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Date: Tuesday May 17, 2011
Time: 18:00
Place: ETH Science City, HPF G 6
Host: Andreas Wallraff
High-speed optical quantum memories
Klaus Reim
Abstract:
In a globalised
world with ever-increasing, intercontinental information exchange, there is growing
demand for secure communication technology, such as could be provided by photonic
quantum communications networks. Currently, the biggest challenge for such networks
is distance. Over short distances, photons, interacting only weakly with their environment,
easily and reliably carry quantum information without much decoherence, but intercontinental
quantum communication will require quantum repeaters embedded in potentially isolated
locations, because photon loss rises otherwise exponentially with distance. In general,
these repeaters will require some sort of quantum memory, a coherent device where
single photons are reversibly coupled into and out of an atomic system, to be stored,
possibly processed and then redistributed. In order to be practically useful, this
will need to have sufficiently large bandwidth, high efficiency and long storage
time, with multimode capacity, and a low-enough noise level to enable operation
at the quantum level.
I am going to
talk about our ensemble-based, far off-resonant Raman approach to quantum memories,
describe how the interaction mechanism works and show how we store a single photon
level signal in the quantum memory and retrieve it at a controlled later point in
time. Furthermore, I am going to address de-phasing mechanisms for the stored spin-wave
excitation that limit storage times and discuss storage and retrieval of polarization-encoded
qubits.
Publications:
Reim, K. F. et al. Nature Photon. 4, 218-221 (2010)
Reim, K. F. et al. arXiv:1010.3975v1
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ETH Zurich
Dr. Ilona Blatter
NCCR QSIT Coordinator
Laboratory for Solid State Physics
HPF E 17
Schafmattstrasse 16
8093 Zurich