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PRODID:UW-Madison-Physics-Events
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UID:UW-Physics-Event-2032
DTSTART:20110121T220000Z
DURATION:PT1H0M0S
DTSTAMP:20260420T145852Z
LAST-MODIFIED:20101202T144927Z
LOCATION:2241 Chamberlin Hall (coffee at 3:30 pm)
SUMMARY:The role of quantum coherence in photosynthetic energy transfe
 r\, Physics Department Colloquium\, Alán Aspuru-Guzik\, Harvard Unive
 rsity
DESCRIPTION:Long-lived electronic coherences in various photosynthetic
  complexes at cryogenic and room temperature have generated vigorous e
 fforts both in theory and experiment to understand their origins and e
 xplore their potential role to biological function. The ultrafast sign
 als resulting from the experiments that show evidence for these cohere
 nces result from many contributions to the molecular polarization. Qua
 ntum process tomography (QPT) is a technique whose goal is that of obt
 aining the time-evolution of all the density matrix elements based on 
 a designed set of experiments with different preparation and measureme
 nts. The QPT procedure was conceived in the context of quantum informa
 tion processing to characterize and understand general quantum evoluti
 on of controllable quantum systems\, for example while carrying out Qu
 antum computational tasks. We introduce our QPT method for ultrafast e
 xperiments\, and as an illustrative example\, apply it to a simulation
  of a two-chromophore subsystem of the FMO photosynthetic complex\, wh
 ich was recently shown to have long-lived quantum coherences. Our FMO 
 model is constructed using an atomistic approach to extract relevant p
 arameters for the simulation of photosynthetic complexes that consists
  of a quantum mechanics/molecular mechanics approach combined with mol
 ecular dynamics and the use of state-of-the-art quantum master equatio
 n approaches. We provide a set of methods that allow for quantifying t
 he role of quantum coherence\, dephasing\, relaxation and other elemen
 tary processes in energy transfer efficiency in photosynthetic complex
 es\, based on the information obtained from the atomistic simulations\
 , or\, using QPT\, directly from the experiment. The possible presence
  or absence of effects due to correlated protein motion is discussed. 
 The role of non-Markovianity will be discussed. The ultimate goal of t
 he combination of this diverse set of methodologies is to provide a re
 liable way of quantifying the role of long-lived quantum coherences an
 d obtain atomistic insight of their causes. 
URL:https://www.physics.wisc.edu/events/?id=2032
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