A Universal Approach for Solving Real-World Problems Using Quantum Dynamics: Coherent States for Molecular Simulations (COSMOS)

Experiments using modern laser technologies and new light sources look at quantum systems undergoing dynamic change to understand molecular function and answer fundamental questions relevant to chemistry, materials and quantum technologies. Typical questions are: How can molecules be engineered for maximum efficiency during energy harvesting, UV protection or photocatalysis? What happens when strong and rapidly changing laser fields act on electrons in atoms and molecules? How fast do qubits lose information due to interactions with the environment? Will an array of interacting qubits in future quantum computers remain stable over long time-scales?

Interpreting time-resolved experiments that aim to answer these questions requires Quantum Dynamics (QD) simulations, the theory of quantum motion. QD is on the cusp of being able to make quantitative predictions about large molecular systems, solving the time-dependent Schrödinger equation in a way that will help unravel the complicated signals from state-of-the-art experiments and provide mechanistic details of quantum processes. However, important methodological challenges remain, such as computational expense and accurate prediction of experimental observables, requiring a concerted team-effort. Addressing these will greatly benefit the wider experimental and computational QD communities.

In this programme grant we will develop transformative new QD simulation strategies that will uniquely deliver impact and insight for real-world applications across a range of technological and biological domains. The key to our vision is the development, dissemination, and wide adaptation of powerful new universal software for QD simulations, building on our collective work on QD methods exploiting trajectory-guided basis functions. Present capability is, however, held back by the typically fragmented approach to academic software development. This lack of unification makes it difficult to use ideas from one group to improve the methods of another group, and even the simple comparison of QD simulation methods is non-trivial. Here, we will combine a wide range of existing methods into a unified code suitable for use by both computational and experimental researchers to model fundamental photo-excited molecular behaviour and interpret state-of-the-art experiments. Importantly we will develop and implement new mathematical and numerical ideas within this software suite, with the explicit objective of pushing the system-size and time-scale limits beyond what is currently accessible within "standard" QD simulations. Our unified code will lead to powerful and reliable QD methods, simultaneously enabling easy adoption by non-specialists; for the first time, scientists developing and using QD simulations will be able to access, develop and deploy a common software framework, removing many of the inter- and intra-community barriers that exist within the current niche software set-ups across the QD domain.

The transformative impact of method development and code integration is powerfully illustrated by electronic structure and classical molecular dynamics packages, used routinely by thousands of researchers around the world and recognised by several Nobel Prizes in the last few decades. Our programme grant aims to deliver a similar step-change by improving accessibility for QD simulations. Success in our programme grant would be the demonstrated increase in adoption of advanced QD simulations across a broad range of end-user communities (e.g. spectroscopy, materials scientists, molecular designers). Furthermore, by supporting a large yet integrated cohort of early-career researchers, this programme grant will provide an enormous acceleration to developments in QD, positioning the UK as a global leader in this domain as we move from the era of classical computation and simulation into the quantum era of the coming decades.