# CVaRMeasurement¶

class CVaRMeasurement(primitive=None, alpha=1.0, coeff=1.0)[ソース]

ベースクラス: qiskit.opflow.state_fns.operator_state_fn.OperatorStateFn

A specialized measurement class to compute CVaR expectation values.

See https://arxiv.org/pdf/1907.04769.pdf for further details.

Used in CVaRExpectation, see there for more details.

パラメータ
• primitive (Optional[OperatorBase]) – The OperatorBase which defines the diagonal operator measurement.

• coeff (Union[complex, ParameterExpression]) – A coefficient by which to multiply the state function

• alpha (float) – A real-valued parameter between 0 and 1 which specifies the fraction of observed samples to include when computing the objective value. alpha = 1 corresponds to a standard observable expectation value. alpha = 0 corresponds to only using the single sample with the lowest energy. alpha = 0.5 corresponds to ranking each observation by lowest energy and using the best

• ValueError – TODO remove that this raises an error

• ValueError – If alpha is not in [0, 1].

• OpflowError – If the primitive is not diagonal.

Methods Defined Here

 add Return Operator addition of self and other, overloaded by +. adjoint The adjoint of a CVaRMeasurement is not defined. compute_cvar Given the energies of each sampled measurement outcome (H_i) as well as the sampling probability of each measurement outcome (p_i, we can compute the CVaR. eval Given the energies of each sampled measurement outcome (H_i) as well as the sampling probability of each measurement outcome (p_i, we can compute the CVaR as H_j + 1/α*(sum_i

Attributes

INDENTATION = ' '
alpha
A real-valued parameter between 0 and 1 which specifies the

fraction of observed samples to include when computing the objective value. alpha = 1 corresponds to a standard observable expectation value. alpha = 0 corresponds to only using the single sample with the lowest energy. alpha = 0.5 corresponds to ranking each observation by lowest energy and using the best half.

float

The parameter alpha which was given at initialization

coeff

A coefficient by which the state function is multiplied.

Union[complex, ParameterExpression]

instance_id

Return the unique instance id.

int

is_measurement

Whether the StateFn object is a measurement Operator.

bool

num_qubits

int

parameters
primitive: qiskit.opflow.operator_base.OperatorBase

The primitive which defines the behavior of the underlying State function.

settings

Return settings.

Dict