text: # -*- coding: utf-8 -*-
  
  # This code is part of Qiskit.
  #
  # (C) Copyright IBM 2017, 2018.
  #
  # 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.
  
  """Backend Configuration Classes."""
  import re
  import copy
  import warnings
  from types import SimpleNamespace
  from typing import Dict, List, Any, Iterable, Union
  from collections import defaultdict
  
  from qiskit.exceptions import QiskitError
  from qiskit.providers.exceptions import BackendConfigurationError
  from qiskit.pulse.channels import (Channel, DriveChannel, MeasureChannel,
                                     ControlChannel, AcquireChannel)
  
  
  class GateConfig:
      """Class representing a Gate Configuration
  
      Attributes:
          name: the gate name as it will be referred to in Qasm.
          parameters: variable names for the gate parameters (if any).
          qasm_def: definition of this gate in terms of Qasm primitives U
                    and CX.
      """
  
      def __init__(self, name, parameters, qasm_def, coupling_map=None,
                   latency_map=None, conditional=None, description=None):
          """Initialize a GateConfig object
  
          Args:
              name (str): the gate name as it will be referred to in Qasm.
              parameters (list): variable names for the gate parameters (if any)
                                 as a list of strings.
              qasm_def (str): definition of this gate in terms of Qasm primitives
                              U and CX.
              coupling_map (list): An optional coupling map for the gate. In
                  the form of a list of lists of integers representing the qubit
                  groupings which are coupled by this gate.
              latency_map (list): An optional map of latency for the gate. In the
                  the form of a list of lists of integers of either 0 or 1
                  representing an array of dimension
                  len(coupling_map) X n_registers that specifies the register
                  latency (1: fast, 0: slow) conditional operations on the gate
              conditional (bool): Optionally specify whether this gate supports
                  conditional operations (true/false). If this is not specified,
                  then the gate inherits the conditional property of the backend.
              description (str): Description of the gate operation
          """
  
          self.name = name
          self.parameters = parameters
          self.qasm_def = qasm_def
          # coupling_map with length 0 is invalid
          if coupling_map:
              self.coupling_map = coupling_map
          # latency_map with length 0 is invalid
          if latency_map:
              self.latency_map = latency_map
          if conditional is not None:
              self.conditional = conditional
          if description is not None:
              self.description = description
  
      @classmethod
      def from_dict(cls, data):
          """Create a new GateConfig object from a dictionary.
  
          Args:
              data (dict): A dictionary representing the GateConfig to create.
                           It will be in the same format as output by
                           :func:`to_dict`.
  
          Returns:
              GateConfig: The GateConfig from the input dictionary.
          """
          return cls(**data)
  
      def to_dict(self):
          """Return a dictionary format representation of the GateConfig.
  
          Returns:
              dict: The dictionary form of the GateConfig.
          """
          out_dict = {
              'name': self.name,
              'parameters': self.parameters,
              'qasm_def': self.qasm_def,
          }
          if hasattr(self, 'coupling_map'):
              out_dict['coupling_map'] = self.coupling_map
          if hasattr(self, 'latency_map'):
              out_dict['latency_map'] = self.latency_map
          if hasattr(self, 'conditional'):
              out_dict['conditional'] = self.conditional
          if hasattr(self, 'description'):
              out_dict['description'] = self.description
          return out_dict
  
      def __eq__(self, other):
          if isinstance(other, GateConfig):
              if self.to_dict() == other.to_dict():
                  return True
          return False
  
      def __repr__(self):
          out_str = "GateConfig(%s, %s, %s" % (self.name, self.parameters,
                                               self.qasm_def)
          for i in ['coupling_map', 'latency_map', 'conditional', 'description']:
              if hasattr(self, i):
                  out_str += ', ' + repr(getattr(self, i))
          out_str += ')'
          return out_str
  
  
  class UchannelLO:
      """Class representing a U Channel LO
  
      Attributes:
          q: Qubit that scale corresponds too.
          scale: Scale factor for qubit frequency.
      """
  
      def __init__(self, q, scale):
          """Initialize a UchannelLOSchema object
  
          Args:
              q (int): Qubit that scale corresponds too. Must be >= 0.
              scale (complex): Scale factor for qubit frequency.
  
