qrunch.quantum.estimators.backend_estimator

Module with implementations of estimator.

Classes

Class for estimating observables.

class BackendEstimator

Bases: Estimator

Class for estimating observables.

__init__(sampler: Sampler, grouper: MeasurementGrouper | None = None, error_mitigator: EstimatorErrorMitigator | None = None, measurement_cache: MeasurementCache | None = None) → None

Initialize estimator on the specified backend.

Parameters:

sampler (Sampler) – The sampler used for the calculations.
grouper (MeasurementGrouper | None) – How to group the terms in the observable.
error_mitigator (EstimatorErrorMitigator | None) – Error mitigator to be used for encoding the observable or circuit more error resistantly.
measurement_cache (MeasurementCache | None) – Cache to use for storing and reusing measurements and expectation values.

Return type:

None

clear_cache() → None

Clear the measurement cache.

get_sampler() → Sampler

Get the sampler used in the estimator.

has_spin_particle_conservation() → bool

Return True, if the estimator is set to use spin particle conservation.

has_total_particle_conservation() → bool

Return True, if the estimator is set to use total particle conservation.

Estimate the value of the observables using the circuit state.

For each observable the following will be calculated: <circuit|observable|circuit>.

Parameters:

observables (Sequence[int | float | complex | Expression[PauliOperators]] | int | float | complex | Expression[PauliOperators] | Sequence[HermitianPauliSum] | HermitianPauliSum) – Observable(s) to be estimated.
circuits (Circuit | Sequence[Circuit]) – States to make estimation from.
shots (int | None) – number of shots or None if using a full state vector calculation.

Return type:

supports_shots_equals_none() → bool

Return whether the estimator supports shots = None.

The backend estimator support shots=None if the underlying sampler supports it.