister(3, 'c')
circ = QuantumCircuit(qr_q, qr_a, cr_c)
circ.cx(qr_q[0], qr_a[0])
circ.cx(qr_q[1], qr_a[0])
circ.measure(qr_q[0], cr_c[0])
circ.measure(qr_q[1], cr_c[1])
circ.measure(qr_a[0], cr_c[2])
dag = circuit_to_dag(circ)
layout = Layout({qr_q[0]: 0, qr_q[1]: 1, qr_a[0]: 2})
pass_ = StochasticSwap(coupling, layout, 20, 13)
after = pass_.run(dag)
self.assertEqual(dag, after)
def test_multi_alap():
qr0 = QuantumRegister(2)
qr1 = QuantumRegister(2)
qc = QuantumCircuit(qr0, qr1)
qc.cx(qr0[0], qr0[1])
qc.cx(qr1[0], qr1[1])
qc.cx(qr1[1], qr1[0])
qc.cx(qr1[0], qr1[1])
qc.measure_all()
layout = Layout({
qr0[0]: 0,
qr0[1]: 1,
qr1[0]: 2,
qr1[1]: 3,
})
durations = InstructionDurations([('cx', None, 1000),
('measure', None, 1000)])
transpiled_qc = transpile(qc, initial_layout=layout)
dag = circuit_to_dag(transpiled_qc)
malap_dag = MultiALAPSchedule(durations).run(dag, time_unit="dt")
print(dag_to_circuit(malap_dag))
assert (malap_dag.duration == 4000)
def test_move_measurements(self):
"""Measurements applied AFTER swap mapping.
"""
backend = FakeRueschlikon()
cmap = backend.configuration().coupling_map
circ = QuantumCircuit.from_qasm_file(
self._get_resource_path('move_measurements.qasm', Path.QASMS))
lay = Layout({
('qa', 0): ('q', 0),
('qa', 1): ('q', 1),
('qb', 0): ('q', 15),
('qb', 1): ('q', 2),
('qb', 2): ('q', 14),
('qN', 0): ('q', 3),
('qN', 1): ('q', 13),
('qN', 2): ('q', 4),
('qc', 0): ('q', 12),
('qNt', 0): ('q', 5),
('qNt', 1): ('q', 11),
('qt', 0): ('q', 6)
})
out = transpile(circ, initial_layout=lay, coupling_map=cmap)
out_dag = circuit_to_dag(out)
meas_nodes = out_dag.named_nodes('measure')
for meas_node in meas_nodes:
is_last_measure = all([
after_measure.type == 'out'
for after_measure in out_dag.quantum_successors(meas_node)
])
self.assertTrue(is_last_measure)
def run(self, dag):
"""
If `dag` is mapped and the direction is correct the property
`is_direction_mapped` is set to True (or to False otherwise).
Args:
dag (DAGCircuit): DAG to check.
"""
if self.layout is None:
if self.property_set["layout"]:
self.layout = self.property_set["layout"]
else:
self.layout = Layout.generate_trivial_layout(
*dag.qregs.values())
self.property_set['is_direction_mapped'] = True
edges = self.coupling_map.get_edges()
for gate in dag.twoQ_gates():
physical_q0 = self.layout[gate.qargs[0]]
physical_q1 = self.layout[gate.qargs[1]]
if isinstance(gate.op,
(CXBase, CnotGate)) and (physical_q0,
physical_q1) not in edges:
self.property_set['is_direction_mapped'] = False
return
def test_already_mapped_1(self):
"""Circuit not remapped if matches topology.
