Open Quantum Dynamics Lab

Quantum mechanics and statistical physics describe basic processes in the domain of biophysics and light harvesting: in photosynthesis electronic states are excited by photon absorption and subsequently transfer part of the energy to molecular vibrations. This destroys the initially coherent state and enables charge transfer and charge separation. Similar processes are relevant for quantum information processing. There, the molecules are replaced by superconducting circuits, whose entanglement is counteracted by the environment. The computation of the exact dynamics in open quantum systems is a tedious task for classical computers and fully supported by only few software packages. Common approximations (no entanglement between quantum system and environment, neglect of temporal correlations, ...) do not allow one to capture the details of the dynamics and fail to accurately describe and predict the behaviour. The open quantum dynamics toolbox builds upon a collection of scalable and highly performant software publicly available at http://openquantumlab.de . This software was developed in our previous projects for the simulation of the coherent dynamics, computations of time and frequency resolved spectra, and time- dependent quantum operations. Our current focus is to provide an improved user experience to increase the user base across different scientific domains. We will ease the installation of the tools to lower the barrier for user contributions and to support a sustainable development and future extension. We update the provided documentation with tutorials and blog entries. The source code is partly generated from computer algebra systems and allows users to simply enhance the program and test new algorithms, also from new scientific domains. A python user interface simplifies the input of parameters and shows an interactive visualization of the computed results. We envision that the tool provided by the open quantum dynamics toolbox serve as a reference library for reproducible and verifiable results of open quantum systems.

The Open Quantum Dynamics Lab has advanced the development and application of powerful simulation software for quantum systems in their natural environment. The focus is on molecular systems and quantum devices whose behavior cannot be considered in isolation: they constantly interact with their surroundings. These interactions influence, for example, how energy is transported within molecules, how long quantum effects persist, and which optical properties a material exhibits. Such processes are of great importance for understanding photosynthesis, developing new light-active materials, and advancing future quantum technologies. The software further developed within the project is based on the DM-HEOM program. It enables highly accurate computer simulations, but often requires large amounts of memory and long computation times. A major part of the project consisted of making these demanding calculations more accessible and reliable. To this end, a graphical user interface was developed in particular. It helps researchers correctly compile the extensive settings required for a simulation. This makes the software easier to use, reduces input errors, and improves the reproducibility and traceability of calculations. The software was also successfully used in several projects involving international collaboration at Johannes Kepler University Linz. The studies investigated light-harvesting molecular complexes of the kind found in photosynthetic organisms. These systems capture sunlight and transfer the absorbed energy onward. The calculations made it possible to compare simplified theoretical descriptions with highly accurate reference calculations. The results were published in peer-reviewed scientific journals. Another important contribution of the project is its exchange with the open-source software package QuTiP, which is used worldwide for simulations of quantum systems. Comparing independent software programs is a particularly effective means of quality assurance: differences in results may reveal errors or missing features. Through these comparisons, bug fixes and improvements were initiated and incorporated into the further development of QuTiP. The benefits of the project therefore also extend to the wider scientific community.