---
title: reconstruct_t2_alpha_beta (latest version)
description: API reference for qiskit_fermions.linalg.reconstruct_t2_alpha_beta in the latest version of qiskit-fermions
source: https://eu-de.quantum.cloud.ibm.com/docs/en/api/qiskit-fermions/linalg-reconstruct-t-2-alpha-beta
---

# reconstruct\_t2\_alpha\_beta

`reconstruct_t2_alpha_beta(terms, norb, nocc_a, nocc_b)`

Reconstructs alpha-beta $t_2$ amplitudes from a double-factorized decomposition.

**Parameters**

- **terms** – the list of terms produced by [`double_factorized_t2_alpha_beta()`](/docs/api/qiskit-fermions/linalg-double-factorized-t-2-alpha-beta "qiskit_fermions.linalg.double_factorized_t2_alpha_beta"), each a 2-tuple of the `(aa, ab, bb)` diagonal Coulomb matrices and the `(alpha, beta)` orbital rotations.
- **norb** – the number of orbitals.
- **nocc\_a** – the number of alpha-occupied orbitals.
- **nocc\_b** – the number of beta-occupied orbitals.

**Returns**

The reconstructed alpha-beta $t_2$ amplitudes of shape `(nocc_a, nocc_b, nvrt_a, nvrt_b)`.