qiskit-documentation/docs/api/qiskit-ibm-runtime/0.17/qiskit_ibm_runtime.Estimator.mdx

---
title: Estimator
description: API reference for qiskit_ibm_runtime.Estimator
in_page_toc_min_heading_level: 1
python_api_type: class
python_api_name: qiskit_ibm_runtime.Estimator
---

# Estimator

<Class id="qiskit_ibm_runtime.Estimator" isDedicatedPage={true} github="https://github.com/qiskit/qiskit-ibm-runtime/tree/stable/0.17/qiskit_ibm_runtime/estimator.py" signature="Estimator(backend=None, session=None, options=None)" modifiers="class">
  Class for interacting with Qiskit Runtime Estimator primitive service.

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

  The [`run()`](#qiskit_ibm_runtime.Estimator.run "qiskit_ibm_runtime.Estimator.run") can be used to submit circuits, observables, and parameters to the Estimator primitive.

  You are encouraged to use [`Session`](qiskit_ibm_runtime.Session "qiskit_ibm_runtime.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:

  ```python
  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())
  ```

  Initializes the Estimator primitive.

  **Parameters**

  *   **backend** (`Union`\[`str`, [`IBMBackend`](qiskit_ibm_runtime.IBMBackend "qiskit_ibm_runtime.ibm_backend.IBMBackend"), `None`]) – Backend to run the primitive. This can be a backend name or an [`IBMBackend`](qiskit_ibm_runtime.IBMBackend "qiskit_ibm_runtime.IBMBackend") instance. If a name is specified, the default account (e.g. `QiskitRuntimeService()`) is used.

  *   **session** (`Union`\[[`Session`](qiskit_ibm_runtime.Session "qiskit_ibm_runtime.session.Session"), `str`, [`IBMBackend`](qiskit_ibm_runtime.IBMBackend "qiskit_ibm_runtime.ibm_backend.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`](qiskit_ibm_runtime.Session "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`](qiskit_ibm_runtime.options.Options "qiskit_ibm_runtime.options.options.Options"), `None`]) – Primitive options, see `Options` for detailed description. The `backend` keyword is still supported but is deprecated.

  ## Attributes

  ### circuits

  <Attribute id="qiskit_ibm_runtime.Estimator.circuits">
    Quantum circuits that represents quantum states.

    **Return type**

    `tuple`\[`QuantumCircuit`, `...`]

    **Returns**

    The quantum circuits.
  </Attribute>

  ### observables

  <Attribute id="qiskit_ibm_runtime.Estimator.observables">
    Observables to be estimated.

    **Return type**

    `tuple`\[`SparsePauliOp`, `...`]

    **Returns**

    The observables.
  </Attribute>

  ### options

  <Attribute id="qiskit_ibm_runtime.Estimator.options">
    Return options values for the sampler.

    **Return type**

    `Options`

    **Returns**

    options
  </Attribute>

  ### parameters

  <Attribute id="qiskit_ibm_runtime.Estimator.parameters">
    Parameters of the quantum circuits.

    **Return type**

    `tuple`\[`ParameterView`, `...`]

    **Returns**

    Parameters, where `parameters[i][j]` is the j-th parameter of the i-th circuit.
  </Attribute>

  ### session

  <Attribute id="qiskit_ibm_runtime.Estimator.session">
    Return session used by this primitive.

    **Return type**

    `Optional`\[[`Session`](qiskit_ibm_runtime.Session "qiskit_ibm_runtime.session.Session")]

    **Returns**

    Session used by this primitive, or `None` if session is not used.
  </Attribute>

  ## Methods

  ### run

  <Function id="qiskit_ibm_runtime.Estimator.run" signature="run(circuits, observables, parameter_values=None, **kwargs)">
    Submit a request to the estimator primitive.

    **Parameters**

    *   **circuits** (*QuantumCircuit | Sequence\[QuantumCircuit]*) – a (parameterized) `QuantumCircuit` or a list of (parameterized) `QuantumCircuit`.
    *   **observables** (*BaseOperator | PauliSumOp | Sequence\[BaseOperator | PauliSumOp]*) – Observable objects.
    *   **parameter\_values** (*Sequence\[float] | Sequence\[Sequence\[float]] | None*) – Concrete parameters to be bound.
    *   **\*\*kwargs** – Individual options to overwrite the default primitive options. These include the runtime options in [`qiskit_ibm_runtime.RuntimeOptions`](qiskit_ibm_runtime.RuntimeOptions "qiskit_ibm_runtime.RuntimeOptions").

    **Return type**

    [RuntimeJob](qiskit_ibm_runtime.RuntimeJob "qiskit_ibm_runtime.RuntimeJob")

    **Returns**

    Submitted job. The result of the job is an instance of `qiskit.primitives.EstimatorResult`.

    **Raises**

    **ValueError** – Invalid arguments are given.
  </Function>

  ### set\_options

  <Function id="qiskit_ibm_runtime.Estimator.set_options" signature="set_options(**fields)">
    Set options values for the sampler.

    **Parameters**

    **\*\*fields** – The fields to update the options

    **Return type**

    `None`
  </Function>
</Class>