Co-integration of microelectronics and integrated photonics for quantum technologies
Lead Research Organisation:
KETS Quantum Security Ltd
Department Name: CEO
Abstract
The advent of practical quantum computers, expected within the next two decades, poses a serious threat to most of standard encryption systems. Quantum Key Distribution (QKD) and Quantum Random Number Generators (QRNGs) aim to enhance security of communications and personal data by exploiting the laws of Quantum Mechanics and provide the solution to threat caused by a malicious use of quantum computers. QRNGs, exploiting the probabilistic nature of quantum measurements, produce truly random numbers. This is in opposition with current methods to generate random numbers which combine the use of chaotic systems and software-based pseudo random number generators. QKD systems taking advantage specific features of quantum systems such as superposition of quantum states and the "no-cloning" theorem enable parties to exchange cryptographic keys in an intrinsically secure way. Because QKD key exchange is based on physical systems as opposed to software-based encryption methods, QKD is also "future-proof" as no improvement on hacking algorithm will affect the security of the protocols.
In the last few years, the efforts of the QKD and QRNG community have focused first to produce lab prototypes and more recently to provide commercial systems, which have been deployed in small scale around the globe. However, less focus has been placed on key aspects such as the form factor and technology scalability as well as power consumption and costs. Systems built with optical fibres and discrete electronics components are inevitably expensive, bulky, and limited in terms of performance and therefore intrinsically not scalable. KETS Quantum Security Ltd, spin-off of the Quantum Engineering Technology Labs (University of Bristol) has been addressing the scalability issues by combining the advantages of integrated photonics technologies and quantum cryptography protocols.
While the integrated photonic chips have significantly reduced the size of the core optical system, separation between discrete electronic components and photonic chips inherently limits the overall performance of the quantum technology. Moreover, this increases the size of the devices and their costs, limiting the spread of this QKD and QRNG systems.
The focus of this fellowship would be the development of some novel critical integrated opto-electronics systems, where microelectronics and quantum photonics will be monolithically integrated on the same semiconductor substrate. Monolithic integration of electronics and photonics is a critical technological step forward that will open the way to a whole new range of solutions and will improve the performance of quantum technologies potentially by orders of magnitude. This could bring groundbreaking improvements to QKD and QRNG systems, opening the way to their direct integration onto modern digital technologies.
In the last few years, the efforts of the QKD and QRNG community have focused first to produce lab prototypes and more recently to provide commercial systems, which have been deployed in small scale around the globe. However, less focus has been placed on key aspects such as the form factor and technology scalability as well as power consumption and costs. Systems built with optical fibres and discrete electronics components are inevitably expensive, bulky, and limited in terms of performance and therefore intrinsically not scalable. KETS Quantum Security Ltd, spin-off of the Quantum Engineering Technology Labs (University of Bristol) has been addressing the scalability issues by combining the advantages of integrated photonics technologies and quantum cryptography protocols.
While the integrated photonic chips have significantly reduced the size of the core optical system, separation between discrete electronic components and photonic chips inherently limits the overall performance of the quantum technology. Moreover, this increases the size of the devices and their costs, limiting the spread of this QKD and QRNG systems.
The focus of this fellowship would be the development of some novel critical integrated opto-electronics systems, where microelectronics and quantum photonics will be monolithically integrated on the same semiconductor substrate. Monolithic integration of electronics and photonics is a critical technological step forward that will open the way to a whole new range of solutions and will improve the performance of quantum technologies potentially by orders of magnitude. This could bring groundbreaking improvements to QKD and QRNG systems, opening the way to their direct integration onto modern digital technologies.