          Raises:
              QiskitError: If q is < 0
          """
          if q < 0:
              raise QiskitError('q must be >=0')
          self.q = q
          self.scale = scale
  
      @classmethod
      def from_dict(cls, data):
          """Create a new UchannelLO object from a dictionary.
  
          Args:
              data (dict): A dictionary representing the UChannelLO to
                  create. It will be in the same format as output by
                  :func:`to_dict`.
  
          Returns:
              UchannelLO: The UchannelLO from the input dictionary.
          """
          return cls(**data)
  
      def to_dict(self):
          """Return a dictionary format representation of the UChannelLO.
  
          Returns:
              dict: The dictionary form of the UChannelLO.
          """
          out_dict = {
              'q': self.q,
              'scale': self.scale,
          }
          return out_dict
  
      def __eq__(self, other):
          if isinstance(other, UchannelLO):
              if self.to_dict() == other.to_dict():
                  return True
          return False
  
      def __repr__(self):
          return "UchannelLO(%s, %s)" % (self.q, self.scale)
  
  
  class QasmBackendConfiguration(SimpleNamespace):
      """Class representing a Qasm Backend Configuration.
  
      Attributes:
          backend_name: backend name.
          backend_version: backend version in the form X.Y.Z.
          n_qubits: number of qubits.
          basis_gates: list of basis gates names on the backend.
          gates: list of basis gates on the backend.
          local: backend is local or remote.
          simulator: backend is a simulator.
          conditional: backend supports conditional operations.
          open_pulse: backend supports open pulse.
          memory: backend supports memory.
          max_shots: maximum number of shots supported.
      """
  
      def __init__(self, backend_name, backend_version, n_qubits,
                   basis_gates, gates, local, simulator,
                   conditional, open_pulse, memory,
                   max_shots, coupling_map, max_experiments=None,
                   sample_name=None, n_registers=None, register_map=None,
                   configurable=None, credits_required=None, online_date=None,
                   display_name=None, description=None, tags=None, **kwargs):
          """Initialize a QasmBackendConfiguration Object
  
          Args:
              backend_name (str): The backend name
              backend_version (str): The backend version in the form X.Y.Z
              n_qubits (int): the number of qubits for the backend
              basis_gates (list): The list of strings for the basis gates of the
                  backends
              gates (list): The list of GateConfig objects for the basis gates of
                  the backend
              local (bool): True if the backend is local or False if remote
              simulator (bool): True if the backend is a simulator
              conditional (bool): True if the backend supports conditional
                  operations
              open_pulse (bool): True if the backend supports OpenPulse
              memory (bool): True if the backend supports memory
              max_shots (int): The maximum number of shots allowed on the backend
              coupling_map (list): The coupling map for the device
              max_experiments (int): The maximum number of experiments per job
              sample_name (str): Sample name for the backend
              n_registers (int): Number of register slots available for feedback
                  (if conditional is True)
              register_map (list): An array of dimension n_qubits X
                  n_registers that specifies whether a qubit can store a
                  measurement in a certain register slot.
              configurable (bool): True if the backend is configurable, if the
                  backend is a simulator
              credits_required (bool): True if backend requires credits to run a
                  job.
              online_date (datetime): The date that the device went online
              display_name (str): Alternate name field for the backend
              description (str): A description for the backend
              tags (list): A list of string tags to describe the backend
              **kwargs: optional fields
          """
  
          self.backend_name = backend_name
          self.backend_version = backend_version
          self.n_qubits = n_qubits
          self.basis_gates = basis_gates
          self.gates = gates
          self.local = local
          self.simulator = simulator
          self.conditional = conditional
          self.open_pulse = open_pulse
          self.memory = memory
          self.max_shots = max_shots
          self.coupling_map = coupling_map
          # max_experiments must be >=1
          if max_experiments:
              self.max_experiments = max_experiments
          if sample_name is not None:
              self.sample_name = sample_name
          # n_registers must be >=1
          if n_registers:
              self.n_registers = 1
          # register_map must have at least 1 entry
          if register_map:
              self.register_map = register_map
          if configurable is not None:
              self.configurable = configurable
          if credits_required is not None:
              self.credits_required = credits_required
          if online_date is not None:
              self.online_date = online_date
          if display_name is not None:
              self.display_name = display_name
          if description is not None:
              self.description = description
          if tags is not None:
              self.tags = tags
  
