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arXiv:2212.12980 · Photonics Research

Resource-efficient quantum key distribution with integrated silicon photonics

Kejin Wei, Xiao Hu, Yongqiang Du, Xin Hua, Zhengeng Zhao, Ye Chen, Chunfeng Huang, Xi Xiao

Published May 17, 2023• 63 citations
arXivHTMLPDF

Abstract

Integrated photonics provides a promising platform for quantum key distribution (QKD) system in terms of miniaturization, robustness, and scalability. Tremendous QKD works based on integrated photonics have been reported. Nonetheless, most current chip-based QKD implementations require additional off-chip hardware to demodulate quantum states or perform auxiliary tasks such as time synchronization and polarization basis tracking. Here, we report a demonstration of resource-efficient chip-based BB84 QKD with a silicon-based encoder and a decoder. In our scheme, the time synchronization and polarization compensation are implemented relying on the preparation and measurement of the quantum states generated by on-chip devices; thus, we need no additional hardware. The experimental tests show that our scheme is highly stable with a low intrinsic quantum bit error rate of 0.50 % ±0.02 % in a 6 h continuous run. Furthermore, over a commercial fiber channel up to 150 km, the system enables the realization of secure key distribution at a rate of 866 bit/s. Our demonstration paves the way for a low-cost, wafer-scale manufactured QKD system.

DOI
10.1364/prj.482942

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Integrated photonics provides a promising platform for quantum key distribution (QKD) system in terms of miniaturization, robustness, and scalability. Tremendous QKD works based on integrated photonics have been reported. Nonetheless, most current chip-based QKD implementations require additional off-chip hardware to demodulate quantum states or perform auxiliary tasks such as time synchronization and polarization basis tracking. Here, we report a demonstration of resource-efficient chip-based BB84 QKD with a silicon-based encoder and a decoder. In our scheme, the time synchronization and polarization compensation are implemented relying on the preparation and measurement of the quantum states generated by on-chip devices; thus, we need no additional hardware. The experimental tests show that our scheme is highly stable with a low intrinsic quantum bit error rate of 0.50 % ±0.02 % in a 6 h continuous run. Furthermore, over a commercial fiber channel up to 150 km, the system enables the realization of secure key distribution at a rate of 866 bit/s. Our demonstration paves the way for a low-cost, wafer-scale manufactured QKD system.
Silicon-based polarization-encoding quantum key distribution (QKD) has been widely studied, owing to its low cost and robustness. However, prior studies have utilized off-chip devices to demodulate the quantum states or perform polarization compensation, given the difficulty of fabricating polarized independent components on the chip. In this paper, we propose a fully chip-based decoder for polarization-encoding QKD. The chip realizes a polarization state analyzer and compensates for the BB84 protocol without requiring additional hardware. It is based on a polarization-to-path conversion method that uses a polarization splitter-rotator. The chip was fabricated using a standard silicon photonics foundry; it has a compact design and is suitable for mass production. In the experimental stability test, an average quantum bit error rate of 0.56%0.56\%0.56% was achieved through continuous operation for 10 h without any polarization feedback. Furthermore, using the developed feedback algorithm, the chip enabled the automatic compensation of the fiber polarization drift, which was emulated by a random fiber polarization scrambler. In the case of the QKD demonstration, we obtained a finite-key secret rate of 240 bps over a fiber spool of 100 km. This study represents an important step toward the integrated, practical, and large-scale deployment of QKD systems.
Silicon (Si) photonics is reaching maturity and has the potential of offering low-cost, reliable, chip-scale systems for quantum key distribution (QKD). On the other hand, QKD is also maturing with the bridging of theory and practice. This work presents a Si integrated photonic transmitter for polarization-encoded QKD. The chip was fabricated in a standard Si photonic foundry process and integrates a pulse generator, intensity modulator, variable optical attenuator, and polarization modulator in a 1.3 mm x 3 mm die area. The devices in the photonic circuit meet the requirements for QKD. The transmitter was used in a proof-of-concept demonstration of the BB84 QKD protocol over a 5 km long fiber link. A quantum bit error rate of 5.4% and an asymptotic secure key rate of 0.95 kbps is obtained. This work shows the feasibility of foundry based Si photonics for quantum information applications.
Measurement-device-independent quantum key distribution (MDI QKD) removes all detector side channels and enables secure QKD with an untrusted relay.It is suitable for building a star-type quantum access network, where the complicated and expensive measurement devices are placed in the central untrusted relay and each user requires only a low-cost transmitter, such as an integrated photonic chip.Here, we experimentally demonstrate a 1.25-GHz silicon photonic chip-based MDI QKD system using polarization encoding.The photonic chip transmitters integrate the necessary encoding components for a standard QKD source.We implement random modulations of polarization states and decoy intensities, and demonstrate a finite-key secret rate of 31 bit=s over 36-dB channel loss (or 180-km standard fiber).This key rate is higher than state-of-the-art MDI QKD experiments.The results show that silicon photonic chipbased MDI QKD, benefiting from miniaturization, low-cost manufacture, and compatibility with CMOS microelectronics, is a promising solution for future quantum secure networks.
Quantum key distribution (QKD) is a quantum communication technology that offers absolute security. Among its various implementations, continuous-variable (CV) QKD has garnered significant attention due to its high secret key generation rates and compatibility with conventional optical telecommunication infrastructure, which operates under ambient conditions. However, chip-based integration is crucial for realizing practical and scalable CV-QKD networks, and photonic integrated circuit technology is a potential solution, leveraging the on-chip integration of essential optical components onto silicon photonic circuits. Therefore, this work presents a compact, stable, and cost-effective quantum photonic CV-QKD system on a chip. Our architecture combines time- and polarization-multiplexing with high-extinction-ratio pulse generation to mitigate excess noise. At the same time, a real-time feedback control mechanism compensates for polarization drift, ensuring robust system performance. Fiber-based evaluations reveal secret key generation rates of 2.55 Mbps over 25 km and 0.737 Mbps over 50 km with 12 h stable operation, establishing, to our knowledge, a new benchmark for integrated photonic CV-QKD systems with both the transmitter and receiver on-chip. These results mark a significant milestone in on-chip quantum communication, paving the way for widespread adoption of photonic integrated circuits in future metropolitan quantum-secure networks.
Photonic chip integration would greatly benefit quantum key distribution (QKD) systems for secure communication, in terms of compactness, scalability, and well-established fabrication techniques. This study demonstrates proof of concept for an all-chip measurement-device-independent QKD system using integrated silicon photonic technology. The prototype generates a key rate per pulse of $2.923\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$ over a distance corresponding to 50 km of standard fiber with 25% detection efficiency; the system is projected to be able to work at 120 km with 85% detection efficiency. This technology shows great promise for highly integrated quantum communication networks.