Experimental Test of Two-way Quantum Key Distribution in Presence of   Controlled Noise
  We describe the experimental test of a quantum key distribution performed with a two-way protocol without using entanglement. An individual incoherent eavesdropping is simulated and induces a variable amount of noise on the communication channel. This allows a direct verification of the agreement between theory and practice. 
A. Cere', M. Lucamarini, G. Di Giuseppe and P. Tombesi