          # Add pulse properties here becuase some backends do not
          # fit within the Qasm / Pulse backend partitioning in Qiskit
          if 'dt' in kwargs.keys():
              kwargs['dt'] *= 1e-9
          if 'dtm' in kwargs.keys():
              kwargs['dtm'] *= 1e-9
  
          if 'qubit_lo_range' in kwargs.keys():
              kwargs['qubit_lo_range'] = [[min_range * 1e9, max_range * 1e9] for
                                          (min_range, max_range) in kwargs['qubit_lo_range']]
  
          if 'meas_lo_range' in kwargs.keys():
              kwargs['meas_lo_range'] = [[min_range * 1e9, max_range * 1e9] for
                                         (min_range, max_range) in kwargs['meas_lo_range']]
  
          # convert rep_times from μs to sec
          if 'rep_times' in kwargs.keys():
              kwargs['rep_times'] = [_rt * 1e-6 for _rt in kwargs['rep_times']]
  
          self.__dict__.update(kwargs)
  
      def __getstate__(self):
          return self.to_dict()
  
      def __setstate__(self, state):
          return self.from_dict(state)
  
      def __reduce__(self):
          return (self.__class__, (self.backend_name, self.backend_version,
                                   self.n_qubits, self.basis_gates, self.gates,
                                   self.local, self.simulator, self.conditional,
                                   self.open_pulse, self.memory, self.max_shots,
                                   self.coupling_map))
  
      @classmethod
      def from_dict(cls, data):
          """Create a new GateConfig object from a dictionary.
  
          Args:
              data (dict): A dictionary representing the GateConfig to create.
                           It will be in the same format as output by
                           :func:`to_dict`.
  
          Returns:
              GateConfig: The GateConfig from the input dictionary.
          """
          in_data = copy.copy(data)
          gates = [GateConfig.from_dict(x) for x in in_data.pop('gates')]
          in_data['gates'] = gates
          return cls(**in_data)
  
      def to_dict(self):
          """Return a dictionary format representation of the GateConfig.
  
          Returns:
              dict: The dictionary form of the GateConfig.
          """
          out_dict = copy.copy(self.__dict__)
          out_dict['gates'] = [x.to_dict() for x in self.gates]
          return out_dict
  
      @property
      def num_qubits(self):
          """Returns the number of qubits.
  
          In future, `n_qubits` should be replaced in favor of `num_qubits` for consistent use
          throughout Qiskit. Until this is properly refactored, this property serves as intermediate
          solution.
          """
          return self.n_qubits
  
      def __eq__(self, other):
          if isinstance(other, QasmBackendConfiguration):
              if self.to_dict() == other.to_dict():
                  return True
          return False
  
      def __contains__(self, item):
          return item in self.__dict__
  
  
  class BackendConfiguration(QasmBackendConfiguration):
      """Backwards compat shim representing an abstract backend configuration."""
      pass
  
  
  class PulseBackendConfiguration(QasmBackendConfiguration):
      """Static configuration state for an OpenPulse enabled backend. This contains information
      about the set up of the device which can be useful for building Pulse programs.
      """
  
