arXiv subjects

Albert Williams

Publications and source records attributed to Albert Williams.

4 recordsLinked to original sources

arXiv2026

Designing a Satellite Serviced Quantum Network Backbone for Concurrent Global Connectivity

Satellite-serviced quantum networks pose an architectural problem distinct from classical satellite networking: because entanglement cannot be copied, and long-lived buffering is technologically constrained for near-term devices, useful end-to-end service requires fixed optical ground infrastructure and simultaneous multi-hop path availability. We investigate the design of a satellite-serviced quantum backbone aimed at supporting concurrent global connectivity across a traffic matrix of major population and financial centers under finite waiting-time constraints. Using a discrete-time simulator, we evaluate performance using two architecture-level metrics: (i) time-to-connectivity, and (ii) latency-conditioned average active-link strength. Across a broad parameter sweep, we identify three dominant architectural effects. First, anisotropic ground-station lattices reduce time-to-connectivity relative to longitudinally collapsed and isotropic baselines by aligning ground infrastructure with latitude-dependent satellite access. Second, multi-inclination LEO constellations reduce waiting times for strong connectivity compared to single-inclination constellations at fixed satellite budgets by providing additional visibility for a diverse latitude set. Third, multi-party satellite service policies alleviate per-satellite concurrency bottlenecks and substantially reduce time-to-connectivity at stringent traffic-matrix thresholds. We further show that satellite altitude is the dominant physical lever shaping the visibility--loss trade-off, strongly affecting both connectivity latency and achievable link strength, while orbital plane count and satellite packing provide secondary refinements at fixed altitude. Together, these results delineate the architectural conditions required for scalable, concurrent entanglement connectivity in satellite-serviced quantum networks.

quant-ph↗

arXiv2026

Optimizing Orbital Parameters of Satellites for a Global Quantum Network

Due to fundamental limitations on terrestrial quantum links, satellites have received considerable attention for their potential as entanglement generation sources in a global quantum internet. In this work, we focus on the problem of designing a constellation of satellites for such a quantum network. We find satellite inclination angles and satellite cluster allocations to achieve maximal entanglement generation rates to fixed sets of globally distributed ground stations. Exploring two black-box optimization frameworks: a Bayesian Optimization (BO) approach and a Genetic Algorithm (GA) approach, we find comparable results, indicating their effectiveness for this optimization task. While GA and BO often perform remarkably similar, BO often converges more efficiently, while later growth noted in GAs is indicative of less susceptibility towards local maxima. In either case, they offer substantial improvements over naive approaches that maximize coverage with respect to ground station placement.

quant-ph↗

arXiv2025

Multi-Mode Quantum Memories for High-Throughput Satellite Entanglement Distribution

Quantum networking seeks to enable global entanglement distribution through terrestrial and free space channels; however, the exponential loss in these channels necessitates quantum repeaters with efficient, long lived quantum memories (QMs). Space based architectures, particularly satellite assisted links, offer a path to truly global connectivity, yet they demand QMs that are compatible with orbital factors such as infrared radiation and the unique challenges of operating aboard a satellite. In this work, we propose a multimode quantum memory (MMQM) for low Earth orbit (LEO) repeaters based on the atomic frequency comb (AFC) protocol. Our design integrates a hybrid alkali noble gas ensemble in an optical cavity, using alkali atoms for strong photon matter coupling and noble gas nuclear spins for minutes to hours coherence, all without the need for cryogenics. The architecture natively supports temporal and spectral multiplexing, enabling the storage of 100 modes to parallelize probabilistic operations and overcome light limited round trip times. Representative link budgets at $h = 500$ km with realistic apertures, $\eta_{\text{mem}}\gtrsim 70%$, and $t_{\text{buffer}}$ of several minutes predict improvements of up to two orders of magnitude in per pass success probability and instantaneous SKR relative to a memoryless dual downlink, with clear scaling in $N$. Our contributions are (i) a non cryogenic, space ready multimode memory, (ii) a systems analysis coupling mode count, storage time, and orbital geometry to achievable rate, and (iii) a near term implementation roadmap. Together, these results indicate feasibility with current to near term technology and provide a practical path toward a high rate, space enabled quantum internet.

quant-ph↗

arXiv2024

Scalable Scheduling Policies for Quantum Satellite Networks

As Low Earth Orbit (LEO) satellite mega constellations continue to be deployed for satellite internet and recent successful experiments in satellite-based quantum entanglement distribution emerge, a natural question arises: How should we coordinate transmissions and design scalable scheduling policies for a quantum satellite internet? In this work, we consider the problem of transmission scheduling in quantum satellite networks subject to resource constraints at the satellites and ground stations. We show that the most general problem of assigning satellites to ground station pairs for entanglement distribution is NP-hard. We then propose four heuristic algorithms and evaluate their performance for Starlink mega constellation under various amount of resources and placements of the ground stations. We find that the maximum number of receivers necessary per ground station grows very slowly with the total number of deployed ground stations. Our proposed algorithms, leveraging optimal weighted b-matching and the global greedy heuristic, outperform others in entanglement distribution rate, entanglement fidelity, and handover cost metrics. While we develop these scheduling algorithms, we have also designed a software system to simulate, visualize, and evaluate satellite mega-constellations for entanglement distribution.

quant-ph↗