MULTI-WAVELENGTH QUANTUM KEY DISTRIBUTION FOR ENHANCED SECURITY AGAINST A PHOTON NUMBER SPLITTING ATTACK AND HIGHER DATA RATES

An arrangement and method for detecting number splitting attacks in quantum key distribution systems is disclosed. According to the method, a receiver may detect the presence of an eavesdropper on a transmission channel by detecting an increase in the percent difference between the photon transmission rates of two signals of different wavelengths. The receiver may directly measure a percent difference in photon receive rates as between the two signals, and compare the measured difference with an expected difference. The expected difference may be known, or may be measured by the receiver on the basis of historical data. The expected difference may be computed from the percent difference between the means of the Poisson distributions of the transmitter's laser sources, which may be determined a priori and communicated to the transmitter.