on 14-11-2014
Jean-Michel Raimond, École Normale Supérieure
14/11/2014, 14:00
Room P9, Mathematics Building, IST
Quantum non-demolition information on the number of microwave photons stored in a superconducting cavity can be obtained by sending trough the mode circular Rydberg atoms, interacting dispersively with the field. This information can be used to reveal the quantum jumps of light. We will describe an optimal use of this information, based on the past quantum state formalism. Photon number measurement can also be used to stabilize a non-classical photon number state against decoherence, in a quantum feedback process operating in the steady state. Finally, the principle of quantum feedback can be applied to an improved adaptive QND measurement of the photon number. We shall report on these recent experiments and on the perspectives they open for non-classical state manipulations.
Quantum Computation and Information Seminar
http://math.tecnico.ulisboa.pt/seminars/qci/?action=next
Support: Phys-Info (IT), SQIG (IT), CFIF and CAMGSD, with support from FCT, FEDER and EU FP7, namely via the Doctoral Programme in the Physics and Mathematics of Information (DP-PMI), and projects PEst-OE/EEI/LA0008/2013, CQVibes, Landauer (318287) and PAPETS (323901).
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on 07-11-2014
Niek van Hulst, ICFO – The Institute of Photonic Sciences
07/11/2014, 14:00
Room P9, Mathematics Building, IST
I will address the role of quantum effects in photosynthesis. Exploring individual pigment-protein complexes (LH2) of a purple bacterium with coherent fs pulses it is observed that ultrafast quantum coherent energy transfer occurs under physiological conditions. Surprisingly quantum coherences between electronically coupled energy eigen-states persist at least 400 fs, and distinct, time-varying energy transfer pathways can be identified in each complex. Interestingly the single molecule approach allows to track coherent phase jumps between different pathways, which suggest that long-lived quantum coherence renders energy transfer robust in the presence of disorder.
The photosynthetic antenna complexes are efficient in energy transfer, yet such complexes are not designed to emit light and thus hard to observe at the level of individual units. We have developed nanofabrication methods to couple single pigment complexes resonantly to a gold nanoantenna. This way the fluorescence decay speeds up from nanosecond to picosecond timescale, the quantum efficiency is enhanced and up to 1000 times more emission is collected. Using the bright photon emission, we revealed that the bacterial LH2 complex with 27 bacteriochlorophylls coordinated in two rings of chromophores shows photon anti-bunching at ambient conditions, i.e. a bacterial complex acting as a non-classical single-photon emitter.
Quantum Computation and Information Seminar
http://math.tecnico.ulisboa.pt/seminars/qci/?action=next
Support: Phys-Info (IT), SQIG (IT), CFIF and CAMGSD, with support from FCT, FEDER and EU FP7, namely via the Doctoral Programme in the Physics and Mathematics of Information (DP-PMI), and projects PEst-OE/EEI/LA0008/2013, CQVibes, Landauer (318287) and PAPETS (323901).
More Information..