Hannover 2010 – wissenschaftliches Programm

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Q: Fachverband Quantenoptik und Photonik

Q 30: Quantum Effects: QED II / Interference and Correlations III

Q 30.5: Vortrag

Mittwoch, 10. März 2010, 15:00–15:15, A 320

Towards the experimental realisation of an ideal quantum measurement — •Jürgen Volz, Roger Gehr, Guilhem Dubois, Jérôme Estève, and Jakob Reichel — Laboratoire Kastler-Brossel de l'ENS, 24 rue Lhomond, Paris, France

Error free qubit readout is one of the key ingredient to quantum information processing. In the case of atomic qubits, such as ions or neutral atoms, the most effcient methods rely on measuring the response of the qubit to an optical excitation. Using resonant light, as in the shelving technique, or far off resonance illumination, all these techniques are intrinsically destructive in the sense that at least one spontaneous emission is required to infer the qubit state. In this Letter, we demonstrate a cavity assisted qubit detection scheme that enables us to detect the qubit state with almost no photon scattering. We use the fact the atom-cavity system lies in the strong coupling regime, where depending on the internal atomic state we either observe a large or almost zero cavity transmission. Therefore, the role of spontaneous emission is replaced by cavity transmission carrying the necessary information for the state readout. Our results show that with this method we induce three times less scattering than possible a perfect free-space detector for the same detection error.