"cx": CXGate(),

"cz": CZGate(),

"iswap": iSwapGate(),

"rxx": RXXGate(pi / 2),

"ecr": ECRGate(),

"rzx": RZXGate(pi / 4), # typically pi/6 is also available

"""Choose the first available 2q gate to use in the KAK decomposition."""

kak_gate = None

kak_gates = set(basis_gates or []).intersection(KAK_GATE_NAMES.keys())

if kak_gates:

kak_gate = KAK_GATE_NAMES[kak_gates.pop()]

"""Choose the first available 1q basis to use in the Euler decomposition."""

basis_set = set(basis_gates or [])

decomposers = _possible_decomposers(basis_set)

if decomposers:

return decomposers[0]

"""Find the matching basis string keys from the list of basis gates from the backend."""

if basis_gates is None:

basis_set = set()

else:

basis_set = set(basis_gates)

if basis_dict is None:

basis_dict = one_qubit_decompose.ONE_QUBIT_EULER_BASIS_GATES

out_basis = []

for basis, gates in basis_dict.items():

if set(gates).issubset(basis_set):

out_basis.append(basis)

decomposer2q = None

kak_gate = _choose_kak_gate(basis_gates)

euler_basis = _choose_euler_basis(basis_gates)

basis_fidelity = approximation_degree or 1.0

if isinstance(kak_gate, RZXGate):

backup_optimizer = TwoQubitBasisDecomposer(

CXGate(),

basis_fidelity=basis_fidelity,

euler_basis=euler_basis,

pulse_optimize=pulse_optimize,

)

decomposer2q = XXDecomposer(euler_basis=euler_basis, backup_optimizer=backup_optimizer)

elif kak_gate is not None:

decomposer2q = TwoQubitBasisDecomposer(

kak_gate,

basis_fidelity=basis_fidelity,

euler_basis=euler_basis,

pulse_optimize=pulse_optimize,

)

"""

Calculate a rough error for a `circuit` that runs on specific

`qubits` of `target`.

Use basis errors from target if available, otherwise use length

of circuit as a weak proxy for error.

"""

if target is None:

if isinstance(circuit, DAGCircuit):

return len(circuit.op_nodes())

else:

return len(circuit)

gate_fidelities = []

gate_durations = []

def score_instruction(inst, inst_qubits):

try:

keys = target.operation_names_for_qargs(inst_qubits)

for key in keys:

target_op = target.operation_from_name(key)

if isinstance(circuit, DAGCircuit):

op = inst.op

else:

op = inst.operation

if isinstance(target_op, op.base_class) and (

target_op.is_parameterized()

or all(

isclose(float(p1), float(p2)) for p1, p2 in zip(target_op.params, op.params)

)

):

inst_props = target[key].get(inst_qubits, None)

if inst_props is not None:

error = getattr(inst_props, "error", 0.0) or 0.0

duration = getattr(inst_props, "duration", 0.0) or 0.0

gate_fidelities.append(1 - error)

gate_durations.append(duration)

else:

gate_fidelities.append(1.0)

gate_durations.append(0.0)

break

else:

raise KeyError

except KeyError as error:

if isinstance(circuit, DAGCircuit):

op = inst.op

else:

op = inst.operation

raise TranspilerError(

f"Encountered a bad synthesis. " f"Target has no {op} on qubits {qubits}."

) from error

if isinstance(circuit, DAGCircuit):

for inst in circuit.topological_op_nodes():

inst_qubits = tuple(qubits[circuit.find_bit(q).index] for q in inst.qargs)

score_instruction(inst, inst_qubits)

else:

for inst in circuit:

inst_qubits = tuple(qubits[circuit.find_bit(q).index] for q in inst.qubits)

score_instruction(inst, inst_qubits)

# TODO:return np.sum(gate_durations)

decomposer2q, qubits, natural_direction, coupling_map=None, gate_lengths=None, gate_errors=None

):

"""

`decomposer2q` decomposes an SU(4) over `qubits`. A user sets `natural_direction`

to indicate whether they prefer synthesis in a hardware-native direction.

If yes, we return the `preferred_direction` here. If no hardware direction is

preferred, we raise an error (unless natural_direction is None).

