Experimental Atom-Photon Entanglement:

Entanglement between light and matter is a key resource for new applications in quantum communication and information forming the interface between atomic quantum memories and photonic quantum communication channels [1,2]. Especially for applications like quantum networks or the quantum repeater, atom-photon entanglement enables one to generate entanglement between atoms at remote locations [2,3]. Here we report the observation of high-fidelity entanglement between a single optically trapped $^{87}$Rb atom and a single spontaneously emitted photon at a wavelength of 780 nm. To verify the entanglement we introduce a single atom state analysis. This technique is used for full state tomography of the atom-photon qubit-pair. The efficiency of the atomic state detection and the observed entanglement fidelity are high enough to allow in a next step the generation of entangled atoms at large distances, ready for a final loophole-free test of Bell's inequality. [1] B. Blinov et al., Nature {\bf 428}, 153 (2004). [2] J. Volz \& M. Weber et al., Phys. Rev. Lett. {\bf 96}, (2006). [3] C. Simon et al., Phys. Rev. Lett. {\bf 91}, 110405 (2003).