This paper presents an in-depth satellite-to-ground Quantum Key Distribution (QKD) feasibility analysis between a Low Earth Orbit (LEO) satellite and a 0.28 m small-sized Optical Ground Stations (OGSs) located in urban areas, over nighttime. Both Prepare & Measure (P&M) and Entanglement (ENT)- based QKD protocols are employed and compared in terms of distilled key bits. The performance of various detection setups and environmental conditions including different wavelengths (1550 nm and 810 nm) as well as different types of detectors (Avalanche and Superconducting Nanowires) is simulated. The results are compared to those obtained when OGSs with much larger receiver apertures are placed in rural environment. Our analysis delivers a framework examining the parameters affecting the QKD satellite downlink, and also provides a thorough theoretical framework for the employment of small-sized OGSs in urban environments.
This paper presents an in-depth satellite-to-ground Quantum Key Distribution (QKD) feasibility analysis between a Low Earth Orbit (LEO) satellite and a 0.28 m small-sized Optical Ground Stations (OGSs) located in urban areas, over nighttime. Both Prepare & Measure (P&M) and Entanglement (ENT)- based QKD protocols are employed and compared in terms of distilled key bits. The performance of various detection setups and environmental conditions including different wavelengths (1550 nm and 810 nm) as well as different types of detectors (Avalanche and Superconducting Nanowires) is simulated. The results are compared to those obtained when OGSs with much larger receiver apertures are placed in rural environment. Our analysis delivers a framework examining the parameters affecting the QKD satellite downlink, and also provides a thorough theoretical framework for the employment of small-sized OGSs in urban environments.
As Quantum Key Distribution (QKD) seems to turn towards satellite communication infrastructure to interconnect distant nodes aiming to a global quantum secured network, the number of assisting satellites is expected to increase. In this work, a feasibility analysis of a large-scale Low Earth Orbit (LEO) satellite constellation supporting LEO to ground QKD links is presented. A software tool to simulate the physical properties of a large-scale satellite constellation and a link budget calculator tailored for LEO satellite to ground QKD links have been developed. A large-scale LEO satellite constellation with 100 satellites orbiting at 550km altitude with 53deg inclination angle in ten different orbital planes (10 satellites per orbital plane) has been simulated and subsatellite points for 1 year have been obtained. Assuming, an optical ground station network consisting of nine different optical ground stations located in observatories across Europe, the performance of this large-scale constellation is evaluated in terms of availability and Secure Key Rate (SKR) employing the prepare and measure Decoy-State BB84 QKD protocol, during nighttime, under different atmospheric conditions including cloud coverage and turbulence effects among others, while two different wavelengths (i.e., 800nm and 1550nm) are examined. For each Optical Ground Station (OGS) location, Gbits of distilled keys per year per ground station and key rates up to Kbps are reported.
Optical quantum communication utilizing satellite platforms has the potential to extend the reach of quantum key distribution (QKD) from terrestrial limits of ∼200 km to global scales. We have developed a thorough numerical simulation using realistic simulated orbits and incorporating the effects of pointing error, diffraction, atmosphere and telescope design, to obtain estimates of the loss and background noise which a satellite-based system would experience. Combining with quantum optics simulations of sources and detection, we determine the length of secure key for QKD, as well as entanglement visibility and achievable distances for fundamental experiments. We analyse the performance of a low Earth orbit satellite for downlink and uplink scenarios of the quantum optical signals. We argue that the advantages of locating the quantum source on the ground justify a greater scientific interest in an uplink as compared to a downlink. An uplink with a ground transmitter of at least 25 cm diameter and a 30 cm receiver telescope on the satellite could be used to successfully perform QKD multiple times per week with either an entangled photon source or with a weak coherent pulse source, as well as perform long-distance Bell tests and quantum teleportation. Our model helps to resolve important design considerations such as operating wavelength, type and specifications of sources and detectors, telescope designs, specific orbits and ground station locations, in view of anticipated overall system performance.
Quantum key distribution (QKD) has gained a lot of attention over the past few years, but the implementation of quantum security applications is still challenging to accomplish with the current technology. Towards a global-scale quantum-secured network, satellite communications seem to be a promising candidate to successfully support the quantum communication infrastructure (QCI) by delivering quantum keys to optical ground terminals. In this research, we examined the feasibility of satellite-to-ground QKD under daylight and nighttime conditions using the decoy-state BB84 QKD protocol. We evaluated its performance on a hypothetical constellation with 10 satellites in sun-synchronous Low Earth Orbit (LEO) that are assumed to communicate over a period of one year with three optical ground stations (OGSs) located in Greece. By taking into account the atmospheric effects of turbulence as well as the background solar radiance, we showed that positive normalized secure key rates (SKRs) up to 3.9×10−4 (bps/pulse) can be obtained, which implies that satellite-to-ground QKD can be feasible for various conditions, under realistic assumptions in an existing infrastructure.
