Kiesel N, Schmid C, Tóth G, Solano E, Weinfurter H
Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Strasse 1, D-85748 Garching, Germany.
Phys Rev Lett. 2007 Feb 9;98(6):063604. doi: 10.1103/PhysRevLett.98.063604. Epub 2007 Feb 7.
We present the experimental observation of the symmetric four-photon entangled Dicke state with two excitations |D_{4};{(2)}. A simple experimental setup allowed quantum state tomography yielding a fidelity as high as 0.844+/-0.008. We study the entanglement persistency of the state using novel witness operators and focus on the demonstration of a remarkable property: depending on the orientation of a measurement on one photon, the remaining three photons are projected into both inequivalent classes of genuine tripartite entanglement, the Greenberger-Horne-Zeilinger and W class. Furthermore, we discuss possible applications of |D_{4};{(2)} in quantum communication.
我们展示了具有两个激发态的对称四光子纠缠狄克态|D₄;{(2)}的实验观测结果。一个简单的实验装置实现了量子态层析成像，得到了高达0.844±0.008的保真度。我们使用新颖的见证算符研究了该态的纠缠持久性，并着重展示了一个显著特性：根据对一个光子测量的取向，其余三个光子会被投影到真正三方纠缠的两个不等价类别，即格林伯格 - 霍恩 - 蔡林格态和W类。此外，我们还讨论了|D₄;{(2)}在量子通信中的可能应用。
