# Ab initio relaxation times and time-dependent Hamiltonians within the steepest-entropy-ascent quantum thermodynamic framework

## TL;DR

This paper extends the steepest-entropy-ascent quantum thermodynamics framework to time-dependent Hamiltonians, providing an ab initio expression for relaxation times and addressing fundamental quantum thermodynamic questions.

## Contribution

It introduces a generalized SEAQT framework for all quantum systems with time-dependent Hamiltonians and derives a physically relevant expression for intra-relaxation time.

## Key findings

- Derived a universal expression for relaxation time applicable to all Hamiltonians.
- Resolved the issue of defining process-dependent work and heat in quantum thermodynamics.
- Enhanced the robustness of the SEAQT framework at the fundamental level.

## Abstract

Quantum systems driven by time-dependent Hamiltonians are considered here within the framework of steepest-entropy-ascent quantum thermodynamics (SEAQT) and used to study the thermodynamic characteristics of such systems. In doing so, a generalization of the SEAQT framework valid for all such systems is provided, leading to the development of an ab initio physically relevant expression for the intra-relaxation time, an important element of this framework and one that had as of yet not been uniquely determined as an integral part of the theory. The resulting expression for the relaxation time is valid as well for time-independent Hamiltonians as a special case and makes the description provided by the SEAQT framework more robust at the fundamental level. In addition, the SEAQT framework is used to help resolve a fundamental issue of thermodynamics in the quantum domain, namely, that concerning the unique definition of process-dependent work and heat functions. The developments presented lead to the conclusion that this framework is not just an alternative approach to thermodynamics in the quantum domain but instead one that uniquely sheds new light on various fundamental but as of yet not completely resolved questions of thermodynamics.