Dense Coding in Experimental Quantum Communication.

Quantum correlations and entanglement in many-particle systems can be used to significantly increase and extend the performance of standard communication and computation techniques. Common to these methods is the joint measurement of two two-state particles in the so-called EPR-Bell-state basis, consisting of the four maximally entangled states of this two-particle system. In our experimental realizations we use interferometric EPR-Bell-state analysis, which allows us to transfer one of three messages per two-state particle (compared with the classical maximum of one of two) and to perform the teleportation with an efficiency of 50%.