C贸digo fuente para qiskit.primitives.base.base_estimator

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.. estimator-desc:

Overview of Estimator

Estimator class estimates expectation values of quantum circuits and observables.

An estimator is initialized with an empty parameter set. The estimator is used to
create a :class:`~qiskit.providers.JobV1`, via the
:meth:`qiskit.primitives.Estimator.run()` method. This method is called
with the following parameters

* quantum circuits (:math:`\psi_i(\theta)`): list of (parameterized) quantum circuits
  (a list of :class:`~qiskit.circuit.QuantumCircuit` objects).

* observables (:math:`H_j`): a list of :class:`~qiskit.quantum_info.SparsePauliOp`

* parameter values (:math:`\theta_k`): list of sets of values
  to be bound to the parameters of the quantum circuits
  (list of list of float).

The method returns a :class:`~qiskit.providers.JobV1` object, calling
:meth:`qiskit.providers.JobV1.result()` yields the
a list of expectation values plus optional metadata like confidence intervals for
the estimation.

.. math::


Here is an example of how the estimator is used.

.. code-block:: python

    from qiskit.primitives import Estimator
    from qiskit.circuit.library import RealAmplitudes
    from qiskit.quantum_info import SparsePauliOp

    psi1 = RealAmplitudes(num_qubits=2, reps=2)
    psi2 = RealAmplitudes(num_qubits=2, reps=3)

    H1 = SparsePauliOp.from_list([("II", 1), ("IZ", 2), ("XI", 3)])
    H2 = SparsePauliOp.from_list([("IZ", 1)])
    H3 = SparsePauliOp.from_list([("ZI", 1), ("ZZ", 1)])

    theta1 = [0, 1, 1, 2, 3, 5]
    theta2 = [0, 1, 1, 2, 3, 5, 8, 13]
    theta3 = [1, 2, 3, 4, 5, 6]

    estimator = Estimator()

    # calculate [ <psi1(theta1)|H1|psi1(theta1)> ]
    job = estimator.run([psi1], [H1], [theta1])
    job_result = job.result() # It will block until the job finishes.
    print(f"The primitive-job finished with result {job_result}"))

    # calculate [ <psi1(theta1)|H1|psi1(theta1)>,
    #             <psi2(theta2)|H2|psi2(theta2)>,
    #             <psi1(theta3)|H3|psi1(theta3)> ]
    job2 = estimator.run([psi1, psi2, psi1], [H1, H2, H3], [theta1, theta2, theta3])
    job_result = job2.result()
    print(f"The primitive-job finished with result {job_result}")

from __future__ import annotations

from abc import abstractmethod
from collections.abc import Sequence
from copy import copy
from typing import Generic, TypeVar
import typing

from qiskit.circuit import QuantumCircuit
from qiskit.circuit.parametertable import ParameterView
from qiskit.providers import JobV1 as Job
from qiskit.quantum_info.operators import SparsePauliOp
from qiskit.quantum_info.operators.base_operator import BaseOperator

from ..utils import init_observable
from .base_primitive import BasePrimitive

if typing.TYPE_CHECKING:
    from qiskit.opflow import PauliSumOp

T = TypeVar("T", bound=Job)

[documentos]class BaseEstimator(BasePrimitive, Generic[T]): """Estimator base class. Base class for Estimator that estimates expectation values of quantum circuits and observables. """ __hash__ = None def __init__( self, *, options: dict | None = None, ): """ Creating an instance of an Estimator, or using one in a ``with`` context opens a session that holds resources until the instance is ``close()`` ed or the context is exited. Args: options: Default options. """ self._circuits = [] self._observables = [] self._parameters = [] super().__init__(options)
[documentos] def run( self, circuits: Sequence[QuantumCircuit] | QuantumCircuit, observables: Sequence[BaseOperator | PauliSumOp | str] | BaseOperator | PauliSumOp | str, parameter_values: Sequence[Sequence[float]] | Sequence[float] | float | None = None, **run_options, ) -> T: """Run the job of the estimation of expectation value(s). ``circuits``, ``observables``, and ``parameter_values`` should have the same length. The i-th element of the result is the expectation of observable .. code-block:: python obs = observables[i] for the state prepared by .. code-block:: python circ = circuits[i] with bound parameters .. code-block:: python values = parameter_values[i]. Args: circuits: one or more circuit objects. observables: one or more observable objects. Several formats are allowed; importantly, ``str`` should follow the string representation format for :class:`~qiskit.quantum_info.Pauli` objects. parameter_values: concrete parameters to be bound. run_options: runtime options used for circuit execution. Returns: The job object of EstimatorResult. Raises: TypeError: Invalid argument type given. ValueError: Invalid argument values given. """ # Singular validation circuits = self._validate_circuits(circuits) observables = self._validate_observables(observables) parameter_values = self._validate_parameter_values( parameter_values, default=[()] * len(circuits), ) # Cross-validation self._cross_validate_circuits_parameter_values(circuits, parameter_values) self._cross_validate_circuits_observables(circuits, observables) # Options run_opts = copy(self.options) run_opts.update_options(**run_options) return self._run( circuits, observables, parameter_values, **run_opts.__dict__, )
@abstractmethod def _run( self, circuits: tuple[QuantumCircuit, ...], observables: tuple[SparsePauliOp, ...], parameter_values: tuple[tuple[float, ...], ...], **run_options, ) -> T: raise NotImplementedError("The subclass of BaseEstimator must implment `_run` method.") @staticmethod def _validate_observables( observables: Sequence[BaseOperator | PauliSumOp | str] | BaseOperator | PauliSumOp | str, ) -> tuple[SparsePauliOp, ...]: if isinstance(observables, str) or not isinstance(observables, Sequence): observables = (observables,) if len(observables) == 0: raise ValueError("No observables were provided.") return tuple(init_observable(obs) for obs in observables) @staticmethod def _cross_validate_circuits_observables( circuits: tuple[QuantumCircuit, ...], observables: tuple[BaseOperator | PauliSumOp, ...] ) -> None: if len(circuits) != len(observables): raise ValueError( f"The number of circuits ({len(circuits)}) does not match " f"the number of observables ({len(observables)})." ) for i, (circuit, observable) in enumerate(zip(circuits, observables)): if circuit.num_qubits != observable.num_qubits: raise ValueError( f"The number of qubits of the {i}-th circuit ({circuit.num_qubits}) does " f"not match the number of qubits of the {i}-th observable " f"({observable.num_qubits})." ) @property def circuits(self) -> tuple[QuantumCircuit, ...]: """Quantum circuits that represents quantum states. Returns: The quantum circuits. """ return tuple(self._circuits) @property def observables(self) -> tuple[SparsePauliOp, ...]: """Observables to be estimated. Returns: The observables. """ return tuple(self._observables) @property def parameters(self) -> tuple[ParameterView, ...]: """Parameters of the quantum circuits. Returns: Parameters, where ``parameters[i][j]`` is the j-th parameter of the i-th circuit. """ return tuple(self._parameters)