Abstract
We discuss our estimates of the performance of a superconducting single photon detector (SSPD) in a high speed quantum key distribution (QKD) system. We find that at high repetition operation reflections from the readout circuit at room temperature causes an afterpulse-like phenomenon, and drastically increases the quantum bit error rate (QBER). Such effects are not seen during low frequency operation. By using an amplifier with a small reflection coefficient S11, we succeed in reducing the afterpulse-like phenomenon and increasing a secure key rate.
Highlights
Quantum key distribution (QKD) [1,2] is a representative candidate enabling critical issue to be protected in network service
We have developed and demonstrated a three channel wavelength division multiplexing (WDM) QKD that is connected to two sets of superconducting single photon detector (SSPD) developed by NICT [9,10] and one set of semiconductor single photon detectors
The detection efficiency of the SSPDs themselves are about 15% at a dark count (DC) rate of 100 cps, but the total detection efficiency decreases to less than 10% when they are connected to the QKD system
Summary
Quantum key distribution (QKD) [1,2] is a representative candidate enabling critical issue to be protected in network service. We have developed and demonstrated a three channel WDM QKD that is connected to two sets of SSPDs developed by NICT [9,10] and one set of semiconductor single photon detectors. In a single channel with SSPDs, the averaged sifted key and final secure key rates of our QKD system after 45 km transmission through a field installed fiber (14.5dB loss) are. The detection efficiency of the SSPDs themselves are about 15% at a dark count (DC) rate of 100 cps, but the total detection efficiency decreases to less than 10% when they are connected to the QKD system One reason for this discrepancy is due to event selection with a time window of 400 ps. We discuss its origin and present countermeasures against it deteriorating the improvements in QKD performance
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