See: https://github.com/Qiskit/qiskit-terra/issues/342
"""
backend = FakeRueschlikon()
coupling_map = backend.configuration().coupling_map
basis_gates = backend.configuration().basis_gates
qr = QuantumRegister(16, 'qr')
cr = ClassicalRegister(16, 'cr')
qc = QuantumCircuit(qr, cr)
qc.cx(qr[3], qr[14])
qc.cx(qr[5], qr[4])
qc.h(qr[9])
qc.cx(qr[9], qr[8])
qc.x(qr[11])
qc.cx(qr[3], qr[4])
qc.cx(qr[12], qr[11])
qc.cx(qr[13], qr[4])
qc.measure(qr, cr)
new_qc = transpile(qc,
coupling_map=coupling_map,
basis_gates=basis_gates,
initial_layout=Layout.generate_trivial_layout(qr))
cx_qubits = [
qargs for (gate, qargs, _) in new_qc.data if gate.name == "cx"
]
cx_qubits_physical = [[ctrl.index, tgt.index]
for [ctrl, tgt] in cx_qubits]
self.assertEqual(sorted(cx_qubits_physical),
[[3, 4], [3, 14], [5, 4], [9, 8], [12, 11], [13, 4]])
def test_3q_circuit_5q_coupling(self):
"""Allocates 2 ancillas for a 3q circuit in a 5q coupling map
0 -> q0
q0 -> 0 1 -> q1
q1 -> 1 => 2 -> q2
q2 -> 2 3 -> ancilla0
4 -> ancilla1
"""
qr = QuantumRegister(3, 'q')
circ = QuantumCircuit(qr)
dag = circuit_to_dag(circ)
initial_layout = Layout()
initial_layout[0] = qr[0]
initial_layout[1] = qr[1]
initial_layout[2] = qr[2]
pass_ = FullAncillaAllocation(self.cmap5)
pass_.property_set['layout'] = initial_layout
pass_.run(dag)
after_layout = pass_.property_set['layout']
ancilla = QuantumRegister(2, 'ancilla')
self.assertEqual(after_layout[0], qr[0])
self.assertEqual(after_layout[1], qr[1])
self.assertEqual(after_layout[2], qr[2])
self.assertEqual(after_layout[3], ancilla[0])
self.assertEqual(after_layout[4], ancilla[1])
def test_3q_with_holes_5q_coupling(self):
"""Allocates 3 ancillas for a 2q circuit on a 5q coupling, with holes
0 -> q0
q0 -> 0 1 -> ancilla0
q1 -> 2 => 2 -> q2
3 -> ancilla1
4 -> ancilla2
"""
qr = QuantumRegister(2, 'q')
circ = QuantumCircuit(qr)
dag = circuit_to_dag(circ)
initial_layout = Layout()
initial_layout[0] = qr[0]
initial_layout[2] = qr[1]
pass_ = FullAncillaAllocation(self.cmap5)
pass_.property_set['layout'] = initial_layout
pass_.run(dag)
after_layout = pass_.property_set['layout']
ancilla = QuantumRegister(3, 'ancilla')
self.assertEqual(after_layout[0], qr[0])
self.assertEqual(after_layout[1], ancilla[0])
self.assertEqual(after_layout[2], qr[1])
self.assertEqual(after_layout[3], ancilla[1])
self.assertEqual(after_layout[4], ancilla[2])
def test_only_output_cx_and_swaps_in_coupling_map(self):
"""Test that output DAG contains only 2q gates from the the coupling map."""
coupling = CouplingMap([[0, 1], [1, 2], [2, 3]])
qr = QuantumRegister(4, 'q')
cr = ClassicalRegister(4, 'c')
circuit = QuantumCircuit(qr, cr)
circuit.h(qr[0])
circuit.cx(qr[0], qr[1])
circuit.cx(qr[0], qr[2])
circuit.cx(qr[0], qr[3])
circuit.measure(qr, cr)
dag = circuit_to_dag(circuit)
layout = Layout({qr[0]: 0, qr[1]: 1, qr[2]: 2, qr[3]: 3})
pass_ = StochasticSwap(coupling, layout, 20, 5)
after = pass_.run(dag)
valid_couplings = [
set([layout[a], layout[b]]) for (a, b) in coupling.get_edges()
]
for _2q_gate in after.twoQ_gates():
self.assertIn(set(_2q_gate.qargs), valid_couplings)
def test_initial_layout_in_different_qregs(self):
""" Using an initial_layout, and with several qregs
0:q1_0:--(+)--
|
1:q0_0:---|---
|
2:q2_0:---.---
CouplingMap map: [0]--[1]--[2]
0:q1_0:--X-------
|
1:q0_0:--X---.---
|
2:q2_0:-----(+)--
"""
coupling = CouplingMap([[0, 1], [1, 2]])
qr0 = QuantumRegister(1, 'q0')
qr1 = QuantumRegister(1, 'q1')
qr2 = QuantumRegister(1, 'q2')
circuit = QuantumCircuit(qr0, qr1, qr2)
circuit.cx(qr1[0], qr2[0])
dag = circuit_to_dag(circuit)
layout = Layout({qr1[0]: 0, qr0[0]: 1, qr2[0]: 2})
