Quantum Key Distribution utilises fundamental quantum properties and mechanics to generate a cryptographic key, ensuring the highest security regardless of advances to computer processing. AMMEQ-1 is a 3U cubesat being developed by The University of Sydney, Australia hosting a primary payload provided by Centre for Quantum Technologies, Singapore. Its main purpose is to show USYD's capability of developing a satellite using COTS products and to demonstrate various technologies to support future QKD missions. This study describes the mission and overall system design of the cubesat.
Quantum Key Distribution utilises fundamental quantum properties and mechanics to generate a cryptographic key, ensuring the highest security regardless of advances to computer processing. AMMEQ-1 is a 3U cubesat being developed by The University of Sydney, Australia hosting a primary payload provided by Centre for Quantum Technologies, Singapore. Its main purpose is to show USYD's capability of developing a satellite using COTS products and to demonstrate various technologies to support future QKD missions. This study describes the mission and overall system design of the cubesat.
Quantum Key Distribution (QKD) is a technology that can distribute private encryption keys between two parties with strong security assurances underpinned by quantum mechanics. Entanglement-based QKD is one of the strongest forms of QKD. Performing QKD using satellites can overcome the range constraints of ground-based QKD systems imposed by atmospheric losses or attenuation in optical fibers. In 2017, satellite-based QKD has been demonstrated by the Chinese Academy of Sciences’ 630kg Micius satellite. Independently in Singapore we are developing similar, but greatly more compact QKD technologies targeted at CubeSats. Our first on-orbit demonstration of a simple quantum light source was in 2016 on board the Galassia 2U CubeSat. Next on the pad, our SpooQy-1 CubeSat is a 3U GomSpace platform built at CQT that aims to validate the space-worthiness of our next generation entangled photon light source and demonstrate a radio beacon of quantum random numbers. In future missions our miniaturized entangled photon light sources can be combined with high precision Pointing, Acquisition and Tracking System (PATS) and optical communication links to enable a global QKD network with small satellites.
Quantum Key Distribution (QKD) offers a fundamentally secure method for key exchange, grounded in the principles of quantum mechanics rather than computational complexity. As advancements in quantum computing threaten classical cryptographic systems (such as RSA) QKD presents itself as a crucial technology for future secure communications. Among the primary challenges for global-scale QKD is the limited range of optical fiber channels, making satellite-based free-space optical links an attractive alternative. QKD presents unique constraints related to the short and unreliable communication windows, due to atmospheric conditions and the presence of sunlight, which makes the real time operation of QKD constellations almost impossible. Traditional configurations offering instantaneous global coverage, such as Walker constellations, are not necessary for QKD networks and other constellation designs may be explored. In this work, we present as an alternative a two-height, single orbital plane constellation, which facilitates regular and extended inter-satellite visibility, enabling the constellation to function as a virtual trusted node and increasing network capacity and flexibility. The main technical contribution is the development of a simulation tool designed to evaluate and optimize satellite QKD constellations. The simulator allows researchers and mission planners to assess key generation rates and overall system performance, helping to reduce the risks, costs, and uncertainties involved in satellite deployment. Our approach provides a powerful framework for advancing the development of scalable and efficient global QKD networks.
Quantum key distribution (QKD), a novel cryptographic technique for secure distribution of secret keys between two parties, is the first successful quantum technology to emerge from quantum information science. The security of QKD is guaranteed by fundamental properties of quantum mechanical systems, unlike public-key cryptography whose security depends on difficult to solve mathematical problems such as factoring. Current terrestrial quantum links are limited to about 250 km. However, QKD could soon be deployed on a global scale over free-space links to an orbiting satellite used as a trusted node. \n \nEnvisioning a photonic uplink to a quantum receiver positioned on a low Earth orbit satellite, the Canadian Quantum Encryption and Science Satellite (QEYSSat) is a collaborative project involving Canadian universities, the Canadian Space Agency (CSA) and industry partners. This thesis presents some of the research conducted towards feasibility studies of the QEYSSat mission. \n \nOne of the main goals of this research is to develop technologies for data acquisition and processing required for a satellite-based QKD system. A working testbed system helps to establish firmly grounded estimates of the overall complexity, the computing resources necessary, and the bandwidth requirements of the classical communication channel. It can also serve as a good foundation for the design and development of a future payload computer onboard QEYSSat. \n \nThis thesis describes the design and implementation of a QKD post-processing system which aims to minimize the computing requirements at one side of the link, unlike most traditional implementations which assume symmetric computing resources at each end. The post-processing software features precise coincidence analysis, error correction based on low-density parity-check codes, privacy amplification employing Toeplitz hash functions, and a procedure for automated polarization alignment. \n \nThe system's hardware and software components integrate fully with a quantum optical apparatus used to demonstrate the feasibility of QKD with a satellite uplink. Detailed computing resource requirements and QKD results from the operation of the entire system at high-loss regimes are presented here.
