VCQ Colloquium Talk,Events,News Monday, 26 June, VCQ Colloquium Talk by Birgitta Whaley

Monday, 26 June, VCQ Colloquium Talk by Birgitta Whaley

We are glad to present  

Birgitta Whaley

University of California, Berkeley

Monday, 26 June 2023 at 18:00

Freihaus Hörsaal 3 at TU Wien (Wiedner Hauptstraße 8, 1040 Vienna, 2. OG)

Probing Photosynthesis with Single Photons

Photosynthetic light harvesting of plants and bacteria in vivo is characterized by the remarkable capability of producing electron-hole pairs from absorbed photons with near unit quantum efficiency under ultra-weak illumination conditions. Much experimental and theoretical work using techniques of ultrafast laser spectroscopy has been devoted to analysis of the excited state energy transfer following photoexcitation, but characterization of the initial absorption event has proven elusive.  I shall describe a new generation of experimental and theoretical studies using quantum light sources that allow explicit study of the absorption of individual photons. These studies make use of a time-resolved photon counting quantum light spectroscopy (PCQLS) that is based on a heralded single photon source together with coincidence counting. The first experiments reveal a cycle of single photon absorption and single photon fluorescent emission that validates the microscopic interpretation of conventional bulk measurements of quantum efficiency. Associated theoretical studies employing stochastic quantum trajectories conditioned on detection of fluorescent photons reveal the spatio-temporal dynamics of excitations following absorption of single photons with maximal information content.  I shall show how these techniques allow a microscopic analysis of the role of excitonic quantum coherence and the influence of vibrational/phonon modes on this, together with a consistent evaluation of the quantum efficiency resulting from absorption of individual photons. Implications for further exploration of the spatio-temporal dynamics of photosynthesis with quantum light sources will be discussed.

Host: Markus Aspelmeyer (UNIVIE/IQOQI)

For further information and a Zoom link please visit:


18:00 – VCQ Student Talk by Caroline Jones on “Theory-independent randomness generation with spacetime symmetries”

18:15 – VCQ Colloquium talk by Prof. Regal

***After the talk drinks & snacks on the roof-top terrace (Freihaus, Tower A, 9. OG )***

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