MPS/CHE-EPSRC: Molecular vibrations and the evolution of entanglement in photochemical dynamics

Researchers from the University of Texas at Austin along with collaborators at the University of Cambridge in the United Kingdom are exploring how molecular vibrations affect entanglement dynamics in photochemical reactions. The real-time evolution of entanglement in electronic dynamics is indicative of the ability of a system to convert light into chemical work. While vibrations are ubiquitous, it remains unclear whether they are universally detrimental as has been thought conventionally, or whether certain vibrations can in fact promote entanglement between electronic states. The research team will use a combination of tensor network-based quantum dynamics simulations and ultrafast spectroscopy adapted to extract entanglement witnesses and thus clarify the role of molecular vibrations on real-time entanglement dynamics. Their discoveries could reveal strategies to use molecular vibrations as a means of steering entanglement dynamics, and hence photochemical reactions, towards desired pathways. The project will cement connections between quantum information science and chemistry, while training early-career researchers who are technically fluent in these areas. This award is made under the NSF-UKRI lead agency opportunity. Quantum entanglement between molecular electronic states quantifies non-classical correlations that determine photochemical reaction pathways. However, entanglement is often considered too fragile to affect photochemistry, due to its decay via coupling to molecular vibrations. Within this project, the team will develop a joint theoretical-experimental framework to track entanglement dynamics in real time, and to identify how vibrations affect these dynamics. The goal is to identify whether entanglement survives for timescales relevant to photochemistry, and to explore the possibility of vibrational control of entanglement. The photochemical process of singlet exciton fission, which generates entangled triplet pairs, will serve as a model system for entanglement dynamics in photochemistry. Entanglement witnesses, such as the Quantum Fisher Information, will be treated as the primary time-resolved observables. The team will construct molecular Hamiltonians using first-principles calculations and simulate their dynamics using tensor network methods that will allow them to quantify entanglement in real time. Experimentally, recently developed spectroscopic techniques will be adapted to track the Quantum Fisher Information in real time, combining this with the application of selective vibrational displacements. This integrated approach will allow for following entanglement in real time, quantifying how specific vibrations affect its dynamics, and identifying the potential for vibrational control of entanglement. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.