We infer this from `coupling_map`, `gate_lengths`, `gate_errors`.

Returns [0, 1] if qubits are correct in the hardware-native direction.

Returns [1, 0] if qubits must be flipped to match hardware-native direction.

"""

qubits_tuple = tuple(qubits)

reverse_tuple = qubits_tuple[::-1]

preferred_direction = None

if natural_direction in {None, True}:

# find native gate directions from a (non-bidirectional) coupling map

if coupling_map is not None:

neighbors0 = coupling_map.neighbors(qubits[0])

zero_one = qubits[1] in neighbors0

neighbors1 = coupling_map.neighbors(qubits[1])

one_zero = qubits[0] in neighbors1

if zero_one and not one_zero:

preferred_direction = [0, 1]

if one_zero and not zero_one:

preferred_direction = [1, 0]

# otherwise infer natural directions from gate durations or gate errors

if preferred_direction is None and (gate_lengths or gate_errors):

cost_0_1 = inf

cost_1_0 = inf

try:

cost_0_1 = next(

duration

for gate, duration in gate_lengths.get(qubits_tuple, [])

if gate == decomposer2q.gate

)

except StopIteration:

pass

try:

cost_1_0 = next(

duration

for gate, duration in gate_lengths.get(reverse_tuple, [])

if gate == decomposer2q.gate

)

except StopIteration:

pass

if not (cost_0_1 < inf or cost_1_0 < inf):

try:

cost_0_1 = next(

error

for gate, error in gate_errors.get(qubits_tuple, [])

if gate == decomposer2q.gate

)

except StopIteration:

pass

try:

cost_1_0 = next(

error

for gate, error in gate_errors.get(reverse_tuple, [])

if gate == decomposer2q.gate

)

except StopIteration:

pass

if cost_0_1 < cost_1_0:

preferred_direction = [0, 1]

elif cost_1_0 < cost_0_1:

preferred_direction = [1, 0]

if natural_direction is True and preferred_direction is None:

raise TranspilerError(

f"No preferred direction of gate on qubits {qubits} "

"could be determined from coupling map or "

"gate lengths / gate errors."

)

"""Synthesize gates according to their basis gates."""

def __init__(

self,

basis_gates: list[str] = None,

approximation_degree: float | None = 1.0,

coupling_map: CouplingMap = None,

backend_props: BackendProperties = None,

pulse_optimize: bool | None = None,

natural_direction: bool | None = None,

synth_gates: list[str] | None = None,

method: str = "default",

min_qubits: int = None,

plugin_config: dict = None,

target: Target = None,

):

"""Synthesize unitaries over some basis gates.

This pass can approximate 2-qubit unitaries given some

gate fidelities (either via ``backend_props`` or ``target``).

More approximation can be forced by setting a heuristic dial

``approximation_degree``.

Args:

basis_gates (list[str]): List of gate names to target. If this is

not specified the ``target`` argument must be used. If both this

and the ``target`` are specified the value of ``target`` will

be used and this will be ignored.

approximation_degree (float): heuristic dial used for circuit approximation

(1.0=no approximation, 0.0=maximal approximation). Approximation can

make the synthesized circuit cheaper at the cost of straying from

the original unitary. If None, approximation is done based on gate fidelities.

coupling_map (CouplingMap): the coupling map of the backend

in case synthesis is done on a physical circuit. The

directionality of the coupling_map will be taken into

account if ``pulse_optimize`` is ``True``/``None`` and ``natural_direction``

is ``True``/``None``.

backend_props (BackendProperties): Properties of a backend to

synthesize for (e.g. gate fidelities).

pulse_optimize (bool): Whether to optimize pulses during

synthesis. A value of ``None`` will attempt it but fall

back if it does not succeed. A value of ``True`` will raise

an error if pulse-optimized synthesis does not succeed.

natural_direction (bool): Whether to apply synthesis considering

directionality of 2-qubit gates. Only applies when

``pulse_optimize`` is ``True`` or ``None``. The natural direction is

determined by first checking to see whether the

coupling map is unidirectional. If there is no

coupling map or the coupling map is bidirectional,

the gate direction with the shorter

duration from the backend properties will be used. If

set to True, and a natural direction can not be

determined, raises :class:`.TranspilerError`. If set to None, no

exception will be raised if a natural direction can

not be determined.

