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---
title: save_expectation_value_variance (v0.31)
description: API reference for qiskit.providers.aer.library.save_expectation_value_variance in qiskit v0.31
in_page_toc_min_heading_level: 1
python_api_type: function
python_api_name: qiskit.providers.aer.library.save_expectation_value_variance
---
<span id="qiskit-providers-aer-library-save-expectation-value-variance" />
# qiskit.providers.aer.library.save\_expectation\_value\_variance
<Function id="qiskit.providers.aer.library.save_expectation_value_variance" isDedicatedPage={true} github="https://github.com/qiskit/qiskit-aer/tree/stable/0.9/qiskit/providers/aer/library/save_instructions/save_expectation_value.py" signature="save_expectation_value_variance(self, operator, qubits, label='expectation_value_variance', unnormalized=False, pershot=False, conditional=False)">
Save the expectation value of a Hermitian operator.
**Parameters**
* **operator** ([*Pauli*](qiskit.quantum_info.Pauli "qiskit.quantum_info.Pauli") *or*[*SparsePauliOp*](qiskit.quantum_info.SparsePauliOp "qiskit.quantum_info.SparsePauliOp") *or*[*Operator*](qiskit.quantum_info.Operator "qiskit.quantum_info.Operator")) a Hermitian operator.
* **qubits** (*list*) circuit qubits to apply instruction.
* **label** (*str*) the key for retrieving saved data from results.
* **unnormalized** (*bool*) If True return save the unnormalized accumulated or conditional accumulated expectation value and variance over all shot \[Default: False].
* **pershot** (*bool*) if True save a list of expectation values and variances for each shot of the simulation rather than the average over all shots \[Default: False].
* **conditional** (*bool*) if True save the data conditional on the current classical register values \[Default: False].
**Returns**
with attached instruction.
**Return type**
[QuantumCircuit](qiskit.circuit.QuantumCircuit "qiskit.circuit.QuantumCircuit")
**Raises**
**ExtensionError** if the input operator is invalid or not Hermitian.
<Admonition title="Note" type="note">
This method appends a [`SaveExpectationValueVariance`](qiskit.providers.aer.library.SaveExpectationValueVariance "qiskit.providers.aer.library.SaveExpectationValueVariance") instruction to the quantum circuit.
</Admonition>
</Function>