A fast and versatile quantum key distribution system with hardware key distillation and wavelength multiplexing

Abstract

We present a compactly integrated, 625 MHz clocked coherent one-way quantum key distribution system which continuously distributes secret keys over an optical fibre link. To support high secret key rates, we implemented a fast hardware key distillation engine which allows for key distillation rates up to 4 Mbps in real time. The system employs wavelength multiplexing in order to run over only a single optical fibre. Using fast gated InGaAs single photon detectors, we reliably distribute secret keys with a rate above 21 kbps over 25 km of optical fibre. We optimized the system considering a security analysis that respects finite-keysize effects, authentication costs and system errors for a security parameter of ε QKD = 4 × 10 −9 .

Free-running InGaAs single photon detector with 1 dark count per second at 10% efficiency

“…The system is clocked at 625 MHz and incorporates all of the necessary components for full quantum key distribution, including real-time post-processing for error correction, privacy amplification and authentication. 18 The implementation is based on the coherent-one way protocol 19 which uses two detectors, one for measuring the bit value encoded in the photon arrival time (data detector) and a second one to measure the visibility of the coherent state interference (monitor detector), which guarantees security. Due to their extremely low dark count rates, the detectors presented in this Letter are especially suited for utilization in QKD scenarios with very long fiber lengths.…”

“…The secret key rates presented here are the final output rates from the privacy amplification, after the deduction of secret keys that are used for the classical channel authentication. The hardware key distillation engine 18 processes the keys continuously in real-time, without the need for long, individual key sessions. The maximum channel losses presented here are typically not achievable with systems based on InGaAs detectors and would usually require the use of SNSPDs.…”

Detector-device-independent quantum key distribution

“…[19][20][21][22] In particular, ultra-fast generation of polarization states could be achieved using a birefringence modulator scheme as used in Ref. 43.…”

“…First, the achievable secure key rates (SKR) are significantly lower compared to point-to-point 18 prepare-and-measure (P&M) QKD systems. [19][20][21][22] This is mainly because a twophoton BSM relies on coincidence detections, meaning that the SKR scales with (g det P 1 (l)) 2 , where g det is the efficiency of the single photon detector (SPD) and P 1 (l) is the probability of the source emitting a single-photon. 23 Note, however, that coincidence detections make mdiQKD more robust against detector dark counts.…”

A Pipeline Optimization Model for QKD Post-processing System

“…Due to its high complexity, the design and implementation of post-processing has a huge influence on the speed of security key generation. For highspeed QKD systems, most works utilize hardware for real-time post-processing [3][4][5][6][7][8]. However, hardware based methodology suffers from long design cycle, high complexity in realization and troublesome debugging.…”