Experimental realization of Counterfactual Quantum Cryptography
  In counterfactual QKD information is transfered, in a secure way, between Alice and Bob even when no particle carrying the information is in fact transmitted between them. In this letter we fully implement the scheme for counterfactual QKD proposed in [T. Noh, \PRL \textbf{103}, 230501 (2009)], demonstrating for the first time that information can be transmitted between two parties without the transmission of a carrier. 
Giorgio Brida, Andrea Cavanna, Ivo Pietro Degiovanni, Marco Genovese,   Paolo Traina
quant-ph