This paper presents a comprehensive feasibility analysis designed to model Low Earth Orbit (LEO) satellite-to-ground communications for Quantum Key Distribution (QKD), focusing on the 1550nm wavelength to facilitate the distribution of information through fiber segments. Discrete Variable Decoy State Polarization-based BB84 protocol is assumed whereas various detection setups and environmental conditions are simulated. Our analysis focuses on the receiver's design in terms of aperture and focal length to deliver a general framework by examining the coupling efficiency, a parameter strongly affecting the QKD satellite downlink. Through detailed simulation, we identify optimal configurations and operational parameters for various receiver designs, significantly enhancing the efficiency and reliability of satellite-to-ground QKD systems. The findings offer promising directions for extending the range of QKD systems, potentially revolutionizing secure communications by integrating satellite-transmitted quantum keys with terrestrial fiber networks. This study not only underscores the feasibility of advancing satellite-to-ground QKD technology but also lays the groundwork for future innovations in global quantum communications infrastructure.
Quantum Key Distribution (QKD) is a promising method to guarantee future-proof, information theoretic security. Since optical fibers have an exponential loss with distance, satellite-based QKD solutions are being developed in order to realize long-distance links. Therefore, Optical Ground Stations for QKD (QKD-OGS) need to be designed to enable quantum communication with satellites. Different link configurations will result in different integration options of the QKD-OGS in the terrestrial fiber network and therefore impact its performance. Applicable integration options must be identified and trade-off analysis conducted at the architecture, system and sub-system level. The reference scenario is a Low Earth Orbit (LEO) downlink configuration employing a decoy-state BB84 protocol with polarization encoded qubits at 1550 nm wavelength. The satellite acts as trusted node for implementation of the key distribution between two parties on ground. Furthermore, only direct connections from the satellite to the end-users are considered, i.e. the QKD-OGS does not serve as a trusted-node relay. This results in the selection of three main integration concepts: first, a free-space, end-user QKD-OGS which is located directly at the end-user where the quantum signal is measured directly behind the receiver telescope in free-space; second, a fiber-coupled, end-user QKD-OGS where the quantum signal is coupled into a single-mode fiber and guided to a co-located server room hosting the QKD Receiver system; third, a fiber-coupled, provider QKD-OGS, which reaches several end-users by using a local fiber network. In order to evaluate these three concepts, the comparison parameter is defined to be an estimated factor of suppliable end-users. The estimated comparison factor shows that the fiber-coupled, enduser QKD-OGS can supply 6.7 times more end users than the free-space, end-user QKD-OGS. The fiber-coupled, end-user QKD-OGS can supply 129.7 times more end-users than the free-space, end-user QKD-OGS.
Satellite quantum communications have received a surge of interest in recent years, encouraged by the success of the QUESS experiments and as a reaction to advances in quantum computing. This work focuses on low Earth orbit nanosatellite missions, which offer several benefits (e.g. lower costs, greater launch availability, easier to replenish) over satellites at different orbit heights (medium Earth orbit, geosynchronous Earth orbit) and satellite size classes (e.g. small-sats, etc). Recent work on low Earth orbit satellite Quantum Key Distribution (QKD) has focused on transmitters and quantum sources, with less attention paid to the receiver side of the link. This review addresses that imbalance by focusing on the receiver and detection systems of satellite quantum communications. This work has found that two-way beacon acquisition and tracking systems are both a common element of state-of-the-art missions, and likely to remain a critical subsystem to ensure high-quality satellite-to-ground station links; however, improvements to detection and tracking algorithms could be made. For discrete variable QKD, receivers and detection systems in nanosatellites at low Earth orbit are likely to remain using silicon single photon avalanche diodes, while receivers and detection systems in optical ground stations may opt for superconducting nanowire single photon detectors, as cryogenic cooling is feasible. For continuous variable QKD, the receivers and detection systems, using coherent detection systems, share many hardware elements with classical optical satellite communications. Combined with coherent detection systems’ inherent resilience to operating during daytime conditions, this makes continuous variable QKD an attractive prospect for future missions, if its fundamental challenges can be overcome.