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Integrated Photonic Devices for Quantum Key Distribution

Philip Sibson, Mark Godfrey, Chris Erven, Shigehito Miki, Taro Yamashita, Mikio Fujiwara, Masahide Sasaki, Hirotaka Terai, Michael G. Tanner, Chandra M. Natarajan, Robert H. Hadfield, Jeremy L. O’Brien, Mark G. Thompson

Published Jan 1, 2015• 3 citations
Publisher

Abstract

We demonstrate a fully integrated photonic transmitter for time-bin based multi-protocol quantum key distribution. This GHz rate Indium Phosphide device prepares states for Coherent One Way (COW), Differential Phase Shift (DPS), and BB84 protocols.
DOI
10.1364/cleo_qels.2015.ff1a.6

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Improvement in secure transmission of information is an urgent need for governments, corporations and individuals. Quantum key distribution (QKD) promises security based on the laws of physics and has rapidly grown from proof-of-concept to robust demonstrations and deployment of commercial systems. Despite these advances, QKD has not been widely adopted, and large-scale deployment will likely require chip-based devices for improved performance, miniaturization and enhanced functionality. Here we report low error rate, GHz clocked QKD operation of an indium phosphide transmitter chip and a silicon oxynitride receiver chip-monolithically integrated devices using components and manufacturing processes from the telecommunications industry. We use the reconfigurability of these devices to demonstrate three prominent QKD protocols-BB84, Coherent One Way and Differential Phase Shift-with performance comparable to state-of-the-art. These devices, when combined with integrated single photon detectors, pave the way for successfully integrating QKD into future telecommunications networks.
In this work, an indium phosphide (InP) based quantum key distribution (QKD) transmitter on a photonic integrated circuit (PICs) is examined. The PIC, which was designed by the authors from Eindhoven University of Technology, and characterised in the QKD system by the authors from Austrian Institute of Technology, features a ring laser structure, a single Mach-Zehnder modulator (MZM) structure with integrated radio frequency (RF) phase modulators for pulse carving, intensity modulation and phase modulation and an absorber for attenuation. The individual components were characterised. Additionally, the PIC was tested in a 4-state time-bin BB84 protocol including a bulk receiver, key performance measures like quantum bit error rate (QBER) and secret key rate (SKR) were analysed. The high performance PIC is capable of generating a SKR in the kbits/s range exhibiting high stability over a measured time frame of around an hour.
Advances in quantum computing pose significant threats to the security of conventional encryption standards. Although quantum key distribution systems offer inherent security, they face challenges in achieving practical secret-key rates over long transmission distances. Photonic Integrated Circuit technologies provide scalability and system efficiency for high key rates using multiplexed time-bin protocols. We present the architecture of a 16-channel multiplexed QKD system at a GHz clock rate realized on integrated photonic chips, promising further scalability. The sender module revolves around an indium-phosphide chip featuring tunable lasers, modulators, and combiners. On the receiver side, low fiber-to-chip coupling loss and waveguide-integrated superconducting nanowire single-photon detectors on silicon nitride provide the necessary detection efficiency.