synth_gates (list[str]): List of gates to synthesize. If None and

``pulse_optimize`` is False or None, default to

``['unitary']``. If ``None`` and ``pulse_optimize == True``,

default to ``['unitary', 'swap']``

method (str): The unitary synthesis method plugin to use.

min_qubits: The minimum number of qubits in the unitary to synthesize. If this is set

and the unitary is less than the specified number of qubits it will not be

synthesized.

plugin_config: Optional extra configuration arguments (as a ``dict``)

which are passed directly to the specified unitary synthesis

plugin. By default, this will have no effect as the default

plugin has no extra arguments. Refer to the documentation of

your unitary synthesis plugin on how to use this.

target: The optional :class:`~.Target` for the target device the pass

is compiling for. If specified this will supersede the values

set for ``basis_gates``, ``coupling_map``, and ``backend_props``.

Raises:

TranspilerError: if ``method`` was specified but is not found in the

installed plugins list. The list of installed plugins can be queried with

:func:`~qiskit.transpiler.passes.synthesis.plugin.unitary_synthesis_plugin_names`

"""

super().__init__()

self._basis_gates = set(basis_gates or ())

self._approximation_degree = approximation_degree

self._min_qubits = min_qubits

self.method = method

self.plugins = None

if method != "default":

self.plugins = plugin.UnitarySynthesisPluginManager()

self._coupling_map = coupling_map

self._backend_props = backend_props

self._pulse_optimize = pulse_optimize

self._natural_direction = natural_direction

self._plugin_config = plugin_config

self._target = target

if target is not None:

self._coupling_map = self._target.build_coupling_map()

if synth_gates:

self._synth_gates = synth_gates

else:

if pulse_optimize:

self._synth_gates = ["unitary", "swap"]

else:

self._synth_gates = ["unitary"]

self._synth_gates = set(self._synth_gates) - self._basis_gates

if self.method != "default" and self.method not in self.plugins.ext_plugins:

raise TranspilerError(f"Specified method '{self.method}' not found in plugin list")

def run(self, dag: DAGCircuit) -> DAGCircuit:

"""Run the UnitarySynthesis pass on ``dag``.

Args:

dag: input dag.

Returns:

Output dag with UnitaryGates synthesized to target basis.

"""

# If there aren't any gates to synthesize in the circuit we can skip all the iteration

# and just return.

if not set(self._synth_gates).intersection(dag.count_ops()):

return dag

if self.plugins:

plugin_method = self.plugins.ext_plugins[self.method].obj

else:

plugin_method = DefaultUnitarySynthesis()

plugin_kwargs: dict[str, Any] = {"config": self._plugin_config}

_gate_lengths = _gate_errors = None

_gate_lengths_by_qubit = _gate_errors_by_qubit = None

if self.method == "default":

# If the method is the default, we only need to evaluate one set of keyword arguments.

# To simplify later logic, and avoid cases where static analysis might complain that we

# haven't initialised the "default" handler, we rebind the names so they point to the

# same object as the chosen method.

default_method = plugin_method

default_kwargs = plugin_kwargs

method_list = [(plugin_method, plugin_kwargs)]

else:

# If the method is not the default, we still need to initialise the default plugin's

# keyword arguments in case we have to fall back on it during the actual run.

default_method = self.plugins.ext_plugins["default"].obj

default_kwargs = {}

method_list = [(plugin_method, plugin_kwargs), (default_method, default_kwargs)]

for method, kwargs in method_list:

if method.supports_basis_gates:

kwargs["basis_gates"] = self._basis_gates

if method.supports_natural_direction:

kwargs["natural_direction"] = self._natural_direction

if method.supports_pulse_optimize:

kwargs["pulse_optimize"] = self._pulse_optimize

if method.supports_gate_lengths:

_gate_lengths = _gate_lengths or _build_gate_lengths(

self._backend_props, self._target

)

kwargs["gate_lengths"] = _gate_lengths

if method.supports_gate_errors:

_gate_errors = _gate_errors or _build_gate_errors(self._backend_props, self._target)

kwargs["gate_errors"] = _gate_errors

if method.supports_gate_lengths_by_qubit:

