Abstract
We report a demonstration of quantum key distribution (QKD) at gigahertz clock rates with InGaAs avalanche photodiodes (APDs) operating in a self-differencing mode. Such a mode of operation allows detection of extremely weak avalanches so that the detector afterpulse noise is sufficiently suppressed. The system is characterized by a secure bit rate of 2.37Mbit∕s at 5.6km and 27.9kbit∕s at 65.5km when the fiber dispersion is not compensated. After compensating the fiber dispersion, the QKD distance is extended to 101km, resulting in a secure key rate of 2.88kbit∕s. Our results suggest that InGaAs APDs are very well suited to gigahertz QKD applications.
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