---
title: groups_have_uniform_coeffs (latest version)
description: API reference for qiskit_fermions.operators.terms.groups_have_uniform_coeffs in the latest version of qiskit-fermions
source: https://eu-de.quantum.cloud.ibm.com/docs/en/api/qiskit-fermions/operators-terms-groups-have-uniform-coeffs
---

# groups\_have\_uniform\_coeffs

`groups_have_uniform_coeffs(op, *, atol=1e-08, abs=True)`

Returns, for each group, whether all of its coefficients are numerically equal.

With `abs` (the default), the coefficient *magnitudes* are compared, which is the assumption that [`group_coeff_means()`](/docs/api/qiskit-fermions/operators-terms-group-coeff-means "qiskit_fermions.operators.terms.group_coeff_means") makes when it averages `abs(coeff)`. Without it, the coefficients must match exactly. Note that a Hermitian group may legitimately fail the stricter form, since a conjugate pair with complex coefficients has equal magnitudes but unequal coefficients. If the operator tracks no groups, this returns `None`.

An empty or single-term group is trivially uniform.

> **Note**
>
> This is *not* a weaker form of [`groups_are_hermitian()`](/docs/api/qiskit-fermions/operators-terms-groups-are-hermitian "qiskit_fermions.operators.terms.groups_are_hermitian"): neither implies the other. Uniform coefficients do not make a group Hermitian, and a Hermitian group can mix magnitudes.

```pycon
>>> from qiskit_fermions.operators import FermionOperator
>>> from qiskit_fermions.operators.terms.grouping import groups_have_uniform_coeffs
>>> op = FermionOperator.from_dict(
...     {
...         ((True, 0), (False, 1)): 1.0j,
...         ((True, 1), (False, 0)): -1.0j,
...     }
... )
>>> op.groups = [0, 0]
>>> groups_have_uniform_coeffs(op)  # equal magnitudes
[True]
>>> groups_have_uniform_coeffs(op, abs=False)  # but not equal coefficients
[False]
```

**Parameters**

- **op** – the operator whose groups to check.
- **atol** – The numerical accuracy upto which coefficients are considered equal. This value defaults to `1e-8`.
- **abs** – Whether to compare coefficient magnitudes rather than the coefficients themselves. This value defaults to `True`.

**Returns**

One flag per group index, or `None` if the operator tracks no groups.

**Raises**

[**TypeError**](https://docs.python.org/3/builtins/exceptions.html#TypeError) – if `op` is not a supported operator type (see [`OperatorTrait`](/docs/api/qiskit-fermions/operators-operator-trait "qiskit_fermions.operators.OperatorTrait")).