Dresden 2011 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 23: Poster 2: Intersectional Session

Q 23.25: Poster

Tuesday, March 15, 2011, 18:00–21:00, P1

A Bose-Einstein Condensate as Quantum Memory for Optical Polarisation Qubits — •Christoph Vo, Matthias Lettner, Martin Mücke, Stefan Riedl, Carolin Hahn, Simon Baur, Jörg Bochmann, Stephan Ritter, Stephan Dürr, and Gerhard Rempe — Max-Planck-Institute of Quantum Optics, Hans-Kopfermann-Str. 1, 85748 Garching

We present the experimental characterization of a quantum memory for optical polarisation qubits using electromagnetically induced transparency (EIT) in a Bose-Einstein condensate of ⁸⁷Rb atoms. Our system operates 70 MHz detuned from the D₁-line in a moderately-detuned Raman regime rather than the on-resonance EIT regime. Photonic polarisation qubits are mapped onto Zeeman qubits in the atomic system. Using classical light pulses, we performed a full quantum process tomography to determine the Müller matrix of the system.

To demonstrate the performance of our memory in the quantum regime, we stored a single photon of a polarisation-entangled Einstein-Podolsky-Rosen pair. After retrieving the stored photon from the memory we performed a quantum state tomography to determine the density matrix of the bi-partite system and found close resemblance with the original state. The fidelity of the retrieved state with respect to the maximally-entangled |Ψ⁻⟩ Bell state is found to be well above the classical limit of 0.5, showing the memory’s suitability as building block of a quantum repeater for long-distance quantum communication.