      def __init__(self,
                   backend_name: str,
                   backend_version: str,
                   n_qubits: int,
                   basis_gates: List[str],
                   gates: GateConfig,
                   local: bool,
                   simulator: bool,
                   conditional: bool,
                   open_pulse: bool,
                   memory: bool,
                   max_shots: int,
                   coupling_map,
                   n_uchannels: int,
                   u_channel_lo: List[List[UchannelLO]],
                   meas_levels: List[int],
                   qubit_lo_range: List[List[float]],
                   meas_lo_range: List[List[float]],
                   dt: float,
                   dtm: float,
                   rep_times: List[float],
                   meas_kernels: List[str],
                   discriminators: List[str],
                   rep_delays: List[float] = None,
                   dynamic_reprate_enabled: bool = False,
                   hamiltonian: Dict[str, str] = None,
                   channel_bandwidth=None,
                   acquisition_latency=None,
                   conditional_latency=None,
                   meas_map=None,
                   max_experiments=None,
                   sample_name=None,
                   n_registers=None,
                   register_map=None,
                   configurable=None,
                   credits_required=None,
                   online_date=None,
                   display_name=None,
                   description=None,
                   tags=None,
                   channels: Dict[str, Any] = None,
                   **kwargs):
          """
          Initialize a backend configuration that contains all the extra configuration that is made
          available for OpenPulse backends.
  
          Args:
              backend_name: backend name.
              backend_version: backend version in the form X.Y.Z.
              n_qubits: number of qubits.
              basis_gates: list of basis gates names on the backend.
              gates: list of basis gates on the backend.
              local: backend is local or remote.
              simulator: backend is a simulator.
              conditional: backend supports conditional operations.
              open_pulse: backend supports open pulse.
              memory: backend supports memory.
              max_shots: maximum number of shots supported.
              coupling_map (list): The coupling map for the device
              n_uchannels: Number of u-channels.
              u_channel_lo: U-channel relationship on device los.
              meas_levels: Supported measurement levels.
              qubit_lo_range: Qubit lo ranges for each qubit with form (min, max) in GHz.
              meas_lo_range: Measurement lo ranges for each qubit with form (min, max) in GHz.
              dt: Qubit drive channel timestep in nanoseconds.
              dtm: Measurement drive channel timestep in nanoseconds.
              rep_times: Supported repetition times (program execution time) for backend in μs.
              meas_kernels: Supported measurement kernels.
              discriminators: Supported discriminators.
              rep_delays: Supported repetition delays (delay between programs) for backend in μs.
                  Optional, but will be specified when ``dynamic_reprate_enabled=True``.
              dynamic_reprate_enabled: whether delay between programs can be set dynamically
                  (ie via ``rep_delay``). Defaults to False.
              hamiltonian: An optional dictionary with fields characterizing the system hamiltonian.
              channel_bandwidth (list): Bandwidth of all channels
                  (qubit, measurement, and U)
              acquisition_latency (list): Array of dimension
                  n_qubits x n_registers. Latency (in units of dt) to write a
                  measurement result from qubit n into register slot m.
              conditional_latency (list): Array of dimension n_channels
                  [d->u->m] x n_registers. Latency (in units of dt) to do a
                  conditional operation on channel n from register slot m
              meas_map (list): Grouping of measurement which are multiplexed
              max_experiments (int): The maximum number of experiments per job
              sample_name (str): Sample name for the backend
              n_registers (int): Number of register slots available for feedback
                  (if conditional is True)
              register_map (list): An array of dimension n_qubits X
                  n_registers that specifies whether a qubit can store a
                  measurement in a certain register slot.
              configurable (bool): True if the backend is configurable, if the
                  backend is a simulator
              credits_required (bool): True if backend requires credits to run a
                  job.
              online_date (datetime): The date that the device went online
              display_name (str): Alternate name field for the backend
              description (str): A description for the backend
              tags (list): A list of string tags to describe the backend
              channels: An optional dictionary containing information of each channel -- their
                  purpose, type, and qubits operated on.
              **kwargs: Optional fields.
          """
          self.n_uchannels = n_uchannels
          self.u_channel_lo = u_channel_lo
          self.meas_levels = meas_levels
          self.qubit_lo_range = [[min_range * 1e9, max_range * 1e9] for
                                 (min_range, max_range) in qubit_lo_range]
          self.meas_lo_range = [[min_range * 1e9, max_range * 1e9] for
                                (min_range, max_range) in meas_lo_range]
          self.meas_kernels = meas_kernels
          self.discriminators = discriminators
          self.hamiltonian = hamiltonian
  