Organisations
| Description | We have so far focused on the validation of photonic integrated circuits for quantum cryptography applications. Particularly, we have investigated the direct use of Indium Phosphide manufactured in commercial foundries for quantum random number generators and quantum key distribution systems. We have analyzed and tested a number of building blocks and circuits which have so far showed positive results. If confirmed, this will pave the way to a significant reduction of costs (x5 cost reduction estimated compared to commercially available quantum key distribution systems) and form factor (from rack mounted units to PCIe cards) of quantum cryptography systems. A portfolio of high-speed electronic integrated circuits, under development, will further help the reduction of costs and form factor. |
| Exploitation Route | From an industrial perspective I expect these results will support the long term wider use of quantum cryptography technologies. From a research perspective, once these results will be ready for publication, it will significantly contribute to inform the quantum cryptography research community to explore new methods to operate chip-based systems. It will also potentially inform the technology development roadmap of photonic foundries who might try to accommodate new requirements. |
| Sectors | Aerospace Defence and Marine Digital/Communication/Information Technologies (including Software) Electronics |
| Description | One of the devices (optically-self contained QRNG) reported from earlier years of the FLF have now been integrated in our commercial systems. |
| First Year Of Impact | 2023 |
| Sector | Digital/Communication/Information Technologies (including Software),Electronics |
| Impact Types | Economic |
| Description | Collaboration |
| Organisation | TÃœV Nord Group |
| Department | Alter Technology TUV Nord UK Limited |
| Country | United Kingdom |
| Sector | Private |
| PI Contribution | I coordinated the participation of KETS Quantum Security Ltd in a consortium to develop highly efficient packaging solutions for quantum networking applications. This consortium, led by Alter Technology UK sees the participation of academic institutions (University of Bristol and University of Sheffield), as well as industrial partners (KETS, Wave Photonics, Senko). The consortium was awarded a Quantum Missions Pilot award. Although technically outside my FLF scope, this activity will well complement my FLF activities by fostering new collaborations within the UK industry. I will cover an industrial advisory role to provide insight regarding the technical and commercial needs as seen by a supplier of quantum networks solutions. This will indirectly feed into the FLF activities by inspiring technical solutions and solving supply chain and manufacturing challenges. |
| Collaborator Contribution | The project has been awarded and it will start in April 2025. No actual contributions have been made yet. |
| Impact | The collaboration has yet to start |
| Start Year | 2025 |
| Title | Bench-top continuous-variable quantum key distribution (WP2) |
| Description | We completed the development of a bench-top optical and electrical setup to perform continuous-variable quantum key distribution (CV-QKD) protocols (It contributes to the objective of WP2). The setup was conveniently built making use of off-the-shelf optical and electronic components. The optical off-the-shelf components, such as a Lithium Niobate modulators and InGaAs balanced detectors, have very high specifications. Similarly the electronics are T&M equipment and evaluation kits that provide very high-performance. Particularly, some high-speed data converters components are in the form of evaluation boards to provide easy user interfaces and operation. With this system we have demonstrated operational CV-QKD protocols comparable to recent literature, with off-line estimated secret key rate of 5 Mbps at 20km. In our demonstration, we made use of a Gaussian modulated coherent state quantum key distribution protocol by generating probabilistically shaped 16/32/64-QAM with the so-called local Local Oscillator approach. This setup is also currently used as a benchmark in the development of our chip-based photonic-electronic CV-QKD system. Each subsystem of the bench-top system can be replaced with alternative parts, with slightly different specifications and performance, including our own chip-based solutions. This provide a quick and relatively easy way to compare our devices with a system that shows almost ideal behavior. We expect this to provide an added value to the development of our final product. If deemed opportune, the bench-top solution will be turned into 2U-rack transmitter and receiver units to be deployed on-field to help interactions with partners and shape the technical details of our final chip-based prototype. |
| Type Of Technology | Systems, Materials & Instrumental Engineering |
| Year Produced | 2023 |
| Impact | This system was meant as an internal tool that will support the development of our bespoke system. It was not meant to produce external impact. |
| Title | Full software simulation stack for continuous-variable quantum key distribution systems (WP2) |
| Description | The software simulates an experimental continuous-variable quantum key distribution and the relative post-processing software stack. The software simulates the generation of normally distributed optical quantum states, their transmission through a quantum channel and the measurement apparatus. An extensive set of experimental parameters can be varied, to test the system in a variety of different potential real-world conditions. Parameters that can be varied are the following: the size of the alphabet of the quantum signals sent, the distance of communication link, the losses incurred at the measurement apparatus and its efficiency. The software produces the most relevant figures for such a system, such as the quantum error bit rate and the estimated secret key versus the link length. The software also includes a post-processing stack which takes the exchanged quantum states and produces shared quantum keys between the two parties. The stack includes all the necessary steps of quantum key distribution systems - estimation of physical parameters, information reconciliation between the parties (implemented in our case as slice-based error correction combined with LDPC codes), and privacy amplification (implemented as Toeplitz algorithm). |
