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arXiv:1309.2583 · New Journal of Physics

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

Nino Walenta, Andreas Peter Burg, Dario Caselunghe, J Constantin, Nicolas Gisin, Olivier Guinnard, Raphaël Houlmann, Pascal Junod, Boris A. Korzh, Natalia Kulesza, Matthieu Legré, Charles Ci Wen Lim, Tommaso Lunghi, Laurent Monat, Christopher Portmann, Mathilde Soucarros, Rob Thew, Patrick Trinkler, Gregory Trolliet, Fabien Vannel, Hugo Zbinden

Published Jan 23, 2014• 133 citations
arXivHTMLPDF

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-key-size effects, authentication costs and system errors for a security parameter of ε QKD = 4 × 10 −9 .

DOI
10.1088/1367-2630/16/1/013047

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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-key-size effects, authentication costs and system errors for a security parameter of ε QKD = 4 × 10 −9 .
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A high-speed quantum key distribution system was developed with the wavelength-division multiplexing (WDM) technique and dedicated key distillation hardware engines. Two interferometers for encoding and decoding are shared over eight wavelengths to reduce the system's size, cost, and control complexity. The key distillation engines can process a huge amount of data from the WDM channels by using a 1 Mbit block in real time. We demonstrated a three-channel WDM system that simultaneously uses avalanche photodiodes and superconducting single-photon detectors. We achieved 12 h continuous key generation with a secure key rate of 208 kilobits per second through a 45 km field fiber with 14.5 dB loss.
Quantum key distribution (QKD) is the first commercial quantum technology operating at the level of single quanta and is a leading light for quantum-enabled photonic technologies. However, controlling these quantum optical systems in real world environments presents significant challenges. For the first time, we have brought together three key concepts for future QKD systems: a simple high-speed protocol; high performance detection; and integration both, at the component level and for standard fibre network connectivity. The QKD system is capable of continuous and autonomous operation, generating secret keys in real time. Laboratory and field tests were performed and comparisons made with robust InGaAs avalanche photodiodes and superconducting detectors. We report the first real world implementation of a fully functional QKD system over a 43 dB-loss (150 km) transmission line in the Swisscom fibre optic network where we obtained average real-time distribution rates over 3 hours of 2.5 bps.
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Quantum key distribution is an application of quantum physics that allows two distant partners to securely distribute shared random secrets which they can use for secure message encryption, authentication or other communication tasks. In this thesis, I study and implement several concepts, protocols and their components, in particular single photon detectors. I evaluate its compatibility with fiber infrastructures with the aim to improve applicability, performance and profitability of quantum key distribution in different scenarios. I present superconducting single photon detectors implemented for long distance quantum communication, as well as semiconductor detectors employing rapid sine gating schemes. Wavelength-multiplexing of quantum and classical communication channels is demonstrated to stabilize a polarization-encoded quantum channel against birefringence fluctuations, and to realize quantum and encrypted communication over one fiber. An implementation of the coherent one-way protocol is presented which features a hardware distillation engine, wavelength-multiplexing, and an analysis of finite key effects and authentication costs.
We demonstrated ultra fast BB84 quantum key distribution (QKD) transmission at 625 MHz clock rate through a 97 km field-installed fiber using practical clock synchronization based on wavelength-division multiplexing (WDM). We succeeded in over-one-hour stable key generation at a high sifted key rate of 2.4 kbps and a low quantum bit error rate (QBER) of 2.9%. The asymptotic secure key rate was estimated to be 0.78- 0.82 kbps from the transmission data with the decoy method of average photon numbers 0, 0.15, and 0.4 photons/pulse.