2021/10/25 by Robert L. Cook, Cook, Robert L., Liwen Ko +3 · 1 voice · 1 citation
Biochemistry, Genetics and Molecular Biology · Neuroscience · Physics and Astronomy · #Biological Physics (physics.bio-ph) #Chemical Physics (physics.chem-ph) #FOS: Physical sciences #Photoreceptor and optogenetics research #Photosynthetic Processes and Mechanisms #Quantum Physics (quant-ph) #Spectroscopy and Quantum Chemical Studies #physics.bio-ph #physics.chem-ph #quant-ph
paper · pdf · doi:10.48550/arxiv.2110.13811
openalex publication_date 2021/10/25 · arxiv published 2021/10/25 · openalex created_date 2022/07/25 · arxiv updated 2022/08/09 · openalex updated_date 2026/07/28
In this work we study the first step in photosynthesis for the limiting case of a single photon interacting with photosystem II (PSII). We model our system using quantum trajectory theory, which allows us to consider not only the average evolution, but also the conditional evolution of the system given individual realizations of idealized measurements of photons that have been absorbed and subsequently emitted as fluorescence. The quantum nature of the single photon input requires a fully quantum model of both the input and output light fields. We show that PSII coupled to the field via three collective ``bright states'', whose orientation and distribution correlate strongly with its natural geometry. Measurements of the transmitted beam strongly affects the system state, since a (null) detection of the outgoing photon confirms that the system must be in the electronic (excited) ground state. Using numerical and analytical calculations we show that observing the null result transforms a state with a low excited state population O( 10-5 ) to a state with nearly all population contained in the excited states. This is solely a property of the single photon input, as we confirm by comparing this behavior with that for excitation by a coherent state possessing an average of one photon, using a smaller five site ``pentamer'' system. We also examine the effect of a dissipative phononic environment on the conditional excited state dynamics. We show that the environment has a strong effect on the observed rates of fluorescence, which could act as a new photon-counting witness of excitonic coherence. The long time evolution of the phononic model predicts an experimentally consistent quantum efficiency of 92%.