          self.dynamic_reprate_enabled = dynamic_reprate_enabled
  
          self.rep_times = [_rt * 1e-6 for _rt in rep_times]  # convert to sec
          # if ``rep_delays`` not specified, leave as None
          self.rep_delays = None
          if rep_delays:
              self.rep_delays = [_rd * 1e-6 for _rd in rep_delays]  # convert to sec
          self.dt = dt * 1e-9  # pylint: disable=invalid-name
          self.dtm = dtm * 1e-9
  
          if channels is not None:
              self.channels = channels
  
              (self._qubit_channel_map,
               self._channel_qubit_map,
               self._control_channels) = self._parse_channels(channels=channels)
  
          if channel_bandwidth is not None:
              self.channel_bandwidth = [[min_range * 1e9, max_range * 1e9] for
                                        (min_range, max_range) in channel_bandwidth]
          if acquisition_latency is not None:
              self.acquisition_latency = acquisition_latency
          if conditional_latency is not None:
              self.conditional_latency = conditional_latency
          if meas_map is not None:
              self.meas_map = meas_map
          super().__init__(backend_name=backend_name, backend_version=backend_version,
                           n_qubits=n_qubits, basis_gates=basis_gates, gates=gates,
                           local=local, simulator=simulator, conditional=conditional,
                           open_pulse=open_pulse, memory=memory, max_shots=max_shots,
                           coupling_map=coupling_map, max_experiments=max_experiments,
                           sample_name=sample_name, n_registers=n_registers,
                           register_map=register_map, configurable=configurable,
                           credits_required=credits_required, online_date=online_date,
                           display_name=display_name, description=description,
                           tags=tags, **kwargs)
  
      @classmethod
      def from_dict(cls, data):
          """Create a new GateConfig object from a dictionary.
  
          Args:
              data (dict): A dictionary representing the GateConfig to create.
                           It will be in the same format as output by
                           :func:`to_dict`.
  
          Returns:
              GateConfig: The GateConfig from the input dictionary.
          """
          in_data = copy.copy(data)
          gates = [GateConfig.from_dict(x) for x in in_data.pop('gates')]
          in_data['gates'] = gates
          input_uchannels = in_data.pop('u_channel_lo')
          u_channels = []
          for channel in input_uchannels:
              u_channels.append([UchannelLO.from_dict(x) for x in channel])
          in_data['u_channel_lo'] = u_channels
          return cls(**in_data)
  
      def to_dict(self):
          """Return a dictionary format representation of the GateConfig.
  
          Returns:
              dict: The dictionary form of the GateConfig.
          """
          out_dict = super().to_dict()
          u_channel_lo = []
          for x in self.u_channel_lo:
              channel = []
              for y in x:
                  channel.append(y.to_dict())
              u_channel_lo.append(channel)
          out_dict.update({
              'n_uchannels': self.n_uchannels,
              'u_channel_lo': u_channel_lo,
              'meas_levels': self.meas_levels,
              'qubit_lo_range': self.qubit_lo_range,
              'meas_lo_range': self.meas_lo_range,
              'meas_kernels': self.meas_kernels,
              'discriminators': self.discriminators,
              'hamiltonian': self.hamiltonian,
              'rep_times': self.rep_times,
              'dt': self.dt,
              'dtm': self.dtm,
          })
          if hasattr(self, 'rep_delays'):
              out_dict['rep_delays'] = self.rep_delays
          if hasattr(self, 'dynamic_reprate_enabled'):
              out_dict['dynamic_reprate_enabled'] = self.dynamic_reprate_enabled
          if hasattr(self, 'channel_bandwidth'):
              out_dict['channel_bandwidth'] = self.channel_bandwidth
          if hasattr(self, 'meas_map'):
              out_dict['meas_map'] = self.meas_map
          if hasattr(self, 'acquisition_latency'):
              out_dict['acquisition_latency'] = self.acquisition_latency
          if hasattr(self, 'conditional_latency'):
              out_dict['conditional_latency'] = self.conditional_latency
          if 'channels' in out_dict:
              out_dict.pop('_qubit_channel_map')
              out_dict.pop('_channel_qubit_map')
              out_dict.pop('_control_channels')
          return out_dict
  
      def __eq__(self, other):
          if isinstance(other, QasmBackendConfiguration):
              if self.to_dict() == other.to_dict():
                  return True
          return False
  
      @property
      def sample_rate(self) -> float:
          """Sample rate of the signal channels in Hz (1/dt)."""
          return 1.0 / self.dt
  
      def drive(self, qubit: int) -> DriveChannel:
          """
          Return the drive channel for the given qubit.
  