expected = QuantumCircuit(qr0, qr1, qr2)
expected.swap(qr1[0], qr0[0])
expected.cx(qr0[0], qr2[0])
pass_ = BasicSwap(coupling, initial_layout=layout)
after = pass_.run(dag)
self.assertEqual(circuit_to_dag(expected), after)
def test_initial_layout(self):
""" Using an initial_layout
0:q1:--(+)--
|
1:q0:---|---
|
2:q2:---.---
CouplingMap map: [0]--[1]--[2]
0:q1:--X-------
|
1:q0:--X---.---
|
2:q2:-----(+)--
"""
coupling = CouplingMap([[0, 1], [1, 2]])
qr = QuantumRegister(3, 'q')
circuit = QuantumCircuit(qr)
circuit.cx(qr[1], qr[2])
dag = circuit_to_dag(circuit)
layout = Layout({qr[1]: 0, qr[0]: 1, qr[2]: 2})
expected = QuantumCircuit(qr)
expected.swap(qr[1], qr[0])
expected.cx(qr[0], qr[2])
pass_ = BasicSwap(coupling, initial_layout=layout)
after = pass_.run(dag)
self.assertEqual(circuit_to_dag(expected), after)
def test_3q_out_of_order_5q_coupling(self):
"""Allocates 2 ancillas a 3q circuit on a 5q coupling map, out of order
0 <- q0
q0 -> 0 1 <- ancilla0
q1 -> 3 => 2 <- q2
q2 -> 2 3 <- q1
4 <- ancilla1
"""
qr = QuantumRegister(3, 'q')
circ = QuantumCircuit(qr)
dag = circuit_to_dag(circ)
initial_layout = Layout()
initial_layout[0] = qr[0]
initial_layout[3] = qr[1]
initial_layout[2] = qr[2]
pass_ = FullAncillaAllocation(self.cmap5)
pass_.property_set['layout'] = initial_layout
pass_.run(dag)
after_layout = pass_.property_set['layout']
ancilla = QuantumRegister(2, 'ancilla')
self.assertEqual(after_layout[0], qr[0])
self.assertEqual(after_layout[1], ancilla[0])
self.assertEqual(after_layout[2], qr[2])
self.assertEqual(after_layout[3], qr[1])
self.assertEqual(after_layout[4], ancilla[1])
def test_with_extension(self):
"""There are 2 virtual qubit to extend."""
ancilla = QuantumRegister(2, 'ancilla')
layout = Layout({0: self.qr3[0], 1: ancilla[0],
2: self.qr3[1], 3: ancilla[1],
4: self.qr3[2]})
layout.add_register(ancilla)
pass_ = EnlargeWithAncilla()
pass_.property_set['layout'] = layout
after = pass_.run(self.dag)
qregs = list(after.qregs.values())
self.assertEqual(2, len(qregs))
self.assertEqual(self.qr3, qregs[0])
self.assertEqual(ancilla, qregs[1])
def test_final_measurement_barrier_for_devices(self, mock_pass):
"""Verify BarrierBeforeFinalMeasurements pass is called in default pipeline for devices."""
circ = QuantumCircuit.from_qasm_file(self._get_resource_path('example.qasm', Path.QASMS))
layout = Layout.generate_trivial_layout(*circ.qregs)
transpile(circ, coupling_map=FakeRueschlikon().configuration().coupling_map,
initial_layout=layout)
self.assertTrue(mock_pass.called)
def create_passmanager(self, coupling_map, initial_layout=None):
"""Returns a PassManager using self.pass_class(coupling_map, initial_layout)"""
passmanager = PassManager()
if initial_layout:
passmanager.append(SetLayout(Layout(initial_layout)))
# pylint: disable=not-callable
passmanager.append(self.pass_class(CouplingMap(coupling_map), **self.additional_args))
return passmanager
def _remap_circuit_faulty_backend(circuit, num_qubits, backend_prop,
faulty_qubits_map):
faulty_qubits = backend_prop.faulty_qubits() if backend_prop else []
disconnected_qubits = {
k
for k, v in faulty_qubits_map.items() if v is None
}.difference(faulty_qubits)
faulty_qubits_map_reverse = {v: k for k, v in faulty_qubits_map.items()}
if faulty_qubits:
faulty_qreg = circuit._create_qreg(len(faulty_qubits), 'faulty')
else:
faulty_qreg = []
if disconnected_qubits:
disconnected_qreg = circuit._create_qreg(len(disconnected_qubits),
'disconnected')
else:
disconnected_qreg = []
new_layout = Layout()
faulty_qubit = 0
disconnected_qubit = 0
for real_qubit in range(num_qubits):
