Frankfurt 2006 – wissenschaftliches Programm
Q 40.4: Vortrag
Mittwoch, 15. März 2006, 11:55–12:10, HI
Experimental Observation of the Four-Photon Entangled State W4(2) — •Christian Schmid1,2, Nikolai Kiesel1,2, Geza Toth1, Enrique Solano1,3, and Harald Weinfurter1,2 — 1Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Str. 1, D-85748 Garching, Germany — 2Department für Physik, Ludwig-Maximilians-Universität, D-80797 München, Germany — 3Sección Física, Dpto. de Ciencias, Pontificia Universidad Católica del Perú, Apartado 1761 Lima, Peru
The entanglement contained in bipartite quantum systems is quite well understood and can easily be quantified. In contrast multipartite quantum systems offer a rich structure of different classes of entanglement. Here it is an entitled question, not only, how strongly but also in particular in which way a quantum system is entangled. It is thus necessary to seek for new multi-qubit quantum states and to investigate their inherent properties in order to get a deeper understanding of multipartite entanglement as well as to find possible applications in quantum communication protocols. We present an experimental examination of a novel four-photon entangled state W4(2) – a four-qubit Dicke state with two excitations. Besides its high entanglement persistency against photon loss it has the remarkable property of connecting the two inequivalent classes of genuine tripartite entanglement via von Neumann measurements on one photon. The state is observed in a simple experimental scheme which allows the accomplishment of a complete quantum state tomography yielding a high fidelity of 0.844 ± 0.008. We further apply novel entanglement witness operators to verify the entanglement properties and discuss applications of the state for quantum telecloning.