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# CVaRMeasurement¶

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

Bases : `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.

Paramètres
• 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

Lève
• 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.

Type renvoyé

`float`

Renvoie

The parameter alpha which was given at initialization

coeff

A coefficient by which the state function is multiplied.

Type renvoyé

`Union`[`complex`, `ParameterExpression`]

instance_id

Return the unique instance id.

Type renvoyé

`int`

is_measurement

Whether the StateFn object is a measurement Operator.

Type renvoyé

`bool`

num_qubits
Type renvoyé

`int`

parameters
primitive: OperatorBase

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

settings

Return settings.

Type renvoyé

`Dict`