if faulty_qubits_map[real_qubit] is not None:
new_layout[real_qubit] = circuit._layout[
faulty_qubits_map[real_qubit]]
else:
if real_qubit in faulty_qubits:
new_layout[real_qubit] = faulty_qreg[faulty_qubit]
faulty_qubit += 1
else:
new_layout[real_qubit] = disconnected_qreg[disconnected_qubit]
disconnected_qubit += 1
physical_layout_dict = {}
for qubit in circuit.qubits:
physical_layout_dict[qubit] = faulty_qubits_map_reverse[qubit.index]
for qubit in faulty_qreg[:] + disconnected_qreg[:]:
physical_layout_dict[qubit] = new_layout[qubit]
dag_circuit = circuit_to_dag(circuit)
apply_layout_pass = ApplyLayout()
apply_layout_pass.property_set['layout'] = Layout(physical_layout_dict)
circuit = dag_to_circuit(apply_layout_pass.run(dag_circuit))
circuit._layout = new_layout
return circuit
def _remap_layout_faulty_backend(layout, faulty_qubits_map):
if layout is None:
return layout
new_layout = Layout()
for virtual, physical in layout.get_virtual_bits().items():
if faulty_qubits_map[physical] is None:
raise TranspilerError("The initial_layout parameter refers to faulty"
" or disconnected qubits")
new_layout[virtual] = faulty_qubits_map[physical]
return new_layout
def test_full_connected_coupling_map(self):
"""Test if the permutation {0->3,1->0,2->1,3->2} in a fully connected map."""
v = QuantumRegister(4, "v") # virtual qubits
from_layout = Layout({v[0]: 0, v[1]: 1, v[2]: 2, v[3]: 3})
to_layout = Layout({v[0]: 3, v[1]: 0, v[2]: 1, v[3]: 2})
ltpass = LayoutTransformation(coupling_map=None,
from_layout=from_layout,
to_layout=to_layout,
seed=42)
qc = QuantumCircuit(4) # input (empty) physical circuit
dag = circuit_to_dag(qc)
output_dag = ltpass.run(dag)
expected = QuantumCircuit(4)
expected.swap(1, 0)
expected.swap(2, 1)
expected.swap(3, 2)
self.assertEqual(circuit_to_dag(expected), output_dag)
def test_three_qubit(self):
"""Test if the permutation {0->2,1->0,2->1} is implemented correctly."""
v = QuantumRegister(3, "v") # virtual qubits
coupling = CouplingMap([[0, 1], [1, 2]])
from_layout = Layout({v[0]: 0, v[1]: 1, v[2]: 2})
to_layout = Layout({v[0]: 2, v[1]: 0, v[2]: 1})
ltpass = LayoutTransformation(coupling_map=coupling,
from_layout=from_layout,
to_layout=to_layout,
seed=42)
qc = QuantumCircuit(3)
dag = circuit_to_dag(qc)
output_dag = ltpass.run(dag)
expected = QuantumCircuit(3)
expected.swap(1, 0)
expected.swap(1, 2)
self.assertEqual(circuit_to_dag(expected), output_dag)
def test_no_extension(self):
"""There are no virtual qubits to extend."""
layout = Layout({self.qr3[0]: 0, self.qr3[1]: 1, self.qr3[2]: 2})
pass_ = EnlargeWithAncilla(layout)
after = pass_.run(self.dag)
qregs = list(after.qregs.values())
self.assertEqual(1, len(qregs))
self.assertEqual(self.qr3, qregs[0])
def run(self, quantum_circuit):
dag_circuit = circuit_to_dag(quantum_circuit)
init_time = time.time()
self.parameters["TIME_START"] = init_time
initial_mapping = []
if self.parameters["initial_map"] == K7MInitialMapping.RANDOM:
# Only the first positions which correspond to the circuit qubits
initial_mapping = numpy.random.permutation(
self.parameters["nisq_qubits"])
initial_mapping = initial_mapping[:dag_circuit.num_qubits()]
elif self.parameters["initial_map"] == K7MInitialMapping.LINEAR:
initial_mapping = list(range(dag_circuit.num_qubits()))
elif self.parameters["initial_map"] == K7MInitialMapping.HEURISTIC:
initial_mapping = cuthill_order(dag_circuit, self.coupling_obj,
self.parameters)
init_time = time.time() - init_time
if initial_mapping is None:
return None, init_time, None
# print(initial_mapping)
#
# return quantum_circuit
print(" .......")