| Type Of Technology | Physical Model/Kit |
| Year Produced | 2023 |
| Impact | The impact of the software is the great insight that enable into the realization of a full quantum key distribution system. Varying the physical parameters enable to simulate the system in different real-use scenarios. It also enable the clear and accurate definition of the requirements for the design of photonics, electronic and microelectronic subcomponents that will constitute the system. |
| Title | Integrated circuit design of an high-speed driver amplifier for optical modulators for continuous-variable quantum key distribution |
| Description | We designed an integrated circuit containing a high-speed optical modulator driver to be used in combination with our custom InP transmitter photonic integrated circuit. These will be the core of our continuous-variable quantum key distribution transmitter device. The IC was design in the IHP SiGe13G2 technology, the post-layout simulation suggest a 20 dB gain and 10 GHz of bandwidth. The amplifier has a low noise figure of 2.8 dB and maximum output voltage of 4 Vpeak-peak. These parameters were chosen to be the ideal interface between an high-speed digital-to-analog-converter and an InP high-speed optical modulator. The device will be received in June 2024 for experimental validation. |
| Type Of Technology | Systems, Materials & Instrumental Engineering |
| Year Produced | 2023 |
| Impact | In combination with our InP chip, this IC will contribute to the demonstration of a miniaturized, high-spec continuous-variable quantum key distribution system. |
| Title | Integrated circuit design of an ultra-high performance transimpedance amplifier for continuous-variable quantum information technologies |
| Description | The technical product is the integrated circuit design of a ultra-high performance transimpedance amplifier. Transimpedance amplifiers (TIAs) are at the core of optical communication receivers, including those used for continuous-variable quantum key distribution systems and quantum random number generators. The TIAs used for quantum technologies require levels of sensitivity substantially higher than those used in classical communications, with bandwidth requirements often less stringent than their classical counterpart. Our simulated design suggests an improved sensitivity by a factor >2, by maintaining very competitive bandwidths. This is achieved by using a high-performance BiCMOS integrated circuit platform (IHP SG13G2) and using IC topologies targeted at low-noise applications. |
| Type Of Technology | Systems, Materials & Instrumental Engineering |
| Year Produced | 2023 |
| Impact | The potential impact of this work is to enable the realization state of the art continuous-variable quantum key distribution systems and quantum random number generators, with ultra-low form factor and high-bandwidth. The use of bespoke IC circuits enables to overcome the limitations given by commercially available solutions. |
| Title | Model of a co-integrated photonic integrated circuits and single photon avalanche detectors |
| Description | I developed a new photonic integrated circuit to be co-integrated with single photon avalanche detector. The photonic integrated circuit is designed also to be polarization insensitive. |
| Type Of Technology | New/Improved Technique/Technology |
| Year Produced | 2025 |
| Impact | These two aspects will enable a transformative solution for quantum key distribution systems in the discrete-variable framework. They will remove the last remaining barriers for cheaper and simpler volume scale manufacturing of quantum key distribution systems. At the moment the photonic integrated circuits has been designed. It will be manufactured between April and August and the system will be assembled in Autumn 2025 |
| Title | New technique to produce uniformly distributed quantum random numbers (WP1) |
| Description | One of the limitations of high-performance quantum random number generators is that the produced samples are normally distributed. This limits the number of bits that can be used for cryptographic applications. We have devised a new technique and a new component to produce uniformly distributed quantum random numbers. This has been achieved by designing a novel opto-electronic component and an associated methodology to operate it. The new component can be used for any quantum random number generator that measures an analogue signal, whether it is a voltage or a current. This type of component could be used in technologies quantum and classical, beyond quantum random number generators. A patent is currently under draft and it will be soon filed. |
| Type Of Technology | New/Improved Technique/Technology |
| Year Produced | 2024 |
| Impact | This will help optimize the operation of quantum random number generators and therefore contributed to their use in various fields of application. |
| Title | Optically self-contained quantum random number generator chip (WP1) |
| Description | This product describes (two variant of) a fully optically self-contained quantum random number generator on an InP photonic chip. We validated two Indium Phosphide InP chips which contains all the opto-electronic components (lasers, beam-splitters, modulators, and photodiodes) necessary to produce quantum random numbers based on homodyne measurements of optical quantum vacuum states. The two variants contained different type of opto-electronic components available as part of the process design kit of the chosen manufacturing foundry. Both variants demonstrated ability to produce provable quantum random numbers up to 5 Gbps, and they were packaged inside industry standard QFN packages of 5x5mm^2 area. We have hence developed extensive knowledge of the components available, which will be valuable for quantum random number generators as well as other devices based on the same technology. |
