In this work we propose a switchable dual bandwidth optical receiver that can be used for both classical and continuous variable quantum key distribution (CV-QKD) on a monolithic platform for opto-electronic integration. Switchable transimpedance amplifier is designed for dual bandwidth that can be switched between high bandwidth (10 GHz) for classical and low bandwidth (>1.5GHz) for quantum communication. Monolithic approach allows integration of photonics on the same chip which allows for low-noise operation as well as reconfigurable configuration between a simple link for on-off keying used for classical and optical heterodyne coherent reception used for quantum communication. The receiver performance for both classical and quantum application is simulated showing very high sensitivity as well as high secure key rates over moderate distances.
In this work we propose a switchable dual bandwidth optical receiver that can be used for both classical and continuous variable quantum key distribution (CV-QKD) on a monolithic platform for opto-electronic integration. Switchable transimpedance amplifier is designed for dual bandwidth that can be switched between high bandwidth (10 GHz) for classical and low bandwidth (>1.5GHz) for quantum communication. Monolithic approach allows integration of photonics on the same chip which allows for low-noise operation as well as reconfigurable configuration between a simple link for on-off keying used for classical and optical heterodyne coherent reception used for quantum communication. The receiver performance for both classical and quantum application is simulated showing very high sensitivity as well as high secure key rates over moderate distances.
In this work we explore monolithic optoelectronic integration platform for significant down-scaling of input-referred noise in custom designed low-noise analog front-end used for balanced photodetection. The performance of such monolithically integrated approach is compared to heterogeneously integrated solution designed in the same technology which requires wire-bonding to the balanced photodetectors. The designed circuits are targeting bandwidth above 1GHz. The improved noise performance is leveraged against increased secure key rates and achievable reach in continuous-variable quantum key distribution (CVQKD).
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.
We present a design of balanced homodyne receivers suitable for ultra-low noise quantum applications such as continuous-variable quantum key distribution and quantum random number generation. For best noise and bandwidth performance a die-level low-parasitic photodiode together with a low-noise high-speed transimpedance amplifier are explored together with a planar lightwave circuit splitter chip serving as a photomixer. Bandwidths of 750 MHz and 2.6 GHz were accomplished while maintaining optimum noise performance, as evidenced by very high quantum-to-classical noise ratios of 26.8 and 18.6 dB, respectively. A common-mode rejection ratio of at least 40 dB was achieved for a frequency range of up to 1 GHz. Its application for continuous-variable quantum key distribution was evaluated by means of estimations under a strict untrusted receiver assumption, showing its potential for generating up to 43 Mbit/s secure-key rate over a reach of 10 km, whereas up to 100 Mbit/s could be supported at shorter reaches. Moreover, the high quantum-to-classical clearance values can enable high quality quantum random number generation at Gb/s rates. The multi-purpose operation of the designed balanced receivers for classical communications was examined showing reception sensitivities of −55.8 and −52.6 dBm at 500 Mbit/s and 1 Gbit/s quadrature phase shift keying transmission, respectively, using the 750 MHz receiver. The faster 2.6 GHz receiver enabled 10 Gbit/s duobinary transmission at −14.8 dBm sensitivity.
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 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.
Continuous variable quantum key distribution (CV-QKD) and continuous variable quantum random number generation (CV-QRNG) are critical technologies for secure communication and high-speed randomness generation, exploiting shot-noise-limited coherent detection for their operation. Integrated photonic solutions are key to advancing these protocols, as they enable compact, scalable, and efficient system implementations. We introduce femtosecond laser micromachining (FLM) on borosilicate glass as a platform for producing photonic integrated circuits (PICs) realizing coherent detection suitable for quantum information processing. Employing off-chip detectors, we exploit the specific features of FLM to produce a PIC designed for CV-QKD and CV-QRNG applications. The PIC features fully adjustable optical components that achieve precise calibration and reliable operation under protocol-defined conditions. The device exhibits low insertion losses (≤1.28 dB), polarization-insensitive operation, and a common-mode rejection ratio exceeding 73 dB. These characteristics allowed the experimental realization of a source-device-independent CV-QRNG with a secure generation rate of 42.74 Gbit/s and a quadrature phase-shift-keying-based CV-QKD system achieving a secret key rate of 3.2 Mbit/s. Our results highlight the potential of FLM technology as an integrated photonic platform, paving the way for scalable and high-performing quantum communication systems.