Approximating quantum thermodynamic properties using DFT

TL;DR

This paper compares simple and hybrid density functional theory-based approximations for quantum thermodynamic properties, demonstrating their efficiency and accuracy in modeling driven many-body systems like Hubbard chains.

Contribution

It introduces and systematically evaluates computationally efficient DFT-based approximations for quantum thermodynamics in many-body systems, highlighting their advantages over traditional methods.

Findings

Hybrid approach improves accuracy for entropy calculations.

Good Kohn-Sham Hamiltonian approximates driving Hamiltonian effectively.

Approximations are computationally cheap and suitable for large systems.

Abstract

The fabrication, utilisation, and efficiency of quantum technologies rely on a good understanding of quantum thermodynamic properties. Many-body systems are often used as hardware for these quantum devices, but interactions between particles make the complexity of related calculations grow exponentially with the system size. Here we explore and systematically compare `simple' and `hybrid' approximations to the average work and entropy variation built on static density functional theory concepts. These approximations are computationally cheap and could be applied to large systems. We exemplify them considering driven one-dimensional Hubbard chains and show that, for `simple' approximations and low to medium temperatures, it pays to consider a good Kohn-Sham Hamiltonian to approximate the driving Hamiltonian. Our results confirm that a `hybrid' approach, requiring a very good approximation of the initial and, for the entropy, final states of the system, provides great improvements. This approach should be particularly efficient when many-body effects are not increased by the driving Hamiltonian.