def decompose(self):
"""Call a decomposition pass on this circuit,
to decompose one level (shallow decompose).
Returns:
QuantumCircuit: a circuit one level decomposed
"""
from qiskit.transpiler.passes.decompose import Decompose
from qiskit.converters.circuit_to_dag import circuit_to_dag
from qiskit.converters.dag_to_circuit import dag_to_circuit
pass_ = Decompose()
decomposed_dag = pass_.run(circuit_to_dag(self))
return dag_to_circuit(decomposed_dag)
def default_pass_manager(basis_gates, coupling_map, initial_layout,
seed_transpiler):
"""
The default pass manager that maps to the coupling map.
Args:
basis_gates (list[str]): list of basis gate names supported by the target.
coupling_map (CouplingMap): coupling map to target in mapping.
initial_layout (Layout or None): initial layout of virtual qubits on physical qubits
seed_transpiler (int or None): random seed for stochastic passes.
Returns:
PassManager: A pass manager to map and optimize.
"""
pass_manager = PassManager()
pass_manager.property_set['layout'] = initial_layout
pass_manager.append(Unroller(basis_gates))
# Use the trivial layout if no layout is found
pass_manager.append(
TrivialLayout(coupling_map),
condition=lambda property_set: not property_set['layout'])
# if the circuit and layout already satisfy the coupling_constraints, use that layout
# otherwise layout on the most densely connected physical qubit subset
pass_manager.append(CheckMap(coupling_map))
pass_manager.append(
DenseLayout(coupling_map),
condition=lambda property_set: not property_set['is_swap_mapped'])
# Extend the the dag/layout with ancillas using the full coupling map
pass_manager.append(FullAncillaAllocation(coupling_map))
pass_manager.append(EnlargeWithAncilla())
# Circuit must only contain 1- or 2-qubit interactions for swapper to work
pass_manager.append(Unroll3qOrMore())
# Swap mapper
pass_manager.append(
LegacySwap(coupling_map, trials=20, seed=seed_transpiler))
# Expand swaps
pass_manager.append(Decompose(SwapGate))
# Change CX directions
pass_manager.append(CXDirection(coupling_map))
# Unroll to the basis
pass_manager.append(Unroller(['u1', 'u2', 'u3', 'id', 'cx']))
# Simplify single qubit gates and CXs
simplification_passes = [
Optimize1qGates(),
CXCancellation(),
RemoveResetInZeroState()
]
pass_manager.append(
simplification_passes + [Depth(), FixedPoint('depth')],
do_while=lambda property_set: not property_set['depth_fixed_point'])
return pass_manager
