Alessandro Trenti, Martin Achleitner, Florian Prawits, Bernhard Schrenk, Hauke Conradi, Moritz Kleinert, Alfonso Incoronato, Francesco Zanetto, Franco Zappa, Ilaria Di Luch, Ozan Çirkinoglu, Xaveer J. M. Leijtens, A. Bonardi, Cédric Bruynsteen, Xin Liang Yin, Christian Kießler, Harald Herrmann, Christine Silberhorn, Mathieu Bozzio, Philip John Walther, Hannah Thiel, Gregor Weihs, Hannes Hübel
We present here results of the Quantum Technology Flagship project UNIQORN in the area of integrated photonics for quantum communication applications. Three distinct integration platforms, namely indium phosphide based monolithic integration, polymer-based hybrid integration and the CMOS-compatible silicon platform, have been employed to manufacture components and sub-systems on chip for quantum communication devices. The choice of different platforms was made to exploit the best characteristics of each platform for the intended quantum communication device. The indium phosphide platform was employed to manufacture a transmitter chip for quantum key distribution featuring laser, modulators, and attenuators. The transmitter chip was evaluated in a QKD experiment achieving a secure rate of 1 kbit/s. The polymer platform was investigated for engineering non-classical light sources. Entangled and heralded single-photon sources, based on non-linear optics, were assembled on the polymer in a hybrid fashion together with waveguides and other passive micro-optical elements. A quantum random number generator, featuring a 70% randomness extraction efficiency, was also fabricated using the polymer integration technique. An array of 32 individual single-photon avalanche diodes, operating at room temperature and featuring an onboard coincidence logic, was coupled to the chip to demonstrate direct detection of photons on the polymer. Finally, a transimpedance amplifier based on gallium arsenide high electron mobility transistors was produced with an exceptional large electrical noise clearance of 28 dB at 100 MHz.
We present here results of the Quantum Technology Flagship project UNIQORN in the area of integrated photonics for quantum communication applications. Three distinct integration platforms, namely indium phosphide based monolithic integration, polymer-based hybrid integration and the CMOS-compatible silicon platform, have been employed to manufacture components and sub-systems on chip for quantum communication devices. The choice of different platforms was made to exploit the best characteristics of each platform for the intended quantum communication device. The indium phosphide platform was employed to manufacture a transmitter chip for quantum key distribution featuring laser, modulators, and attenuators. The transmitter chip was evaluated in a QKD experiment achieving a secure rate of 1 kbit/s. The polymer platform was investigated for engineering non-classical light sources. Entangled and heralded single-photon sources, based on non-linear optics, were assembled on the polymer in a hybrid fashion together with waveguides and other passive micro-optical elements. A quantum random number generator, featuring a 70% randomness extraction efficiency, was also fabricated using the polymer integration technique. An array of 32 individual single-photon avalanche diodes, operating at room temperature and featuring an onboard coincidence logic, was coupled to the chip to demonstrate direct detection of photons on the polymer. Finally, a transimpedance amplifier based on gallium arsenide high electron mobility transistors was produced with an exceptional large electrical noise clearance of 28 dB at 100 MHz.
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.
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.
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.
Quantum key distribution (QKD) relies on the fundamental principles of quantum mechanics and can theoretically achieve unconditionally secure communication that is provable by information theory. Quantum random number generators, on the other hand, utilize the inherent randomness of quantum phenomena and are capable of generating a truly random entropy source that is unpredictable, unbiased and unrepeatable. These two technologies are crucial for building highly trustworthy and secure communication systems resistant to quantum attacks. However, their large-scale deployment still faces challenges such as system performance optimization, cost control and scale production. Relying on wafer-level fabrication platforms and micro-nanometer processing, integrated photonics technology integrates the core devices of traditional QKD systems (e.g., light source, modulator, and detector) in a single chip at high density. It significantly improves the miniaturization, operational stability and cost-effectiveness of the system, and enhances the intrinsic security, and becomes a key enabling platform to drive QKD and QRNG from laboratory to engineering applications. In this paper, we systematically review the recent breakthroughs of photonic integrated QKD based on different material platforms (SOI/InP/TFLN/Si3N4) in terms of core metrics, such as transmission distance and key rate, as well as the significant breakthroughs of integrated QRNG in terms of random number generation rate and system integration. Finally, the future development direction of this field is discussed and outlooked from the four dimensions of practical security of QKD systems, on-chip implementation of cutting-edge QKD protocols, practical fully-integrated QKD systems, and synergistic optimization of high performance and high integration of integrated QRNG.
Silicon quantum photonics, capable to integrate large numbers of optical components with CMOS-compatible fabrication technology and reliable control of quantum states, is expected to play a critical role in future quantum communication. In this talk, we will introduce our recent results of silicon photonics for quantum communication, including high-dimensional silicon chip-to-chip quantum key distribution, chip-to-chip quantum teleportation, on-chip generation of high-dimensional quantum entanglement, and Hong-Ou-Mandel interference between two different III-V/silicon hybrid lasers towards future measurement device independent quantum communication.
The capability of realizing quantum photonics implementations on-chip will have a strong impact on several aspects of quantum computation and information processing. The implementation of large scale integrated quantum photonic technologies requires on-chip reconfigurable waveguide circuits as well as single-photon sources and detectors. Many successes have been made in recent years to demonstrate complex quantum circuits in many material platforms. Among all these platforms, the Silicon-on-Insulator (SOI) platform is outstanding as it is well developed for classical applications and therefore deploys a high component density, mature fabrication techniques and compatibility with the telecom regime and the complementary metal-oxide-semiconductor (CMOS) technology. However, the lack of on-demand non-classical light sources, directly incorporated in silicon chips, forces the use of nonlinear processes to generate non-classical light states: the probabilistic nature of the emission process sets a limit in the maximally achievable experimental complexity. The use of on-demand sources will have a strong impact on the device’s scalability.