Quote from Bruce Schneiers page :

This presentation will show the first experimental implementation of an eavesdropper for quantum cryptosystem. Although quantum cryptography has been proven unconditionally secure, by exploiting physical imperfections (detector vulnerability) we have successfully built an intercept-resend attack and demonstrated eavesdropping under realistic conditions on an installed quantum key distribution line. The actual eavesdropping hardware we have built will be shown during the conference.
While I am very interested in quantum cryptography, I have never been optimistic about its practicality. And it’s always interesting to see provably secure cryptosystems broken.

Original post can be found here.