Hannover 2013 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 32: Quantum information: Atoms and ions III

Q 32.7: Talk

Tuesday, March 19, 2013, 15:45–16:00, A 310

A reversible optical memory for twisted photons — •Dominik Maxein¹, Lucile Veissier¹, Adrien Nicolas¹, Lambert Giner¹, Alexandra S. Sheremet², Elisabeth Giacobino¹, and Julien Laurat¹ — ¹Laboratoire Kastler Brossel: Université Pierre et Marie Curie, École Normale Supérieure, and CNRS, 4 place Jussieu, 75252 Paris Cedex 05, France — ²Department of Theoretical Physics, State Polytechnic University, 195251, St.-Petersburg, Russia

“Twisted” single-photons carrying an orbital angular momentum (OAM) are promising information carriers in various quantum information protocols. They indeed offer the possibility of encoding and processing of information in high-dimensional Hilbert spaces, thus potentially allowing for higher efficiencies and enhanced information capacity. To use these states in quantum networks, light-matter interfaces play a crucial role, e.g. the reversible mapping of OAM into and out of atomic memories. Seminal experiments in this direction with “bright” OAM-carrying beams have already been performed [Pugatch et al, PRL 98, 203601 (’07) and Moretti et al, PRA 79, 023825 (’09)]

Here, we report on a multimode optical memory for the storage and retreival of the OAM of light, for the first time at the single-photon level. The light is mapped into and out of a cold atomic ensemble, using the dynamic electromagnetically-induced transparency protocol. We use very faint light pulses in Laguerre-Gaussian modes as signal and show that the handedness of their helical phase structure is preserved. This opens the possibility to the storage of qubits encoded as superpositions of orbital angular momentum states.