What is quatrex?#

The quatrex package is an ab initio quantum transport simulator developed in the computational nanoelectronics group at ETH Zürich. It is intended as the successor of the OMEN simulator, that was developed in the same group and has been used for many years in different research projects. Preliminary work on quatrex started in 2024, and the first public release was made in 2026.

Starting from a description of a nanosystem's geometry, its electronic structure (Hamiltonian and overlap matrix), and a set of relevant configuration parameters, quatrex computes transport properties, such as transmission and current spectra, non-equilibrium charge carrier densities, and current-voltage characteristics.

The underlying theory is the non-equilibrium Green's function (NEGF) formalism, which is a widely used framework for describing quantum transport in nanoscale systems¹. Besides a powerful method for simulating coherent transport based on the quantum transmitting boundary method (QTBM), quatrex implements NEGF with scattering effects, like screened Coulomb interactions at the level of the GW approximation² and electron-phonon interactions in a pseudo-scattering potential approach. You can find more details about the theoretical framework and the implemented methods in the methodology section of the user guide.

In terms of implementation and performance, we leverage Python's core CPU and GPU array frameworks, numpy and cupy, as well as associated frameworks and libraries, such as scipy, mpi4py, and numba. The quatrex codebase is designed to be extensible, portable, and highly performant. It has already shown excellent scaling on different supercomputers and even achieved sustained exascale performance on the Frontier supercomputer.³