          Raises:
              BackendConfigurationError: If the qubit is not a part of the system.
          Returns:
              Qubit drive channel.
          """
          if not 0 <= qubit < self.n_qubits:
              raise BackendConfigurationError("Invalid index for {}-qubit system.".format(qubit))
          return DriveChannel(qubit)
  
      def measure(self, qubit: int) -> MeasureChannel:
          """
          Return the measure stimulus channel for the given qubit.
  
          Raises:
              BackendConfigurationError: If the qubit is not a part of the system.
          Returns:
              Qubit measurement stimulus line.
          """
          if not 0 <= qubit < self.n_qubits:
              raise BackendConfigurationError("Invalid index for {}-qubit system.".format(qubit))
          return MeasureChannel(qubit)
  
      def acquire(self, qubit: int) -> AcquireChannel:
          """
          Return the acquisition channel for the given qubit.
  
          Raises:
              BackendConfigurationError: If the qubit is not a part of the system.
          Returns:
              Qubit measurement acquisition line.
          """
          if not 0 <= qubit < self.n_qubits:
              raise BackendConfigurationError("Invalid index for {}-qubit systems.".format(qubit))
          return AcquireChannel(qubit)
  
      def control(self, qubits: Iterable[int] = None,
                  channel: int = None) -> List[ControlChannel]:
          """
          Return the secondary drive channel for the given qubit -- typically utilized for
          controlling multiqubit interactions. This channel is derived from other channels.
  
          Args:
              qubits: Tuple or list of qubits of the form `(control_qubit, target_qubit)`.
              channel: Deprecated.
  
          Raises:
              BackendConfigurationError: If the ``qubits`` is not a part of the system or if
                  the backend does not provide `channels` information in its configuration.
  
          Returns:
              List of control channels.
          """
          if channel is not None:
              warnings.warn('The channel argument has been deprecated in favor of qubits. '
                            'This method will now return accurate ControlChannels determined '
                            'by qubit indices.',
                            DeprecationWarning)
              qubits = [channel]
          try:
              if isinstance(qubits, list):
                  qubits = tuple(qubits)
              return self._control_channels[qubits]
          except KeyError:
              raise BackendConfigurationError("Couldn't find the ControlChannel operating on qubits "
                                              "{} on {}-qubit system. The ControlChannel information"
                                              " is retrieved from the "
                                              " backend.".format(qubits, self.n_qubits))
          except AttributeError:
              raise BackendConfigurationError("This backend - '{}' does not provide channel "
                                              "information.".format(self.backend_name))
  
      def get_channel_qubits(self, channel: Channel) -> List[int]:
          """
          Return a list of indices for qubits which are operated on directly by the given ``channel``.
  
          Raises:
              BackendConfigurationError: If ``channel`` is not a found or if
                  the backend does not provide `channels` information in its configuration.
  
          Returns:
              List of qubits operated on my the given ``channel``.
          """
          try:
              return self._channel_qubit_map[channel]
          except KeyError:
              raise BackendConfigurationError("Couldn't find the Channel - {}".format(channel))
          except AttributeError:
              raise BackendConfigurationError("This backend - '{}' does not provide channel "
                                              "information.".format(self.backend_name))
  
      def get_qubit_channels(self, qubit: Union[int, Iterable[int]]) -> List[Channel]:
          r"""Return a list of channels which operate on the given ``qubit``.
  
          Raises:
              BackendConfigurationError: If ``qubit`` is not a found or if
                  the backend does not provide `channels` information in its configuration.
  
