Decoherence of coherent electronic excited state in the reaction center of the photosynthetic purple bacterium Rhodobacter sphaeroides

TL;DR

This paper models the quantum decoherence of energy transfer in photosynthetic bacteria using a spin-boson model and QUAPI, successfully matching experimental observations of coherence decay.

Contribution

It introduces a non-Markovian decoherence model for photosynthetic energy transfer, integrating photon effects and environmental interactions with a quasi-adiabatic path integral approach.

Findings

The model accurately reproduces experimental decoherence data.

Photon-induced effects significantly influence energy level dynamics.

Non-Markovian effects are crucial for understanding coherence decay.

Abstract

In this paper, we present a theoretical description to the quantum coherence and decoherence phenomena of energy transfer in photosynthesis observed in a recent experiment [see Science 316, 1462 (2007)]. As a successive two-color laser pulses with selected frequencies cast on a sample of the photosynthetic purple bacterium Rb. sphaeroides two resonant excitations of electrons in chromophores can be generated. However, this effective two-level subsystem will interact with its protein environment and decoherence is inevitable. We describe this subsystem coupled with its environment as a dynamical spin-boson model. The non-Markovian decoherence dynamics is described using a quasi-adiabatic propagator path integral (QUAPI) approach. With the photon-induced effective time-dependent level splitting energy and level flip coupling coefficient between the two excited states and the environment-induced non-Markovian decoherence dynamics, our theoretical result is in good agreement with the experimental data.