qrunch.quantum.estimators.excitation_gate_estimator

Module with implementations of excitation gate estimator.

Classes

ExcitationGateEstimator

Class for estimating observables of spin particle preserving "excitation-gate-circuits".

class ExcitationGateEstimator

Bases: Estimator

Class for estimating observables of spin particle preserving “excitation-gate-circuits”.

An “excitation-gate-circuit” means a circuit consisting of only:

• a number of X gates to begin with,

• single or double excitation gates for the remaining part of the circuit.

This class, in particular, is for the case where the number of qubits is even, and the number of excitations in the first and second half of the circuit is conserved separately. In particular, for a circuit with 2N qubits, all the single and double excitation gates have to preserve the number of 1’s in first N (and last N) qubits.

__init__(options: ExcitationGateSimulatorOptions, grouper: MeasurementGrouper | None = None, error_mitigator: EstimatorErrorMitigator | None = None) → None

Initialize estimator.

Parameters:

• options (ExcitationGateSimulatorOptions) – Options for the estimator.

• grouper (MeasurementGrouper | None) – Grouper to use when running with shots.

• error_mitigator (EstimatorErrorMitigator | None) – Error mitigator to be used for encoding the observable or circuit more error resistantly.

Return type:

None

clear_cache() → None

Clear the measurement cache.

Return type:

None

has_spin_particle_conservation() → bool

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

Return type:

bool

has_total_particle_conservation() → bool

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

Return type:

bool

run(observables: Sequence[int | float | complex | Expression[PauliOperators]] | int | float | complex | Expression[PauliOperators] | Sequence[HermitianPauliSum] | HermitianPauliSum, circuits: Circuit | Sequence[Circuit], shots: int | None) → ExpectationValue | list[ExpectationValue] | EstimatorResults

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:

ExpectationValue | list[ExpectationValue] | EstimatorResults

supports_shots_equals_none() → bool

Return whether the estimator supports shots = None.

The ExcitationGateEstimator does support shots=None

Return type:

bool