original_pm = PassManager()
optimal_layout = Layout()
for c_idx, p_idx in enumerate(initial_mapping):
optimal_layout.add(quantum_circuit.qregs[0][c_idx], p_idx)
original_pm.append([
SetLayout(optimal_layout),
ApplyLayout(),
StochasticSwap(self.coupling_obj.coupling, seed=0),
Decompose(gate=qiskit.extensions.SwapGate)
])
return original_pm.run(quantum_circuit), init_time, initial_mapping
def run(self, dag):
"""
Flips the cx nodes to match the directed coupling map.
Args:
dag (DAGCircuit): DAG to map.
Returns:
DAGCircuit: The rearranged dag for the coupling map
Raises:
TranspilerError: If the circuit cannot be mapped just by flipping the
cx nodes.
"""
new_dag = DAGCircuit()
if self.layout is None:
# LegacySwap renames the register in the DAG and does not match the property set
self.layout = Layout.generate_trivial_layout(*dag.qregs.values())
for layer in dag.serial_layers():
subdag = layer['graph']
for cnot_node in subdag.named_nodes('cx', 'CX'):
control = cnot_node.qargs[0]
target = cnot_node.qargs[1]
physical_q0 = self.layout[control]
physical_q1 = self.layout[target]
if self.coupling_map.distance(physical_q0, physical_q1) != 1:
raise TranspilerError(
'The circuit requires a connection between physical '
'qubits %s and %s' % (physical_q0, physical_q1))
if (physical_q0,
physical_q1) not in self.coupling_map.get_edges():
# A flip needs to be done
# Create the involved registers
if control[0] not in subdag.qregs.values():
subdag.add_qreg(control[0])
if target[0] not in subdag.qregs.values():
subdag.add_qreg(target[0])
# Add H gates around
subdag.apply_operation_back(HGate(), [target], [])
subdag.apply_operation_back(HGate(), [control], [])
subdag.apply_operation_front(HGate(), [target], [])
subdag.apply_operation_front(HGate(), [control], [])
# Flips the CX
cnot_node.qargs[0], cnot_node.qargs[1] = target, control
new_dag.extend_back(subdag)
return new_dag
def test_default_pass_manager_two(self):
"""Test default_pass_manager.run(circuitS).
circuit1 and circuit2:
qr0:-[H]--.------------ -> 1
|
qr1:-----(+)--.-------- -> 2
|
qr2:---------(+)--.---- -> 3
|
qr3:-------------(+)--- -> 5
device:
0 - 1 - 2 - 3 - 4 - 5 - 6
| | | | | |
13 - 12 - 11 - 10 - 9 - 8 - 7
"""
qr = QuantumRegister(4, "qr")
circuit1 = QuantumCircuit(qr)
circuit1.h(qr[0])
circuit1.cx(qr[0], qr[1])
circuit1.cx(qr[1], qr[2])
circuit1.cx(qr[2], qr[3])
circuit2 = QuantumCircuit(qr)
circuit2.cx(qr[1], qr[2])
circuit2.cx(qr[0], qr[1])
circuit2.cx(qr[2], qr[3])
coupling_map = FakeMelbourne().configuration().coupling_map
basis_gates = FakeMelbourne().configuration().basis_gates
initial_layout = [None, qr[0], qr[1], qr[2], None, qr[3]]
pass_manager = level_1_pass_manager(
PassManagerConfig(
basis_gates=basis_gates,
coupling_map=CouplingMap(coupling_map),
initial_layout=Layout.from_qubit_list(initial_layout),
seed_transpiler=42,
))
new_circuits = pass_manager.run([circuit1, circuit2])
for new_circuit in new_circuits:
bit_indices = {
bit: idx
for idx, bit in enumerate(new_circuit.qregs[0])
}
for gate, qargs, _ in new_circuit.data:
if isinstance(gate, CXGate):
self.assertIn([bit_indices[x] for x in qargs],
coupling_map)
def test_empty_score(self):
"""Test error rate is 0 for empty circuit."""
