# This code is part of Qiskit.
#
# (C) Copyright IBM 2017, 2020.
#
# This code is licensed under the Apache License, Version 2.0. You may
# obtain a copy of this license in the LICENSE.txt file in the root directory
# of this source tree or at http://www.apache.org/licenses/LICENSE-2.0.
#
# Any modifications or derivative works of this code must retain this
# copyright notice, and modified files need to carry a notice indicating
# that they have been altered from the originals.
"""Synthesize UnitaryGates."""
from __future__ import annotations
from math import pi, inf, isclose
from typing import Any
from copy import deepcopy
from itertools import product
from functools import partial
import numpy as np
from qiskit.converters import circuit_to_dag, dag_to_circuit
from qiskit.transpiler import CouplingMap, Target
from qiskit.transpiler.basepasses import TransformationPass
from qiskit.transpiler.exceptions import TranspilerError
from qiskit.dagcircuit.dagcircuit import DAGCircuit
from qiskit.quantum_info.synthesis import one_qubit_decompose
from qiskit.quantum_info.synthesis.xx_decompose import XXDecomposer, XXEmbodiments
from qiskit.quantum_info.synthesis.two_qubit_decompose import (
TwoQubitBasisDecomposer,
TwoQubitWeylDecomposition,
)
from qiskit.quantum_info import Operator
from qiskit.circuit import ControlFlowOp, Gate, Parameter
from qiskit.circuit.library.standard_gates import (
iSwapGate,
CXGate,
CZGate,
RXXGate,
RZXGate,
ECRGate,
)
from qiskit.transpiler.passes.synthesis import plugin
from qiskit.transpiler.passes.optimization.optimize_1q_decomposition import (
Optimize1qGatesDecomposition,
)
from qiskit.providers.models import BackendProperties
from qiskit.circuit.library.standard_gates import get_standard_gate_name_mapping
from qiskit.exceptions import QiskitError
KAK_GATE_NAMES = {
"cx": CXGate(),
"cz": CZGate(),
"iswap": iSwapGate(),
"rxx": RXXGate(pi / 2),
"ecr": ECRGate(),
"rzx": RZXGate(pi / 4), # typically pi/6 is also available
}
GateNameToGate = get_standard_gate_name_mapping()
def _choose_kak_gate(basis_gates):
"""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()]
return kak_gate
def _choose_euler_basis(basis_gates):
"""Choose the first available 1q basis to use in the Euler decomposition."""
basis_set = set(basis_gates or [])
for basis, gates in one_qubit_decompose.ONE_QUBIT_EULER_BASIS_GATES.items():
if set(gates).issubset(basis_set):
return basis
return "U"
def _find_matching_euler_bases(target, qubit):
"""Find matching available 1q basis to use in the Euler decomposition."""
euler_basis_gates = []
basis_set = target.operation_names_for_qargs((qubit,))
for basis, gates in one_qubit_decompose.ONE_QUBIT_EULER_BASIS_GATES.items():
if set(gates).issubset(basis_set):
euler_basis_gates.append(basis)
return euler_basis_gates
def _choose_bases(basis_gates, basis_dict=None):
"""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)
return out_basis
def _decomposer_2q_from_basis_gates(basis_gates, pulse_optimize=None, approximation_degree=None):
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,
)
return decomposer2q
def _error(circuit, target=None, qubits=None):
"""
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:
return len(circuit)
gate_fidelities = []
gate_durations = []
for inst in circuit:
inst_qubits = tuple(qubits[circuit.find_bit(q).index] for q in inst.qubits)
try:
keys = target.operation_names_for_qargs(inst_qubits)
for key in keys:
target_op = target.operation_from_name(key)
if isinstance(target_op, type(inst.operation)) and (
target_op.is_parameterized()
or all(
isclose(float(p1), float(p2))
for p1, p2 in zip(target_op.params, inst.operation.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:
raise TranspilerError(
f"Encountered a bad synthesis. "
f"Target has no {inst.operation} on qubits {qubits}."
) from error
# TODO:return np.sum(gate_durations)
return 1 - np.prod(gate_fidelities)
def _preferred_direction(
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."
)
return preferred_direction
[documentos]class UnitarySynthesis(TransformationPass):
"""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``.
"""
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
[documentos] 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.
Raises:
TranspilerError: if ``method`` was specified for the class and 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`
"""
if self.method != "default" and self.method not in self.plugins.ext_plugins:
raise TranspilerError("Specified method: %s not found in plugin list" % self.method)
# Return fast if we have no synth gates (ie user specified an empty
# list or the synth gates are all in the basis
if not self._synth_gates:
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)
return dag
def _build_gate_lengths(props=None, target=None):
"""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]
return gate_lengths
def _build_gate_errors(props=None, target=None):
"""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]
return gate_errors
def _build_gate_lengths_by_qubit(props=None, target=None):
"""
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]
return gate_lengths
def _build_gate_errors_by_qubit(props=None, target=None):
"""
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]
return gate_errors
class DefaultUnitarySynthesis(plugin.UnitarySynthesisPlugin):
"""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)
# 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[type(v)]
if len(embodiment.parameters) == 1:
embodiments[strength] = embodiment.bind_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":
pi2_decomposer = TwoQubitBasisDecomposer(
pi2_basis,
euler_basis=basis_1q,
basis_fidelity=basis_2q_fidelity,
pulse_optimize=True,
)
embodiments.update({pi / 2: XXEmbodiments[type(pi2_decomposer.gate)]})
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.quantum_info.synthesis.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
synth_dag = circuit_to_dag(synth_circuit) if synth_circuit is not None else None
return synth_dag
def _synth_su4(self, su4_mat, decomposer2q, preferred_direction, approximation_degree):
approximate = not approximation_degree == 1.0
synth_circ = decomposer2q(su4_mat, approximate=approximate)
# 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.
synth_direction = None
for inst in synth_circ:
if inst.operation.num_qubits == 2:
synth_direction = [synth_circ.find_bit(q).index for q in inst.qubits]
if preferred_direction and synth_direction != preferred_direction:
su4_mat_mm = deepcopy(su4_mat)
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).reverse_bits()
return synth_circ