EstimatorV2

class EstimatorV2(mode=None, options=None)[source]

Bases: BasePrimitiveV2[EstimatorOptions], Estimator, BaseEstimatorV2

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.

Following construction, an estimator is used by calling its run() method with a list of PUBs (Primitive Unified Blocs). Each PUB contains four values that, together, define a computation unit of work for the estimator to complete:

  • a single QuantumCircuit, possibly parametrized, whose final state we define as \(\psi(\theta)\),

  • one or more observables (specified as any ObservablesArrayLike, including Pauli, SparsePauliOp, str) that specify which expectation values to estimate, denoted \(H_j\), and

  • a collection parameter value sets to bind the circuit against, \(\theta_k\).

  • an optional target precision for expectation value estimates.

Here is an example of how the estimator is used.

from qiskit.circuit.library import real_amplitudes
from qiskit.quantum_info import SparsePauliOp
from qiskit.transpiler.preset_passmanagers import generate_preset_pass_manager
from qiskit_ibm_runtime import QiskitRuntimeService, EstimatorV2 as Estimator

service = QiskitRuntimeService()
backend = service.least_busy(operational=True, simulator=False)

psi = real_amplitudes(num_qubits=2, reps=2)
hamiltonian = SparsePauliOp.from_list([("II", 1), ("IZ", 2), ("XI", 3)])
theta = [0, 1, 1, 2, 3, 5]

pm = generate_preset_pass_manager(backend=backend, optimization_level=1)
isa_psi = pm.run(psi)
isa_observables = hamiltonian.apply_layout(isa_psi.layout)

estimator = Estimator(mode=backend)

# calculate [ <psi(theta)|hamiltonian|psi(theta)> ]
job = estimator.run([(isa_psi, isa_observables, [theta])])
pub_result = job.result()[0]
print(f"Expectation values: {pub_result.data.evs}")

Initializes the Estimator primitive.

Parameters:

  • mode (Optional[Union[BackendV2, Session, Batch, str]]) –

    The execution mode used to make the primitive query. It can be:

    • A Backend if you are using job mode.

    • A Session if you are using session execution mode.

    • A Batch if you are using batch execution mode.

    Refer to the Qiskit Runtime documentation. for more information about the Execution modes.

  • options (Optional[Union[Dict, EstimatorOptions]]) – Estimator options, see EstimatorOptions for detailed description.

Attributes

mode

Return the execution mode used by this primitive.

Returns:

Mode used by this primitive, or None if an execution mode is not used.

options

Return options

version = 2

Methods

backend()[source]

Return the backend the primitive query will be run on.

Return type:

BackendV2

run(pubs, *, precision=None)[source]

Submit a request to the estimator primitive.

Parameters:

  • pubs (Iterable[EstimatorPubLike]) – An iterable of pub-like (primitive unified bloc) objects, such as tuples (circuit, observables) or (circuit, observables, parameter_values).

  • precision (float | None) – The target precision for expectation value estimates of each run Estimator Pub that does not specify its own precision. If None the estimator’s default precision value will be used.

Returns:

Submitted job.

Raises:

ValueError – if precision value is not strictly greater than 0.

Return type:

RuntimeJobV2