| Type Of Technology | Systems, Materials & Instrumental Engineering |
| Year Produced | 2023 |
| Impact | A fully optically self-contained quantum random number generator has significant impacts in terms of SWaP (size, weight, and power) and costs. Alternative technologies, such as Silicon-on-Insulator, cannot integrate lasers. This means that quantum random number generators made on Silicon-on-Insulator need to have a laser attached or light coupled into the chip through optical fibres. This process has obvious downsides: 1) There are additional manufacturing steps which significantly increase the costs; 2) The need for coupling light into the chip means that the system is more expensive, because of the need of an external laser; 3) The need for an external laser means that the overall size of the system is increased. The full integration of optical components on a single device means that all these issue are solved. The cost/chip in the 10s unit is reduced by more than 70% (the cost of fibre attach of laser to the chip). The self-contained device can be assembled by standard companies. This has thus the direct impact of lowering the cost of the full quantum random number generator device. |
| Title | Photonic Integrated Circuit Design for high-performance Continuous-variable quantum key distribution systems |
| Description | The photonic integrated circuits (PICs) are three main building blocks for a low-form factor, high-performance quantum key distribution system. These are designed in a highly integrated photonic platform (HHI, Indium Phosphide). The building blocks designed are the following: - a transmitter device: it includes high-bandwidth electro-optic modulators, variable optical attenuators, laser sources and photodiodes to produce coherent optical quantum states at high-rates; - a receiver device: it includes balanced detectors to detect coherent optical quantum states; - a quantum random number generator: it includes laser source and balanced detectors. |
| Type Of Technology | Systems, Materials & Instrumental Engineering |
| Year Produced | 2022 |
| Impact | Combined with the transimpedance amplifier (already part of this portfolio), and further components that will be designed in the future, these PICs will be a fundamental building block for the low form factor, high-performance continuous-variable quantum key distribution system, which is one of the proposed objective of this Fellowship. The use of integrated circuits, photonics and electronics, provide a combined benefits of form factor, performance and manufacture scalability that are impossible otherwise. The potential impact of these components is therefore the significant simplification and cost reduction of quantum cryptography devices. |
| Title | Validation of InP receiver photonic integrated circuit for continuous-variable quantum key distribution system (WP2) |
| Description | Here we describe an opto-electronic system used as a receiver for a continuous-variable quantum key distribution system (CV-QKD). The optical part of this is built on an InP photonic integrated circuit. The electronics is based on high-performance surface mount components available on the market. The system was able to perform the fundamental measurements to be suitable as receiver for (CV-QKD). 1) The main requirement for a CV-QKD is to be able to clearly distinguish between optical quantum noise and other sources of noise. Our device was able to show a clear 10 dB clearance between quantum noise and classical noise. 2) Another critical requirement is to achieve sufficiently high bandwidth that will enable the system to operate at sufficient speeds. Our device showed a bandwidth of 1GHz, which is comparable to high-performance systems demonstrated in the recent literature. 3)A third critical feature is a sufficiently narrow linewidth and stable laser. We measured a laser linewidth of around 1 MHz, in agreement with the foundry specifications. We were also able to demonstrate stable interference between this on-chip receiver laser (called local oscillator) and different types of external lasers. This is a critical milestone needed to demonstrate the feasibility of a InP-based CV-QKD systems with on-chip signal and local oscillator lasers. |
| Type Of Technology | Systems, Materials & Instrumental Engineering |
| Year Produced | 2024 |
| Impact | We expect that these results could pave the way to fully integrated chip-based CV-QKD system, hence have a significant impact in the cost reduction and hence widespread use of quantum key distribution. This will be fully possible once the complementary transmitter will be fully validated. |
| Description | KETS ar Quantum Optica Industry event |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Industry/Business |
| Results and Impact | I gave an invited talk at an industrial summit event titled "Quantum Industry Summit" organized by Optica |
| Year(s) Of Engagement Activity | 2024 |
| URL | https://www.optica.org/events/industry_events/2024/optica_2024_quantum_industry_summit_-_third_editi... |
| Description | Scaling the Edge Programme |
| Form Of Engagement Activity | Participation in an activity, workshop or similar |
| Part Of Official Scheme? | No |
| Geographic Reach | National |
| Primary Audience | Industry/Business |
| Results and Impact | I am taking part to the Scaling the Edge Programme proposed to the Future Leaders Fellows based in UK business. The motivation behind my attendance to the programme is to perform a market discovery of the technology I am developing as part of one of the work packages. This is in line with the vision of my Fellowship to help the widespread use of quantum technologies. After 3 days of introductory bootcamp, I have been supported by a coach in the exploration of new potential application throughout the course of 10 weeks. I have spoken with industry professionals and academics to understand the suitability of my technology for their specific needs. In doing this I have also attended, as a visitor, the Tech Show London, where vendors and companies in relevant fields gathered in March |
| Year(s) Of Engagement Activity | 2023 |