arXiv:2308.02238 · npj Quantum Information

A hybrid integrated quantum key distribution transceiver chip

Joseph A. Dolphin, Taofiq K. Paraïso, Han Du, Robert I. Woodward, Davide G. Marangon, Andrew J. Shields

Published Sep 6, 2023• 43 citations

Abstract

Abstract Quantum photonic technologies, such as quantum key distribution, are already benefiting greatly from the rise of integrated photonics. However, the flexibility in design of these systems is often restricted by the properties of the integration material platforms. Here, we overcome this choice by using hybrid integration of ultra-low-loss silicon nitride waveguides with indium phosphide electro-optic modulators to produce high-performance quantum key distribution transceiver chips. Access to the best properties of both materials allows us to achieve active encoding and decoding of photonic qubits on-chip at GHz speeds and with sub-1% quantum bit error rates over long fibre distances. We demonstrate bidirectional secure bit rates of 1.82 Mbps over 10 dB channel attenuation and positive secure key rates out to 250 km of fibre. The results support the imminent utility of hybrid integration for quantum photonic circuits and the wider field of photonics.

DOI: 10.1038/s41534-023-00751-3

Related papers

The application of hybrid integrated photonics to quantum communication systems

Joseph A. Dolphin

Quantum key distribution (QKD) is a rapidly maturing quantum photonic technology that allows for the distribution of secure cryptographic keys under no assumptions of the attacker's computing power. A key hurdle for its large-scale adoption is the reduction of its hardware size and cost, for which photonic integration is a promising solution. However, there exists no perfect material platform for this task, and for QKD this leads to either design compromises or core functionalities left off-chip. This thesis makes the assertion that hybrid integrated photonics, where one combines two chip materials into one structure, can resolve some of these issues. Firstly, we present an edge-coupled hybrid transceiver that combines a silicon nitride waveguide chip with an indium phosphide modulator chip. Secondly, we pursue the hybrid integration of the single photon detectors. However, the appropriate solution of fast-gated telecom-wavelength avalanche diodes did not exist, and so in the second experimental chapter of this thesis we develop and characterise a linear array of GHz-gated InGaAs/InP SPADs. Finally, we demonstrate a hybrid integrated QKD receiver, consisting of a silica waveguide chip with the aforementioned SPAD array. This represents the first integrated QKD receiver without requiring either external single photon detectors or cryogenic cooling. The results support the benefits of hybrid integration for quantum key distribution, but also more widely for quantum photonic technology as it continues to emerge.

Sep 30, 20250 citations

High-speed quantum key distribution system

Julius Römer, Erik Jung, Linus Kürpick +3 more

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.

Integrated Optics: Devices, Materials, and TechnologiesJan 24, 20250 citations

Network-ready quantum communication transceivers using hybrid integration

Joseph A. Dolphin, Taofiq K. Paraïso, Han Du +3 more

Using hybrid integration, we overcome usual limitations inherent to specific photonic integration materials and produce high performance quantum transceivers. We measure exceptionally low quantum bit error rates over high channel loss and demonstrate real-world chip-to-chip quantum secure communications over distances beyond the 200 km range.

IET conference proceedings.Nov 13, 20231 citation

Integrated transceiver chip for metropolitan WDM quantum key distributions

Yu Zhou, Yan‐Yang Zhou, Heng Zhang +8 more

The realization of large-scale, practical quantum key distribution (QKD) networks relies on the development of scalable architectures and integrated hardware. We demonstrate a metropolitan wavelength-division multiplexing (WDM) QKD network based on hybrid-integrated quantum node transceiver chips that integrate both transmitter and receiver functionalities, including high-speed pulse modulation, decoy-state modulation, tunable attenuation, time-bin encoding, and decoding. The packaged module offers a wavelength tuning range exceeding 85 nm, with its silicon photonic Mach–Zehnder modulator (MZM) achieving a single-photon equivalent dynamic extinction ratio (SP-EDER) of over 20 dB across the entire tuning range at a 1.25 GHz pulse repetition rate. In combination with a simple 1.25 GHz clocked integrated time-bin QKD system, we generate secret keys at a rate of 865.4 kbps over a channel with 9.08 dB of fixed attenuation and at a rate of 168.2 kbps over a distance of 80 km at 1550.12 nm. Our work demonstrates an integrated WDM QKD network capable of supporting scalable and cost-effective metropolitan quantum-secure communications.

Photonics ResearchJul 1, 20260 citations

High-performance chip-to-chip QKD with hybrid integrated photonics

Joseph A. Dolphin, Taofiq K. Paraïso, Han Du +1 more

Here we demonstrate a hybrid integrated quantum key distribution chip which combines through edge-coupling an ultra-low-loss SiN interferometer with a high-speed InP phase modulator. This novel devices produces record chip-to-chip secure key rates.

Jan 1, 20230 citations

Silicon photonic integrated QKD transceiver utilizing an external cavity laser as the light source

Yu Zhou, Yuyao Guo, Yan-yang Zhou +5 more

Integrated silicon photonics offers a promising route toward compact and CMOS-compatible quantum key distribution (QKD) systems. However, on-chip laser integration remains a key barrier to full system miniaturization. Here, we demonstrate a fully integrated photonic device that combines an external-cavity laser (ECL) with a QKD transceiver, enabled by hybrid III-V/silicon photonic integration. The integrated transmitter and the phase-decoding receiver are combined to form a phase-encoded QKD system that demonstrates quantum bit error rates (QBER) of 1.4% (Z-basis) and 6.4% (X-basis), and a secure key rate of 28.16 kbps over a fiber channel with 8.3 dB loss at 625 MHz. The integrated system achieves a wavelength tunability of 87.61 nm, addressing the challenge of light source integration in silicon-based QKD networks. The demonstrated integration platform represents a crucial step toward the practical integration of QKD into existing optical transport networks (OTNs) and future quantum communication networks.

Optics ExpressFeb 5, 20260 citations