Webinar series on

Light-Matter Interaction

This series of webinars aims at discussing exciting new concepts and developments related to light-matter interaction. They also offer an occasion to interact with early-career researchers and discuss stimulating new ideas in the field of photophysics and photochemistry – compensating somehow for the discussions one may have during a workshop. 

If you are interested in joining our webinars, please contact Basile directly.

24 September 2020 – 4.30pm (BST)

Mixed Quantum-Classical Dynamics in Cavity Quantum Electrodynamics

by Dr. Norah Hoffmann (Columbia University)

Chemical reactions under the influence of light play a paramount role in everyday life, from fundamental biological processes such as photosynthesis, vision, and DNA radiation-damage, to sustainable energy applications such as solar cells. Thus, controlling or optimizing the underlying chemical processes is of great interest. Recently, experimental developments in cavity Quantum Electrodynamics (QED) have opened up new possibilities of modifying and controlling chemical reactions by taking advantage of the strong light-matter interaction that arises when matter is confined in cavities. In such experiments the quantized nature of light becomes important and can profoundly change the chemical landscape. However, investigating these new developments from the theoretical point of view presents a challenging and especially high-dimensional problem, i.e. many molecules (electrons and nuclei) interacting with quantized light fields (many photon modes). Therefore, the theoretical simulation and prediction of realistic cavity QED experiments is by far not a trivial task and requires accurate and computationally efficient approximations.
To this end, we investigated and benchmarked extensions of mixed-quantum classical trajectory methods and time-dependent potential energy surfaces, both traditionally introduced for electron-nuclear problems, to the photonic degrees of freedom. In this talk I will discuss, how Wigner-sampling schemes for photons enable us to introduce quantized light-fields and multi-photon-mode treatments to quantum dynamics simulations in a computational efficient way, by properly accounting for the quantum statistics of the vacuum field while using classical/semi-classical trajectories to describe the time-evolution. Additionally, I will give an overview of our latest work on extending the exact-factorization approach to the photonic degrees of freedom, in order to set a starting point for the development of new mixed-quantum classical approaches within strongly coupled light-matter systems.

A schematic of a mixed quantum-classical approach for photons, the cavity Multi-Trajectory Ehrenfest (cMTE) algorithm (left). A molecule coupled to many photon modes (right) and the corresponding nuclear dynamics when coupling to a single photon mode (a) vs. the effect of coupling to many cavity photon modes, where spBO denotes the self-polarization modified Born-Oppenheimer-surfaces.