# 2.1. Introduction¶

Tkwant is a Python package for the simulation of quantum nanoelectronics devices on which external time-dependent perturbations are applied. Tkwant is an extension of the Kwant package and can handle the same types of systems: discrete tight-binding like models that consist of an arbitrary central region connected to semi-infinite electrodes, also called leads. For such systems, tkwant provides algorithms to simulate the time-evolution of manybody expectation values, as e.g. densities and currents.

**Input**: A tight-binding Hamiltonian of generic form

as well as the chemical potential \(\mu\) and the temperature \(T\) in each lead.

**Output**: Time-dependent manybody expectation values, such as
the electron density \(n_i(t) = \langle \hat{c}^\dagger_i \hat{c}_i \rangle\)
an currents
\(j_i(t) = i[\langle \hat{c}^\dagger_i \hat{c}_{i+1} \rangle - \langle \hat{c}^\dagger_{i+1} \hat{c}_{i} \rangle]\).
We refer to Tkwant’s main paper Ref. [1] for the technical background.

## 2.1.1. References¶

[1] T. Kloss, J. Weston, B. Gaury, B. Rossignol, C. Groth and X. Waintal, Tkwant: a software package for time-dependent quantum transport, arXiv:2009.03132 [cond-mat.mes-hall].