In a world of global satellite communication networks, it is crucial to ensure the security of these data links. QUBE is a project that will develop and launch a CubeSat for the downlink of strongly attenuated light pulses, with encoded quantum information, which can be used for the exchange of encryption keys. This 3U Pico-Satellite will be built using the UNISEC-Europe standard, which has been proven to provide a robust framework for increased reliability for CubeSat missions. In addition to advanced reaction wheels for precision pointing, the satellite will be carrying the DLR-OSIRIS optical downlink system as well as dedicated payloads for testing components required for quantum key distribution. A miniaturized quantum random number generator (QRNG) will create a sequence of numbers, which can be used to set the quantum states of the light. The light pulses will then be downlinked to the optical ground station at DLR in Oberpfaffenhofen, Germany, which is equipped with the corresponding components for receiving the quantum states. Additionally, the random numbers will partially be made available via an RF downlink. This will allow evaluating the link loss as well as the noise and errors in the transmission of quantum signals. In QKD, due to the underlying quantum mechanics, any attempt of reading the quantum states will alter them, which makes interceptions easily detectable. The quantum communication experiments will evaluate whether secure communication links are possible even on a CubeSat scale. A major challenge for building the required CubeSat is the attitude determination and control system that will provide precise pointing. This work will outline detailed mission requirements as well as the chosen subsystems for tackling these challenges in order to deliver a successful mission.
Satellite nodes are an enabler of global quantum networks by overcoming the distance limitations of fiber and free-space links on ground. The design of quantum sources and receivers for satellites, however, is challenging in terms of size, weight, and power consumption, as well as mechanical and thermal stability. This is all the more true for cost-efficient nanosatellites such as the popular CubeSat platform standard. Here we report on the follow-up mission of SpooQy-1, a 3U CubeSat that successfully demonstrated the generation of polarization-entangled photons in orbit. The next iteration of the mission will showcase satellite-to-ground quantum key distribution based on a compact source of polarization-entangled photon-pairs, and we have recently completed the integration of a fully functional demonstrator as a milestone towards the flight model. We also briefly describe the design of the optical ground station that we are currently building in Singapore for receiving the quantum signal. We present the most important subsystems and illustrate the concept of operation.
The QUBE-I mission is a technology demonstrator mission for novel building-blocks for satellite-based quantum-key-distribution (QKD). The mission aims to test three highly integrated optical payloads, a quantum random number generator and two transmitters for polarization and phase encoded quantum states as a precursor mission for the first QKD demonstration from a CubeSat. The QKD sources are connected to, and are integrated together with the Optical Space Infrared Downlink System (OSIRIS) for QUBE (O4Q) in a 3U CubeSat. One of the mission's primary challenges is achieving a precise and accurate pointing of the O4Q with an error margin of less than 1° towards the optical ground station (OGS). Additionally, conducting the experiments presents several operational challenges, such as the need for precise orbital elements to track the satellite with the OGS and safety mechanisms to protect the Sunsensitive components of the satellite. Following the launch on 16th August 2024, we conducted an extensive commissioning phase to test all subsystems, payload components, and operational procedures. This paper provides insights and results from QUBE-I's first year in orbit, highlighting lessons learned from integrating multiple complex payload systems into a 3U CubeSat platform. Starting with communication establishment, we present the ground segment and operations capabilities. We elaborate on the use of flexible on-board scripting and recording mechanisms provided by the satellite's flight software stack for operations. An effective review, test, and deployment procedure was established to balance risk mitigation and agile operation planning. We present results of extensive tests conducted for the crucial attitude determination and control system (ADCS), including actuator verification, spin-up and detumbling tests, in-orbit sensor calibration procedures, and the evaluation of various pointing modes, such as the fine pointing mode required for the experiments. Besides that, we give insights in the actual performance of the experimental and scientific payloads after their commissioning. A big milestone marked the successful test of the operational procedure for the QKD experiments. This includes the timely provision of precise orbit determination to the OGS for tracking. In addition, the ADCS needs to prepare the fine pointing mode accordingly and the experiment needs to be started autonomously before actual contact. Flexibly selectable on-board recordings can be downloaded after the experiments for evaluation. As expected, the technical complexity of the QUBE-I mission resulted in a challenging first year of operation. With this paper, we aim to share our experiences and contribute our insights to the space community.