_gate_lengths_by_qubit = _gate_lengths_by_qubit or _build_gate_lengths_by_qubit(

self._backend_props, self._target

)

kwargs["gate_lengths_by_qubit"] = _gate_lengths_by_qubit

if method.supports_gate_errors_by_qubit:

_gate_errors_by_qubit = _gate_errors_by_qubit or _build_gate_errors_by_qubit(

self._backend_props, self._target

)

kwargs["gate_errors_by_qubit"] = _gate_errors_by_qubit

supported_bases = method.supported_bases

if supported_bases is not None:

kwargs["matched_basis"] = _choose_bases(self._basis_gates, supported_bases)

if method.supports_target:

kwargs["target"] = self._target

# Handle approximation degree as a special case for backwards compatibility, it's

# not part of the plugin interface and only something needed for the default

# pass.

# pylint: disable=attribute-defined-outside-init

default_method._approximation_degree = self._approximation_degree

if self.method == "default":

# pylint: disable=attribute-defined-outside-init

plugin_method._approximation_degree = self._approximation_degree

qubit_indices = (

{bit: i for i, bit in enumerate(dag.qubits)}

if plugin_method.supports_coupling_map or default_method.supports_coupling_map

else {}

)

return self._run_main_loop(

dag, qubit_indices, plugin_method, plugin_kwargs, default_method, default_kwargs

)

def _run_main_loop(

self, dag, qubit_indices, plugin_method, plugin_kwargs, default_method, default_kwargs

):

"""Inner loop for the optimizer, after all DAG-independent set-up has been completed."""

for node in dag.op_nodes(ControlFlowOp):

node.op = node.op.replace_blocks(

[

dag_to_circuit(

self._run_main_loop(

circuit_to_dag(block),

{

inner: qubit_indices[outer]

for inner, outer in zip(block.qubits, node.qargs)

},

plugin_method,

plugin_kwargs,

default_method,

default_kwargs,

),

copy_operations=False,

)

for block in node.op.blocks

]

)

for node in dag.named_nodes(*self._synth_gates):

if self._min_qubits is not None and len(node.qargs) < self._min_qubits:

continue

synth_dag = None

unitary = node.op.to_matrix()

n_qubits = len(node.qargs)

if (plugin_method.max_qubits is not None and n_qubits > plugin_method.max_qubits) or (

plugin_method.min_qubits is not None and n_qubits < plugin_method.min_qubits

):

method, kwargs = default_method, default_kwargs

else:

method, kwargs = plugin_method, plugin_kwargs

if method.supports_coupling_map:

kwargs["coupling_map"] = (

self._coupling_map,

[qubit_indices[x] for x in node.qargs],

)

synth_dag = method.run(unitary, **kwargs)

if synth_dag is not None:

dag.substitute_node_with_dag(node, synth_dag)

"""Builds a ``gate_lengths`` dictionary from either ``props`` (BackendV1)

or ``target`` (BackendV2).

The dictionary has the form:

{gate_name: {(qubits,): duration}}

"""

gate_lengths = {}

if target is not None:

for gate, prop_dict in target.items():

gate_lengths[gate] = {}

for qubit, gate_props in prop_dict.items():

if gate_props is not None and gate_props.duration is not None:

gate_lengths[gate][qubit] = gate_props.duration

elif props is not None:

for gate in props._gates:

gate_lengths[gate] = {}

for k, v in props._gates[gate].items():

length = v.get("gate_length")

if length:

gate_lengths[gate][k] = length[0]

if not gate_lengths[gate]:

del gate_lengths[gate]

"""Builds a ``gate_error`` dictionary from either ``props`` (BackendV1)

or ``target`` (BackendV2).

The dictionary has the form:

{gate_name: {(qubits,): error_rate}}

"""

gate_errors = {}

if target is not None:

for gate, prop_dict in target.items():

gate_errors[gate] = {}

for qubit, gate_props in prop_dict.items():

if gate_props is not None and gate_props.error is not None:

gate_errors[gate][qubit] = gate_props.error

if props is not None:

for gate in props._gates:

gate_errors[gate] = {}

for k, v in props._gates[gate].items():

error = v.get("gate_error")

if error:

gate_errors[gate][k] = error[0]

if not gate_errors[gate]:

del gate_errors[gate]

"""

Builds a `gate_lengths` dictionary from either `props` (BackendV1)

or `target (BackendV2)`.

