# qiskit.algorithms.eval_observables

`eval_observables(quantum_instance, quantum_state, observables, expectation, threshold=1e-12)`

Pending deprecation: Accepts a list or a dictionary of operators and calculates their expectation values - means and standard deviations. They are calculated with respect to a quantum state provided. A user can optionally provide a threshold value which filters mean values falling below the threshold.

This function has been superseded by the `qiskit.algorithms.observables_evaluator.eval_observables()`

function. It will be deprecated in a future release and subsequently removed after that.

**Parameters**

**quantum_instance**(`Union`

[`QuantumInstance`

,`Backend`

]) – A quantum instance used for calculations.**quantum_state**(`Union`

[`Statevector`

,`QuantumCircuit`

,`OperatorBase`

]) – An unparametrized quantum circuit representing a quantum state that expectation values are computed against.**observables**(`Union`

[`List`

[`Optional`

[`OperatorBase`

]],`Dict`

[`str`

,`OperatorBase`

]]) – A list or a dictionary of operators whose expectation values are to be calculated.**expectation**(`ExpectationBase`

) – An instance of ExpectationBase which defines a method for calculating expectation values.**threshold**(`float`

) – A threshold value that defines which mean values should be neglected (helpful for ignoring numerical instabilities close to 0).

**Return type**

`Union`

[`List`

[`Optional`

[`Tuple`

[`complex`

, `complex`

]]], `Dict`

[`str`

, `Tuple`

[`complex`

, `complex`

]]]

**Returns**

A list or a dictionary of tuples (mean, standard deviation).

**Raises**

**ValueError** – If a `quantum_state`

with free parameters is provided.