Estimator¶

class Estimator(backend=None, session=None, options=None)[source]¶

Class for interacting with Qiskit Runtime Estimator primitive service.

Qiskit Runtime Estimator primitive service estimates expectation values of quantum circuits and observables.

The run() can be used to submit circuits, observables, and parameters to the Estimator primitive.

You are encouraged to use Session to open a session, during which you can invoke one or more primitives. Jobs submitted within a session are prioritized by the scheduler, and data is cached for efficiency.

Example:

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

from qiskit_ibm_runtime import QiskitRuntimeService, Estimator

service = QiskitRuntimeService(channel="ibm_cloud")

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

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

with Session(service=service, backend="ibmq_qasm_simulator") as session:
    estimator = Estimator(session=session)

    theta1 = [0, 1, 1, 2, 3, 5]

    # calculate [ <psi1(theta1)|H1|psi1(theta1)> ]
    psi1_H1 = estimator.run(circuits=[psi1], observables=[H1], parameter_values=[theta1])
    print(psi1_H1.result())

    # calculate [ <psi1(theta1)|H2|psi1(theta1)>, <psi1(theta1)|H3|psi1(theta1)> ]
    psi1_H23 = estimator.run(
        circuits=[psi1, psi1],
        observables=[H2, H3],
        parameter_values=[theta1]*2
    )
    print(psi1_H23.result())
    # Close the session only if all jobs are finished
    # and you don't need to run more in the session
    session.close()

Initializes the Estimator primitive.

Parameters:

backend (Union[str, IBMBackend, None]) – Backend to run the primitive. This can be a backend name or an IBMBackend instance. If a name is specified, the default account (e.g. QiskitRuntimeService()) is used.
session (Union[Session, str, IBMBackend, None]) –
Session in which to call the primitive.

If both session and backend are specified, session takes precedence. If neither is specified, and the primitive is created inside a qiskit_ibm_runtime.Session context manager, then the session is used. Otherwise if IBM Cloud channel is used, a default backend is selected.
options (Union[Dict, Options, None]) – Primitive options, see Options for detailed description. The backend keyword is still supported but is deprecated.

Attributes

`Estimator.circuits`	Quantum circuits that represents quantum states.
`Estimator.observables`	Observables to be estimated.
`Estimator.options`	Return options values for the sampler.
`Estimator.parameters`	Parameters of the quantum circuits.
`Estimator.session`	Return session used by this primitive.

Methods

`Estimator.run`(circuits, observables[, ...])	Submit a request to the estimator primitive.
`Estimator.set_options`(**fields)	Set options values for the sampler.