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arXiv:2610.35410

Multimode continuous-variable quantum key distribution with CMOS-compatible photonic-electronic integration

Yiming Bian, Sarah Bastiaens, Saeed Hakimi, Huy Quang Nguyen, Aboobackkar Sidhique, Cédric Bruynsteen, Govind J. Wanjalkar, Ali Al Hadi Amhaz, Jasper Jans, Axl Bomhals, Ulrik L. Andersen, Tobias Gehring, Xin Yin, Adnan A. E. Hajomer

quant-phSubmitted Oct 26, 2026• Announced Oct 27, 2026• 0 citations
arXivHTMLPDF

Abstract

Multiplexing and photonic-electronic integration offer a route to scalable and high-throughput quantum key distribution (QKD) networks through parallel transmission and compact hardware suited to volume manufacturing. Realizing this route requires multichannel transmitters and receivers, and a security analysis accounting for mode coupling. Here we present a CMOS-compatible photonic-electronic multimode continuous-variable QKD architecture, using polarization multiplexing as a two-mode example. Silicon-photonic transmitter and receiver chips prepare and detect two polarization modes in parallel. The receiver is co-integrated with a dual-channel 28-nm CMOS transimpedance amplifier, providing shot-noise clearances exceeding 20 dB in both channels. Pilot-assisted unitary digital recovery removes the need for active optical polarization control, while a multimode security analysis accounts for the mode crosstalk. At 2 percent residual crosstalk, the multimode analysis extends the simulated secure distance from 39 to 84 km, near the crosstalk-free limit of 89 km. Over 10 km of deployed fibre, the mean total finite-size secret-key rate estimate is 6.69 Mbit/s, 12 percent above the single-mode analysis from the same digitally recovered data. These results establish a route to scalable multimode quantum-secured networks built on technology suited to mass production.

AI Summary

The paper addresses parallel continuous-variable QKD with integrated hardware when imperfect mode separation leaves crosstalk that single-mode security analyses count as excess noise. It combines silicon-photonic transmitters and receivers, dual-channel 28-nm CMOS electronic readout, unitary digital polarization recovery, and a multimode security analysis. For each receiver mode, the analysis retains correlations with all independently prepared, trusted source modes while conservatively assigning other receiver modes to Eve. Gaussian covariance matrices bound Eve’s Holevo information under collective attacks; finite-size parameter estimation uses multivariate regression confidence regions and a numerical worst-case search. Reconciliation still uses only the intended source–receiver pair. Distinguishable pilots estimate polarization mixing, whose nearest unitary matrix is inverted digitally rather than using active optical polarization control. The two-polarization receiver achieves over 20 dB shot-noise clearance in both channels across approximately 0.1–1 GHz. Over 10 km of deployed fibre, at 125 MBaud per polarization, ten measurement rounds yield a mean total finite-size secret-key rate estimate of 6.69 Mbit/s, versus 5.97 Mbit/s from single-mode analysis of the same recovered data—a 12% increase. Simulations with ideal detectors and 2% residual crosstalk extend estimated secure reach from 39 to 84 km, compared with 89 km without crosstalk. Error correction and privacy amplification are not executed, and composable security remains future work. The experiment uses shared-clock, co-located endpoints and external optical components. Detection efficiency is 0.334, primarily limited by coupling; higher-mode finite-size penalties and worst-case-search scaling remain unquantified.

Little sign of AI-generated textStrong assumptions

Central claim may not hold: The reported finite-size security against collective attacks relies on confidence regions proved only for Gaussian regression residuals, an additional restriction not supplied by Gaussian optimality of the Holevo bound. The numerical search reports a worst-case candidate without demonstrating that its Holevo information upper-bounds the entire permitted confidence region, leaving the security conservativeness of the reported rates unverified.

Written by gpt-6.1-sol from the paper's full text. Automated: it can be wrong.

