Source code for qiskit.transpiler.passes.synthesis.unitary_synthesis

# 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
# 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 (
from qiskit.quantum_info import Operator
from qiskit.circuit import ControlFlowOp, Gate, Parameter
from qiskit.circuit.library.standard_gates import (
from qiskit.transpiler.passes.synthesis import plugin
from qiskit.transpiler.passes.optimization.optimize_1q_decomposition import (
from qiskit.providers.models import BackendProperties
from qiskit.circuit.library.standard_gates import get_standard_gate_name_mapping
from qiskit.exceptions import QiskitError

    "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):
    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()
        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):

    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(
        decomposer2q = XXDecomposer(euler_basis=euler_basis, backup_optimizer=backup_optimizer)
    elif kak_gate is not None:
        decomposer2q = TwoQubitBasisDecomposer(
    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)
            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 (
                    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)

                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 -

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
                cost_0_1 = next(
                    for gate, duration in gate_lengths.get(qubits_tuple, [])
                    if gate == decomposer2q.gate
            except StopIteration:
                cost_1_0 = next(
                    for gate, duration in gate_lengths.get(reverse_tuple, [])
                    if gate == decomposer2q.gate
            except StopIteration:
            if not (cost_0_1 < inf or cost_1_0 < inf):
                    cost_0_1 = next(
                        for gate, error in gate_errors.get(qubits_tuple, [])
                        if gate == decomposer2q.gate
                except StopIteration:
                    cost_1_0 = next(
                        for gate, error in gate_errors.get(reverse_tuple, [])
                        if gate == decomposer2q.gate
                except StopIteration:
            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

[docs]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
[docs] 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 =, **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( 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( 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