EstimatorV2

class EstimatorV2(mode=None, options=None)

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 RealAmplitudes
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 = RealAmplitudes(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(theta1)|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[BackendV1, 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

options

version

Methods

backend

run