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MatrixExpectation

qiskit.opflow.expectations.MatrixExpectation

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Bases: ExpectationBase

An Expectation converter which converts Operator measurements to be matrix-based so they can be evaluated by matrix multiplication.

Deprecated since version 0.24.0

The class qiskit.opflow.expectations.matrix_expectation.MatrixExpectation is deprecated as of qiskit-terra 0.24.0. It will be removed in the Qiskit 1.0 release. For code migration guidelines, visit https://qisk.it/opflow_migration(opens in a new tab).


Methods

compute_variance

compute_variance(exp_op)

Compute the variance of the expectation estimator. Because this expectation works by matrix multiplication, the estimation is exact and the variance is always 0, but we need to return those values in a way which matches the Operator’s structure.

Parameters

exp_op (OperatorBase) – The full expectation value Operator.

Returns

The variances or lists thereof (if exp_op contains ListOps) of the expectation value estimation, equal to 0.

Return type

list(opens in a new tab) | float(opens in a new tab)

convert

convert(operator)

Accept an Operator and return a new Operator with the Pauli measurements replaced by Matrix based measurements.

Parameters

operator (OperatorBase) – The operator to convert.

Returns

The converted operator.

Return type

OperatorBase

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