The dictionary has the form:

{(qubits): [Gate, duration]}

"""

gate_lengths = {}

if target is not None and target.qargs is not None:

for qubits in target.qargs:

names = target.operation_names_for_qargs(qubits)

operation_and_durations = []

for name in names:

operation = target.operation_from_name(name)

duration = getattr(target[name].get(qubits, None), "duration", None)

if duration:

operation_and_durations.append((operation, duration))

if operation_and_durations:

gate_lengths[qubits] = operation_and_durations

elif props is not None:

for gate_name, gate_props in props._gates.items():

gate = GateNameToGate[gate_name]

for qubits, properties in gate_props.items():

duration = properties.get("gate_length", [0.0])[0]

operation_and_durations = (gate, duration)

if qubits in gate_lengths:

gate_lengths[qubits].append(operation_and_durations)

else:

gate_lengths[qubits] = [operation_and_durations]

"""

Builds a `gate_error` dictionary from either `props` (BackendV1)

or `target (BackendV2)`.

The dictionary has the form:

{(qubits): [Gate, error]}

"""

gate_errors = {}

if target is not None and target.qargs is not None:

for qubits in target.qargs:

names = target.operation_names_for_qargs(qubits)

operation_and_errors = []

for name in names:

operation = target.operation_from_name(name)

error = getattr(target[name].get(qubits, None), "error", None)

if error:

operation_and_errors.append((operation, error))

if operation_and_errors:

gate_errors[qubits] = operation_and_errors

elif props is not None:

for gate_name, gate_props in props._gates.items():

gate = GateNameToGate[gate_name]

for qubits, properties in gate_props.items():

error = properties.get("gate_error", [0.0])[0]

operation_and_errors = (gate, error)

if qubits in gate_errors:

gate_errors[qubits].append(operation_and_errors)

else:

gate_errors[qubits] = [operation_and_errors]

"""The default unitary synthesis plugin."""

@property

def supports_basis_gates(self):

return True

@property

def supports_coupling_map(self):

return True

@property

def supports_natural_direction(self):

return True

@property

def supports_pulse_optimize(self):

return True

@property

def supports_gate_lengths(self):

return False

@property

def supports_gate_errors(self):

return False

@property

def supports_gate_lengths_by_qubit(self):

return True

@property

def supports_gate_errors_by_qubit(self):

return True

@property

def max_qubits(self):

return None

@property

def min_qubits(self):

return None

@property

def supported_bases(self):

return None

@property

def supports_target(self):

return True

def __init__(self):

super().__init__()

self._decomposer_cache = {}

def _decomposer_2q_from_target(self, target, qubits, approximation_degree):

# we just need 2-qubit decomposers, in any direction.

# we'll fix the synthesis direction later.

qubits_tuple = tuple(sorted(qubits))

reverse_tuple = qubits_tuple[::-1]

if qubits_tuple in self._decomposer_cache:

return self._decomposer_cache[qubits_tuple]

# available instructions on this qubit pair, and their associated property.

available_2q_basis = {}

available_2q_props = {}

# 2q gates sent to 2q decomposers must not have any symbolic parameters. The

# gates must be convertable to a numeric matrix. If a basis gate supports an arbitrary

# angle, we have to choose one angle (or more.)

def _replace_parameterized_gate(op):

if isinstance(op, RXXGate) and isinstance(op.params[0], Parameter):

op = RXXGate(pi / 2)

elif isinstance(op, RZXGate) and isinstance(op.params[0], Parameter):

op = RZXGate(pi / 4)

return op

try:

keys = target.operation_names_for_qargs(qubits_tuple)

for key in keys:

op = target.operation_from_name(key)

if not isinstance(op, Gate):

continue

available_2q_basis[key] = _replace_parameterized_gate(op)

available_2q_props[key] = target[key][qubits_tuple]

except KeyError:

pass

try:

keys = target.operation_names_for_qargs(reverse_tuple)

for key in keys:

if key not in available_2q_basis:

op = target.operation_from_name(key)

if not isinstance(op, Gate):

continue

available_2q_basis[key] = _replace_parameterized_gate(op)

available_2q_props[key] = target[key][reverse_tuple]

except KeyError:

pass

if not available_2q_basis:

raise TranspilerError(

f"Target has no gates available on qubits {qubits} to synthesize over."

