---
title: BaseEstimatorV1 (v1.3)
description: API reference for qiskit.primitives.BaseEstimatorV1 in qiskit v1.3
source: https://quantum.cloud.ibm.com/docs/en/api/qiskit/1.3/qiskit.primitives.BaseEstimatorV1
---

# BaseEstimatorV1

*class* `qiskit.primitives.BaseEstimatorV1(*, options=None)`

[GitHub](https://github.com/Qiskit/qiskit/tree/stable/1.3/qiskit/primitives/base/base_estimator.py#L42-L188)

Bases: `BasePrimitive`, [`Generic`](https://docs.python.org/3/library/typing.html#typing.Generic)\[`T`]

Estimator V1 base class.

Base class for Estimator that estimates expectation values of quantum circuits and observables.

An estimator is initialized with an empty parameter set. The estimator is used to create a [`JobV1`](/docs/api/qiskit/1.3/qiskit.providers.JobV1 "qiskit.providers.JobV1"), via the [`qiskit.primitives.Estimator.run()`](/docs/api/qiskit/1.3/qiskit.primitives.Estimator#run "qiskit.primitives.Estimator.run") method. This method is called with the following parameters

- quantum circuits ($\psi_i(\theta)$): list of (parameterized) quantum circuits (a list of [`QuantumCircuit`](/docs/api/qiskit/1.3/qiskit.circuit.QuantumCircuit "qiskit.circuit.QuantumCircuit") objects).
- observables ($H_j$): a list of [`SparsePauliOp`](/docs/api/qiskit/1.3/qiskit.quantum_info.SparsePauliOp "qiskit.quantum_info.SparsePauliOp") objects.
- parameter values ($\theta_k$): list of sets of values to be bound to the parameters of the quantum circuits (list of list of float).

The method returns a [`JobV1`](/docs/api/qiskit/1.3/qiskit.providers.JobV1 "qiskit.providers.JobV1") object, calling [`qiskit.providers.JobV1.result()`](/docs/api/qiskit/1.3/qiskit.providers.JobV1#result "qiskit.providers.JobV1.result") yields the a list of expectation values plus optional metadata like confidence intervals for the estimation.

$$
\langle\psi_i(\theta_k)|H_j|\psi_i(\theta_k)\rangle
$$

Here is an example of how the estimator is used.

```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}")
```

Creating an instance of an Estimator V1, or using one in a `with` context opens a session that holds resources until the instance is `close()` ed or the context is exited.

**Parameters**

**options** ([*dict*](https://docs.python.org/3/library/stdtypes.html#dict) *| None*) – Default options.

## Attributes

### options

Return options values for the estimator.

**Returns**

options

## Methods

### run

`run(circuits, observables, parameter_values=None, **run_options)`

[GitHub](https://github.com/Qiskit/qiskit/tree/stable/1.3/qiskit/primitives/base/base_estimator.py#L121-L178)

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

```python
obs = observables[i]
```

for the state prepared by

```python
circ = circuits[i]
```

with bound parameters

```python
values = parameter_values[i]
```

**Parameters**

- **circuits** (*Sequence\[*[*QuantumCircuit*](/docs/api/qiskit/1.3/qiskit.circuit.QuantumCircuit "qiskit.circuit.QuantumCircuit")*] |* [*QuantumCircuit*](/docs/api/qiskit/1.3/qiskit.circuit.QuantumCircuit "qiskit.circuit.QuantumCircuit")) – one or more circuit objects.
- **observables** (*Sequence\[BaseOperator |* [*str*](https://docs.python.org/3/library/stdtypes.html#str)*] | BaseOperator |* [*str*](https://docs.python.org/3/library/stdtypes.html#str)) – one or more observable objects. Several formats are allowed; importantly, `str` should follow the string representation format for [`Pauli`](/docs/api/qiskit/1.3/qiskit.quantum_info.Pauli "qiskit.quantum_info.Pauli") objects.
- **parameter\_values** (*Sequence\[Sequence\[*[*float*](https://docs.python.org/3/library/functions.html#float)*]] | Sequence\[*[*float*](https://docs.python.org/3/library/functions.html#float)*] |* [*float*](https://docs.python.org/3/library/functions.html#float) *| None*) – concrete parameters to be bound.
- **run\_options** – runtime options used for circuit execution.

**Returns**

The job object of EstimatorResult.

**Raises**

- [**TypeError**](https://docs.python.org/3/library/exceptions.html#TypeError) – Invalid argument type given.
- [**ValueError**](https://docs.python.org/3/library/exceptions.html#ValueError) – Invalid argument values given.

**Return type**

T

### set\_options

`set_options(**fields)`

[GitHub](https://github.com/Qiskit/qiskit/tree/stable/1.3/qiskit/primitives/base/base_primitive.py#L39-L45)

Set options values for the estimator.

**Parameters**

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