---
title: gamma (latest version)
description: API reference for qiskit_fermions.operators.gamma in the latest version of qiskit-fermions
source: https://quantum.cloud.ibm.com/docs/en/api/qiskit-fermions/operators-gamma
---

# gamma

`gamma(mode, is_prime)`

Create a majorana fermion.

## For a given mode `i`, two majorana fermions can be created:

- `gamma(i, False)` creates $\gamma = a_i^\dagger + a_i$
- `gamma(i, True)` creates $\gamma' = i(a_i^\dagger - a_i)$

The argument order is `(mode, is_prime)` to reflect the natural interpretation of majorana operators: first specify the mode, then the variant. Unlike fermionic operators – where the distinction between creation and annihilation is fundamental – the two majorana variants are more symmetric and conceptually less different.

This mirrors the normal-ordering convention for majoranas, where operators are sorted first by mode and then by variant. For example, a normally ordered string like `((1, True), (0, False), (0, True)` is more readable and intuitive than `((True, 1), (False, 0), (True, 0)`.

**Parameters**

- **mode** ([*int*](https://docs.python.org/3/library/functions.html#int)) – index of the fermionic mode.
- **is\_prime** ([*bool*](https://docs.python.org/3/library/functions.html#bool)) – whether to create $\gamma$ (False) or $\gamma'$ (True).

**Returns**

A `MajoranaAction` object, which is essentially the flat index `2*mode+int(is_prime)`.

**Return type**

[int](https://docs.python.org/3/library/functions.html#int)