Quantum Light Spectroscopy

Photosynthetic complexes have near unit quantum efficiencies. To study these highly efficient systems and the fundamental properties of light-matter interactions, we are implementing a new single photon spectroscopic technique. Some questions to be investigated include: is a single photon absorbed whole i.e. as a "quantum jump" or are interactions with multiple photons necessary for an absorption event to take place? By studying single photon absorption statistics, we can generate a distribution of photons absorbed per fluorescence event wherein a high frequency of occurrence for low photons absorbed per fluorescence event would be seen as evidence of quantum jumps.

For quantum light spectroscopy (QLS) we generate entangled photons from a non-linear crystal via spontaneous parametric down conversion (SPDC).These photons have (1) entangled polarizations, (2) correlated times, and (3) anti-correlated frequencies. These properties allow us to use the entangled photon pairs in a heralded single photon set up, ensuring that we are only observing the system dynamics in response to interaction with a single photon, rather than the billions from a conventional laser set up. Collaboration with K. Birgitta Whaley at UC Berkeley.

Contact: Quanwei Li

Helpful Background Reading:

1. Single-photon absorption by single photosynthetic light-harvesting complexes. H.C.H Chan, O.E. Gamel, G.R. Fleming, and K.B. Whaley, J. Phys. B: At. Mol. Opt. Phys., 51 (2018).

2. Entangled Two-Photon Absorption Spectroscopy. F. Schlawin, K.E. Dorfman, and S. Mukamel, Acc. Chem. Res., 51 (2018).

3. Entangled Photon Excited Fluorescence in Organic Materials: An Ultrafast Coincidence Detector. O. Varnavski, B. Pinsky, and T.J. Goodson III, Phys. Chem. Lett., 8 (2017).

4. Measurement of the spectral properties of the two-photon state generated via type II spontaneous parametric downconversion. Y.-H. Kim, and W.P. Grice, Opt. Lett., 30 (2005).