Uniform process tensor approach for the calculation of multi-time correlation functions of non-Markovian open systems
Abstract
The process tensor framework to open quantum systems provides the most general description of multi-time correlations in non-Markovian quantum dynamics. A compressed representation of a process tensor in terms of matrix product operators (MPO) can be used for numerically exact calculations of multi-time correlation functions in systems strongly coupled to a non-Markovian reservoir. We show here that the numerical scaling for computing multi-dimensional spectra can be significantly improved using a time-translation invariant MPO representation of the process tensor obtained from the uniform time-evolving matrix product operator (uniTEMPO) method. In particular, this approach provides a spectral representation of the non-Markovian dynamics that gives direct access to correlation functions in Fourier-space, avoiding explicit real-time evolution. We calculate linear and 2D electronic spectra for an example system and discuss the performance and numerical scaling of our simulations.
Keywords
Cite
@article{arxiv.2603.04970,
title = {Uniform process tensor approach for the calculation of multi-time correlation functions of non-Markovian open systems},
author = {Matteo Garbellini and Konrad Mickiewicz and Valentin Link and Alexander Eisfeld and Walter T. Strunz},
journal= {arXiv preprint arXiv:2603.04970},
year = {2026}
}