Hey all,
Former group member Ivan Kassal (
http://www.ivankassal.com/) will be
visiting next week on Monday, Tuesday, and Wednesday. He will be giving us
a special group meeting on Wednesday the 20th from 11 - 12 in M217. His
abstract is below. He is free to meet with group members on the afternoon
of the 18th, anytime on the 19th, and has some time before and after his
talk on the 20th. Please let me know if and when you would like to meet
with him!
Sam
Abstract:
Photosynthetic organisms harvest light using large antenna complexes with
many chlorophyll molecules. Because experiments have shown that energy
transport through antenna complexes—and onward to a reaction centre—is
partially coherent, it has become necessary to treat these processes using
computationally expensive techniques from the theory of open quantum
systems. This often requires integrating complicated non-Markovian
dynamics, followed by averaging over a potentially large ensemble.
However, many of the quantum effects observed in photosynthetic complexes
are artefacts of the ultrafast laser excitation and are not relevant in
incoherent natural illumination. As a consequence, the complete description
of energy transport in incoherent light is dramatically simplified. In
particular, the often-dubious Markov approximation becomes exact, while the
rotating-wave approximation—often unjustified but nevertheless imposed to
avoid certain pathologies—becomes unnecessary. With these simplifications,
computing any relevant observable is reduced to a problem of linear
algebra. This allows a rapid analysis of hypothetical scenarios to
determine whether natural light-harvesting architectures are already
optimal or whether they could be improved.
Although some quantum effects are not important for natural light
harvesting, others are nevertheless pronounced. I will provide several
examples of light-harvesting complexes where the underlying coherence
enhances the transport efficiency and use the techniques described above to
show that although some are close to being optimal, others are not.