bit_map = {}
reverse_bit_map = {}
im_graph = retworkx.PyDiGraph()
backend = FakeYorktownV2()
vf2_pass = VF2PostLayout(target=backend.target)
layout = Layout()
score = vf2_pass._score_layout(layout, bit_map, reverse_bit_map,
im_graph)
self.assertEqual(0, score)
def setUp(self):
coupling = [[0, 1], [1, 2], [2, 3], [3, 4], [4, 5], [5, 6]]
coupling_map = CouplingMap(couplinglist=coupling)
qr = QuantumRegister(7, 'q')
layout = Layout({qr[i]: i for i in range(coupling_map.size())})
self.config = TranspileConfig(optimization_level=1,
basis_gates=['u1', 'u3', 'u2', 'cx'],
initial_layout=layout,
coupling_map=coupling_map,
seed_transpiler=987,
backend_properties=None)
def test_four_qubit(self):
"""Test if the permutation {0->3,1->0,2->1,3->2} is implemented correctly."""
v = QuantumRegister(4, "v") # virtual qubits
coupling = CouplingMap([[0, 1], [1, 2], [2, 3]])
from_layout = Layout({v[0]: 0, v[1]: 1, v[2]: 2, v[3]: 3})
to_layout = Layout({v[0]: 3, v[1]: 0, v[2]: 1, v[3]: 2})
ltpass = LayoutTransformation(coupling_map=coupling,
from_layout=from_layout,
to_layout=to_layout,
seed=42)
qc = QuantumCircuit(4) # input (empty) physical circuit
dag = circuit_to_dag(qc)
output_dag = ltpass.run(dag)
expected = QuantumCircuit(4)
expected.swap(1, 0)
expected.swap(1, 2)
expected.swap(2, 3)
self.assertEqual(circuit_to_dag(expected), output_dag)
def run(self, dag):
"""Run one pass of the lookahead mapper on the provided DAG.
Args:
dag (DAGCircuit): the directed acyclic graph to be mapped
Returns:
DAGCircuit: A dag mapped to be compatible with the coupling_map in
the property_set.
Raises:
TranspilerError: if the coupling map or the layout are not
compatible with the DAG
"""
coupling_map = self._coupling_map
ordered_virtual_gates = list(dag.serial_layers())
if self.initial_layout is None:
if self.property_set["layout"]:
self.initial_layout = self.property_set["layout"]
else:
self.initial_layout = Layout.generate_trivial_layout(
*dag.qregs.values())
if len(dag.qubits()) != len(self.initial_layout):
raise TranspilerError(
'The layout does not match the amount of qubits in the DAG')
if len(self._coupling_map.physical_qubits) != len(self.initial_layout):
raise TranspilerError(
"Mappers require to have the layout to be the same size as the coupling map"
)
mapped_gates = []
layout = self.initial_layout.copy()
gates_remaining = ordered_virtual_gates.copy()
while gates_remaining:
best_step = _search_forward_n_swaps(layout, gates_remaining,
coupling_map)
layout = best_step['layout']
gates_mapped = best_step['gates_mapped']
gates_remaining = best_step['gates_remaining']
mapped_gates.extend(gates_mapped)
# Preserve input DAG's name, regs, wire_map, etc. but replace the graph.
mapped_dag = _copy_circuit_metadata(dag, coupling_map)
for node in mapped_gates:
mapped_dag.apply_operation_back(op=node.op,
qargs=node.qargs,
cargs=node.cargs)
return mapped_dag
def test_three_qubit(self):
"""Test if the permutation {0->2,1->0,2->1} is implemented correctly."""
np.random.seed(0)
v = QuantumRegister(3, 'v') # virtual qubits
coupling = CouplingMap([[0, 1], [1, 2]])
from_layout = Layout({v[0]: 0, v[1]: 1, v[2]: 2})
to_layout = Layout({v[0]: 2, v[1]: 0, v[2]: 1})
ltpass = LayoutTransformation(coupling_map=coupling,
from_layout=from_layout,
to_layout=to_layout)
qc = QuantumCircuit(3) # input (empty) physical circuit
dag = circuit_to_dag(qc)
q = dag.qubits()
output_dag = ltpass.run(dag)
# output_dag.draw()
# Check that only two swaps were performed
self.assertCountEqual(["swap"] * 2, [op.name for op in output_dag.topological_op_nodes()])
# And check that the swaps were first performed on {q0,q1} then on {q1,q2}.
self.assertEqual([frozenset([q[0], q[1]]), frozenset([q[1], q[2]])],
[frozenset(op.qargs) for op in output_dag.topological_op_nodes()])
