Berlin 2014 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 28: Quantum information: Atoms and ions IV

Q 28.4: Talk

Tuesday, March 18, 2014, 14:45–15:00, UDL HS3038

A reversible quantum memory for OAM qubits — •Dominik Maxein, Adrien Nicolas, Lucile Veissier, Lambert Giner, Elisabeth Giacobino, and Julien Laurat — Laboratoire Kastler Brossel, Université Pierre et Marie Curie, École Normale Supérieure, and CNRS, 4 place Jussieu, 75252 Paris Cedex 05, France

Quantum communication and information processing with orbital angular momentum states of light (OAM states) promises a capacity increase by employing high-dimensional information encoding [G. Molina-Terriza et al., Nature Phys. 3, 305 (2007)]. We report on the first implementation and characterization of a quantum memory for quantum bits encoded in this optical degree of freedom. This is an important step towards future quantum networks [H.J. Kimble, Nature 453, 1023 (2008)] exploiting the potential of OAM of photons for quantum information applications.

Specifically, we prepare weak light pulses in Laguerre-Gaussian modes with p=0 and l=±1 and superpositions thereof. They are stored in an ensemble of cold Cs atoms using dynamical electromagnetically induced transparency. A complete tomography of the states retrieved from the memory is performed using a setup of forked holograms, an interferometer and single-photon counters, yielding fidelities above 90%. Comparing the obtained fidelities with the classically possible limit [H.P. Specht et al., Nature 473, 190 (2011)] for a varying mean photon number per pulse (between 0.3 and 50), we show that our system is indeed a quantum memory for OAM encoded qubits [A. Nicolas et al., Nature Photon. (accepted), arXiv 1308.0238 (2013)].