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Multiplexing and photonic-electronic integration offer a route to scalable and high-throughput quantum key distribution (QKD) networks through parallel transmission and compact hardware suited to volume manufacturing. Realizing this route requires multichannel transmitters and receivers, and a security analysis accounting for mode coupling. Here we present a CMOS-compatible photonic-electronic multimode continuous-variable QKD architecture, using polarization multiplexing as a two-mode example. Silicon-photonic transmitter and receiver chips prepare and detect two polarization modes in parallel. The receiver is co-integrated with a dual-channel 28-nm CMOS transimpedance amplifier, providing shot-noise clearances exceeding 20 dB in both channels. Pilot-assisted unitary digital recovery removes the need for active optical polarization control, while a multimode security analysis accounts for the mode crosstalk. At 2 percent residual crosstalk, the multimode analysis extends the simulated secure distance from 39 to 84 km, near the crosstalk-free limit of 89 km. Over 10 km of deployed fibre, the mean total finite-size secret-key rate estimate is 6.69 Mbit/s, 12 percent above the single-mode analysis from the same digitally recovered data. These results establish a route to scalable multimode quantum-secured networks built on technology suited to mass production.
The paper addresses parallel continuous-variable QKD with integrated hardware when imperfect mode separation leaves crosstalk that single-mode security analyses count as excess noise. It combines silicon-photonic transmitters and receivers, dual-channel 28-nm CMOS electronic readout, unitary digital polarization recovery, and a multimode security analysis.
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Quantum key distribution (QKD) is a widely recognized application of quantum information theory, guaranteeing information-theoretically secure key exchange. However, commercial viability of QKD systems is currently impeded by issues such as scalability, network integration, and high manufacturing costs. Low-cost, high-volume production of photonic and electronic integrated circuits could be the breakthrough needed for broad-scale deployment of cutting-edge QKD systems. Here, we present a continuous-variable (CV) QKD system that is based on an integrated photonic-electronic receiver. It combines a silicon photonic integrated circuit, featuring a phase-diverse receiver, with custom-designed GaAs pHEMT transimpedance amplifiers. Operating at a classical telecom symbol rate of 10 GBaud, our QKD system generates high secret key rates - exceeding 0.7 Gb/s over a 5 km distance and 0.3 Gb/s over a 10 km. The secret keys are secure against collective attacks, even when accounting for finite-size effects in the parameter estimation, thanks to well-designed digital signal processing that enables broadband system operation. Our experiment sets a record for secure key exchange and paves the way for the implementation of real-time broadband CV-QKD systems.
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.
Quantum key distribution (QKD) stands as the most successful application of quantum information science, providing information-theoretic security for key exchange. While it has evolved from proof-of-concept experiments to commercial products, widespread adoption requires chip-based integration to reduce costs, enable mass production, facilitate miniaturization, and enhance system performance. Here, we demonstrate a fully photonic-integrated continuous-variable QKD (CV-QKD) system operating at a classical telecom symbol rate of 16 GBaud. Our system integrates a silicon photonic transmitter circuit (excluding the laser source) and a 20 GHz shot-noise-limited photonic–electronic receiver, which features a phase-diverse silicon photonic integrated circuit and custom-designed GaAs pHEMT transimpedance amplifiers. Advanced digital signal processing allows our system to achieve a secure key rate for discrete-modulated coherent state CV-QKD that reaches 0.289 Gb/s and 0.246 Gb/s over a 20 km fiber link in the asymptotic regime and with finite-size parameter estimation, respectively. These results represent a critical step toward scalable, cost-effective, and mass-deployable quantum-secure communication using photonic-integrated CV-QKD systems.
Quantum key distribution (QKD) is a prominent application in the field of quantum cryptography, providing information-theoretic security for secret key exchange. The implementation of QKD systems on photonic integrated circuits (PICs) can reduce the size and cost of such systems and facilitate their deployment in practical infrastructures. To this end, continuous-variable (CV) QKD systems are particularly well-suited as they do not require single-photon detectors, whose integration is presently challenging. Here we present a CV-QKD receiver based on a silicon PIC capable of performing balanced detection. We characterize its performance in a laboratory QKD setup using a frequency multiplexed pilot scheme with specifically designed data processing allowing high modulation and secret key rates. The obtained excess noise values are compatible with asymptotic secret key rates of 2.4 Mbit/s and 220 kbit/s at an emulated distance of 10 km and 23 km, respectively. These results demonstrate the potential of this technology toward fully integrated devices suitable for high-speed, metropolitan-distance secure communication.
Quantum key distribution (QKD) is a well-known application of quantum information theory that guarantees information-theoretically secure key exchange. As QKD becomes more and more commercially viable, challenges such as scalability, network integration, and high production costs need to be addressed. Photonic and electronic integrated circuits that can be produced in large volumes at low cost hold the key to large-scale deployment of next-generation QKD systems. Here, we present a continuous-variable (CV) QKD system using an integrated photonic-electronic receiver that combines a silicon photonic integrated circuit implementing a phase-diverse receiver with custom-designed GaAs pHEMT transimpedance amplifiers. The QKD system operates at a classical telecom symbol rate of 10 GBaud, generating high secret key rates exceeding 0.7 Gb/s over a distance of 5 km and 0.3 Gb/s over a distance of 10 km. The secret keys are secure against collective attacks with finite-size effects taken into account. Well-designed digital signal processing enabled the high-speed operation. Our experiment sets a new record for secure quantum communication and paves the way for the next generation of CV-QKD systems.
Quantum key distribution (QKD) guarantees information-theoretic security by the laws of physics, but deployment at scale requires compact, manufacturable photonic terminals. Continuous-variable QKD (CV-QKD) is well suited for this transition through telecom-compatible, room-temperature coherent detection. However, unifying full on-chip core terminal integration, room-temperature operation, high loss tolerance, and composable end-to-end security in long-distance QKD remains a key bottleneck. Here we report a fully integrated CV-QKD platform in which two hybrid III--V/Si3_33​N4_44​ integrated lasers, a silicon transmitter, and a silicon coherent receiver implement the core terminal functions, operating with a local local oscillator (LLO) over fibre links of 25--150 km. A Bayesian machine-learning algorithm maintains robust phase lock throughout the long records required for composable security, consistently outperforming the conventional unscented Kalman filter, while rate-matched multidimensional reconciliation approaches the Shannon limit. The system certifies a composable finite-size secret-key rate of 29.3 kbps at 100 km from a 140-billion-symbol block, with 12.9 kbps at 125 km under finite-size analysis and 9.17 kbps at 150 km under asymptotic analysis. By establishing the longest finite-size and asymptotic reaches and the highest secret-key rate per symbol reported for integrated CV-QKD, this work advances the development of practical chip-based quantum networks.