Entangled state quantum cryptography: eavesdropping on the ekert protocol
Using polarization-entangled photons from spontaneous parametric down-conversion, we have implemented Ekert's quantum cryptography protocol. The near-perfect correlations of the photons allow the sharing of a secret key between two parties. The presence of an eavesdropper is continually checked by measuring Bell's inequalities. We investigated several possible eavesdropper strategies, including pseudo-quantum-nondemolition measurements. In all cases, the eavesdropper's presence was readily apparent. We discuss a procedure to increase her detectability.
Naik
DS
Physics Division, P-23, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
Peterson
CG
White
AG
Berglund
AJ
Kwiat
PG