          Returns:
              List of ``Channel``\s operated on my the given ``qubit``.
          """
          channels = set()
          try:
              if isinstance(qubit, int):
                  for key in self._qubit_channel_map.keys():
                      if qubit in key:
                          channels.update(self._qubit_channel_map[key])
                  if len(channels) == 0:
                      raise KeyError
              elif isinstance(qubit, list):
                  qubit = tuple(qubit)
                  channels.update(self._qubit_channel_map[qubit])
              elif isinstance(qubit, tuple):
                  channels.update(self._qubit_channel_map[qubit])
              return list(channels)
          except KeyError:
              raise BackendConfigurationError("Couldn't find the qubit - {}".format(qubit))
          except AttributeError:
              raise BackendConfigurationError("This backend - '{}' does not provide channel "
                                              "information.".format(self.backend_name))
  
      def describe(self, channel: ControlChannel) -> Dict[DriveChannel, complex]:
          """
          Return a basic description of the channel dependency. Derived channels are given weights
          which describe how their frames are linked to other frames.
          For instance, the backend could be configured with this setting::
  
              u_channel_lo = [
                  [UchannelLO(q=0, scale=1. + 0.j)],
                  [UchannelLO(q=0, scale=-1. + 0.j), UchannelLO(q=1, scale=1. + 0.j)]
              ]
  
          Then, this method can be used as follows::
  
              backend.configuration().describe(ControlChannel(1))
              >>> {DriveChannel(0): -1, DriveChannel(1): 1}
  
          Args:
              channel: The derived channel to describe.
          Raises:
              BackendConfigurationError: If channel is not a ControlChannel.
          Returns:
              Control channel derivations.
          """
          if not isinstance(channel, ControlChannel):
              raise BackendConfigurationError("Can only describe ControlChannels.")
          result = {}
          for u_chan_lo in self.u_channel_lo[channel.index]:
              result[DriveChannel(u_chan_lo.q)] = u_chan_lo.scale
          return result
  
      def _parse_channels(self, channels: Dict[set, Any]) -> Dict[Any, Any]:
          r"""
          Generates a dictionaries of ``Channel``\s, and tuple of qubit(s) they operate on.
  
          Args:
              channels: An optional dictionary containing information of each channel -- their
                  purpose, type, and qubits operated on.
  
          Returns:
              qubit_channel_map: Dictionary mapping tuple of qubit(s) to list of ``Channel``\s.
              channel_qubit_map: Dictionary mapping ``Channel`` to list of qubit(s).
              control_channels: Dictionary mapping tuple of qubit(s), to list of
                  ``ControlChannel``\s.
          """
          qubit_channel_map = defaultdict(list)
          channel_qubit_map = defaultdict(list)
          control_channels = defaultdict(list)
          channels_dict = {
              DriveChannel.prefix: DriveChannel,
              ControlChannel.prefix: ControlChannel,
              MeasureChannel.prefix: MeasureChannel,
              'acquire': AcquireChannel
          }
          for channel, config in channels.items():
              channel_prefix, index = self._get_channel_prefix_index(channel)
              channel_type = channels_dict[channel_prefix]
              qubits = tuple(config['operates']['qubits'])
              if channel_prefix in channels_dict:
                  qubit_channel_map[qubits].append(channel_type(index))
                  channel_qubit_map[(channel_type(index))].extend(list(qubits))
                  if channel_prefix == ControlChannel.prefix:
                      control_channels[qubits].append(channel_type(index))
          return dict(qubit_channel_map), dict(channel_qubit_map), dict(control_channels)
  
      def _get_channel_prefix_index(self, channel: str) -> str:
          """Return channel prefix and index from the given ``channel``.
  
          Args:
              channel: Name of channel.
  
          Raises:
              BackendConfigurationError: If invalid channel name is found.
  
          Return:
              Channel name and index. For example, if ``channel=acquire0``, this method
              returns ``acquire`` and ``0``.
          """
          channel_prefix = re.match(r"(?P<channel>[a-z]+)(?P<index>[0-9]+)", channel)
          try:
              return channel_prefix.group('channel'), int(channel_prefix.group('index'))
          except AttributeError:
              raise BackendConfigurationError("Invalid channel name - '{}' found.".format(channel))
  