Inter-satellite Quantum Key Distribution at Terahertz Frequencies

Terahertz (THz) communication is a topic of much research in the context of high-capacity next-generation wireless networks. Quantum communication is also a topic of intensive research, most recently in the context of space-based deployments. In this work we explore the use of THz frequencies as a means to achieve quantum communication within a constellation of micro-satellites in Low-Earth-Orbit (LEO). Quantum communication between the micro-satellite constellation and high-altitude terrestrial stations is also investigated. Our work demonstrates that THz quantum entanglement distribution and THz quantum key distribution are viable deployment options in the micro-satellite context. We discuss how such deployment opens up the possibility for simpler integration of global quantum and wireless networks. The possibility of using THz frequencies for quantum-radar applications in the context of LEO deployments is briefly discussed.Comment: 7 pages, 6 figure

Detecting Orbital Angular Momentum of Light in Satellite-to-Ground Quantum Communications

Satellite-based quantum communications enable a bright future for global-scale information security. However, the spin orbital momentum of light, currently used in many mainstream quantum communication systems, only allows for quantum encoding in a two-dimensional Hilbert space. The orbital angular momentum (OAM) of light, on the other hand, enables quantum encoding in higher-dimensional Hilbert spaces, opening up new opportunities for high-capacity quantum communications. Due to its turbulence-induced decoherence effects, however, the atmospheric channel may limit the practical usage of OAM. In order to determine whether OAM is useful for satellite-based quantum communications, we numerically investigate the detection likelihoods for OAM states that traverse satellite-to-ground channels. We show that the use of OAM through such channels is in fact feasible. We use our new results to then investigate design specifications that could improve OAM detection - particularly the use of advanced adaptive optics techniques. Finally, we discuss how our work provides new insights into future implementations of space-based OAM systems within the context of quantum communications.Comment: 7 pages, 7 figure

Advanced Quantum Communications via Satellites

This thesis investigates the feasibility of advanced satellite-based quantum communications utilizing multi-dimensional encoding. Considering the use of satellite-to-Earth and inter-satellite configurations for quantum communications, we explore the use of multiple potential quantum information carriers as a means to enable the benefits of high-dimensional quantum encoding. We establish a realistic channel model to investigate the quantum state evolution within satellite-based quantum channels for each of the considered quantum information carriers, including the orbital angular momentum and the temporal modes of single photons, as well as the quadrature variables of optical fields. Applying our established channel models, we determine, via detailed evaluations including both theoretical analyses and numerical simulations, the performances of various multi-dimensional quantum information protocols utilizing different quantum information carriers for quantum encoding within the context of satellite-based quantum communications. The quantum information protocols we investigate include entanglement distribution, quantum key distribution, and quantum teleportation. For the practical deployment of satellite-based multi-dimensional quantum communications, we compare the performances of each considered quantum information protocol achieved with different quantum information carriers. Considering the fragility of multi-dimensional quantum states in the arduous environment of the Earth’s atmosphere, we further explore the probing of quantum channels and the use of real-time quantum channel information as a means to improve the feasibility and performance of satellite-based multi-dimensional quantum communications. Although not the core contribution of this thesis, we also explore the possibility of the simple integration of global quantum and wireless networks via the use of Terahertz frequencies for quantum communications within the context of micro-satellite constellations. This thesis provides novel and important insights into the development and implementation of advanced satellite-based quantum communications. Such insights should be very useful for the practical realization of a useful global-scale quantum Internet in the future