)

# available decomposition basis on each of the qubits of the pair

# NOTE: assumes both qubits have the same single-qubit gates

available_1q_basis = _find_matching_euler_bases(target, qubits_tuple[0])

# find all decomposers

# TODO: reduce number of decomposers here somehow

decomposers = []

def is_supercontrolled(gate):

try:

operator = Operator(gate)

except QiskitError:

return False

kak = TwoQubitWeylDecomposition(operator.data)

return isclose(kak.a, pi / 4) and isclose(kak.c, 0.0)

def is_controlled(gate):

try:

operator = Operator(gate)

except QiskitError:

return False

kak = TwoQubitWeylDecomposition(operator.data)

return isclose(kak.b, 0.0) and isclose(kak.c, 0.0)

# possible supercontrolled decomposers (i.e. TwoQubitBasisDecomposer)

supercontrolled_basis = {

k: v for k, v in available_2q_basis.items() if is_supercontrolled(v)

}

for basis_1q, basis_2q in product(available_1q_basis, supercontrolled_basis.keys()):

props = available_2q_props.get(basis_2q)

if props is None:

basis_2q_fidelity = 1.0

else:

error = getattr(props, "error", 0.0)

if error is None:

error = 0.0

basis_2q_fidelity = 1 - error

if approximation_degree is not None:

basis_2q_fidelity *= approximation_degree

decomposer = TwoQubitBasisDecomposer(

supercontrolled_basis[basis_2q],

euler_basis=basis_1q,

basis_fidelity=basis_2q_fidelity,

)

decomposers.append(decomposer)

# If our 2q basis gates are a subset of cx, ecr, or cz then we know TwoQubitBasisDecomposer

# is an ideal decomposition and there is no need to bother calculating the XX embodiments

# or try the XX decomposer

if {"cx", "cz", "ecr"}.issuperset(available_2q_basis):

self._decomposer_cache[qubits_tuple] = decomposers

return decomposers

# possible controlled decomposers (i.e. XXDecomposer)

controlled_basis = {k: v for k, v in available_2q_basis.items() if is_controlled(v)}

basis_2q_fidelity = {}

embodiments = {}

pi2_basis = None

for k, v in controlled_basis.items():

strength = 2 * TwoQubitWeylDecomposition(Operator(v).data).a # pi/2: fully entangling

# each strength has its own fidelity

props = available_2q_props.get(k)

if props is None:

basis_2q_fidelity[strength] = 1.0

else:

error = getattr(props, "error", 0.0)

if error is None:

error = 0.0

basis_2q_fidelity[strength] = 1 - error

# rewrite XX of the same strength in terms of it

embodiment = XXEmbodiments[v.base_class]

if len(embodiment.parameters) == 1:

embodiments[strength] = embodiment.assign_parameters([strength])

else:

embodiments[strength] = embodiment

# basis equivalent to CX are well optimized so use for the pi/2 angle if available

if isclose(strength, pi / 2) and k in supercontrolled_basis:

pi2_basis = v

# if we are using the approximation_degree knob, use it to scale already-given fidelities

if approximation_degree is not None:

basis_2q_fidelity = {k: v * approximation_degree for k, v in basis_2q_fidelity.items()}

if basis_2q_fidelity:

for basis_1q in available_1q_basis:

if isinstance(pi2_basis, CXGate) and basis_1q == "ZSX":

# If we're going to use the pulse optimal decomposition

# in TwoQubitBasisDecomposer we need to compute the basis

# fidelity to use for the decomposition. Either use the

# cx error rate if approximation degree is None, or

# the approximation degree value if it's a float

if approximation_degree is None:

props = target["cx"].get(qubits_tuple)

if props is not None:

fidelity = 1.0 - getattr(props, "error", 0.0)

else:

fidelity = 1.0

else:

fidelity = approximation_degree

pi2_decomposer = TwoQubitBasisDecomposer(

pi2_basis,

euler_basis=basis_1q,

basis_fidelity=fidelity,

pulse_optimize=True,

)

embodiments.update({pi / 2: XXEmbodiments[pi2_decomposer.gate.base_class]})

else:

pi2_decomposer = None

decomposer = XXDecomposer(

basis_fidelity=basis_2q_fidelity,

euler_basis=basis_1q,

embodiments=embodiments,

backup_optimizer=pi2_decomposer,

)

decomposers.append(decomposer)

self._decomposer_cache[qubits_tuple] = decomposers

return decomposers

def run(self, unitary, **options):

# Approximation degree is set directly as an attribute on the

# instance by the UnitarySynthesis pass here as it's not part of

# plugin interface. However if for some reason it's not set assume

# it's 1.

approximation_degree = getattr(self, "_approximation_degree", 1.0)

basis_gates = options["basis_gates"]

coupling_map = options["coupling_map"][0]

natural_direction = options["natural_direction"]

pulse_optimize = options["pulse_optimize"]

gate_lengths = options["gate_lengths_by_qubit"]

gate_errors = options["gate_errors_by_qubit"]

qubits = options["coupling_map"][1]

target = options["target"]

if unitary.shape == (2, 2):

_decomposer1q = Optimize1qGatesDecomposition(basis_gates, target)

sequence = _decomposer1q._resynthesize_run(unitary, qubits[0])

if sequence is None:

return None

return _decomposer1q._gate_sequence_to_dag(sequence)

elif unitary.shape == (4, 4):

# select synthesizers that can lower to the target

if target is not None:

decomposers2q = self._decomposer_2q_from_target(

target, qubits, approximation_degree

)

else:

decomposer2q = _decomposer_2q_from_basis_gates(

basis_gates, pulse_optimize, approximation_degree

)

decomposers2q = [decomposer2q] if decomposer2q is not None else []

# choose the cheapest output among synthesized circuits

synth_circuits = []

for decomposer2q in decomposers2q:

preferred_direction = _preferred_direction(

decomposer2q, qubits, natural_direction, coupling_map, gate_lengths, gate_errors

)

synth_circuit = self._synth_su4(

unitary, decomposer2q, preferred_direction, approximation_degree

)

synth_circuits.append(synth_circuit)

synth_circuit = min(

synth_circuits,

key=partial(_error, target=target, qubits=tuple(qubits)),

default=None,

)

else:

from qiskit.synthesis.unitary.qsd import ( # pylint: disable=cyclic-import

qs_decomposition,

)

# only decompose if needed. TODO: handle basis better

synth_circuit = qs_decomposition(unitary) if (basis_gates or target) else None

if synth_circuit is None:

return None

if isinstance(synth_circuit, DAGCircuit):

return synth_circuit

return circuit_to_dag(synth_circuit)

def _synth_su4(self, su4_mat, decomposer2q, preferred_direction, approximation_degree):

approximate = not approximation_degree == 1.0

synth_circ = decomposer2q(su4_mat, approximate=approximate, use_dag=True)

if not preferred_direction:

return synth_circ

synth_direction = None

# if the gates in synthesis are in the opposite direction of the preferred direction

# resynthesize a new operator which is the original conjugated by swaps.

# this new operator is doubly mirrored from the original and is locally equivalent.

for inst in synth_circ.topological_op_nodes():

if inst.op.num_qubits == 2:

synth_direction = [synth_circ.find_bit(q).index for q in inst.qargs]

if synth_direction is not None and synth_direction != preferred_direction:

su4_mat_mm = su4_mat.copy()

su4_mat_mm[[1, 2]] = su4_mat_mm[[2, 1]]

su4_mat_mm[:, [1, 2]] = su4_mat_mm[:, [2, 1]]

synth_circ = decomposer2q(su4_mat_mm, approximate=approximate, use_dag=True)

out_dag = DAGCircuit()

out_dag.global_phase = synth_circ.global_phase

out_dag.add_qubits(list(reversed(synth_circ.qubits)))

flip_bits = out_dag.qubits[::-1]

for node in synth_circ.topological_op_nodes():

qubits = tuple(flip_bits[synth_circ.find_bit(x).index] for x in node.qargs)

out_dag.apply_operation_back(node.op, qubits, check=False)

return out_dag