Philosophical Transactions of the Royal Society A Mathematical Physical and Engineering Sciences
Exploring the boundaries of quantum mechanics: advances in satellite quantum communications
Costantino Agnesi, Francesco Vedovato, Matteo Schiavon, Daniele Dequal, Luca Calderaro, Marco Tomasin, Davide G. Marangon, Andrea Stanco, V. Luceri, G. Bianco, Giuseppe Vallone, Paolo Villoresi
Recent interest in quantum communications has stimulated great technological progress in satellite quantum technologies. These advances have rendered the aforesaid technologies mature enough to support the realization of experiments that test the foundations of quantum theory at unprecedented scales and in the unexplored space environment. Such experiments, in fact, could explore the boundaries of quantum theory and may provide new insights to investigate phenomena where gravity affects quantum objects. Here, we review recent results in satellite quantum communications and discuss possible phenomena that could be observable with current technologies. Furthermore, stressing the fact that space represents an incredible resource to realize new experiments aimed at highlighting some physical effects, we challenge the community to propose new experiments that unveil the interplay between quantum mechanics and gravity that could be realizable in the near future.This article is part of a discussion meeting issue 'Foundations of quantum mechanics and their impact on contemporary society'.
Recent interest in quantum communications has stimulated great technological progress in satellite quantum technologies. These advances have rendered the aforesaid technologies mature enough to support the realization of experiments that test the foundations of quantum theory at unprecedented scales and in the unexplored space environment. Such experiments, in fact, could explore the boundaries of quantum theory and may provide new insights to investigate phenomena where gravity affects quantum objects. Here, we review recent results in satellite quantum communications and discuss possible phenomena that could be observable with current technologies. Furthermore, stressing the fact that space represents an incredible resource to realize new experiments aimed at highlighting some physical effects, we challenge the community to propose new experiments that unveil the interplay between quantum mechanics and gravity that could be realizable in the near future.This article is part of a discussion meeting issue 'Foundations of quantum mechanics and their impact on contemporary society'.
Quantum physics has transitioned from a purely theoretical discipline to a transformative technological foundation influencing modern space science and engineering. From ultra-precise atomic clocks enabling global navigation systems to quantum sensors enhancing spacecraft navigation and quantum communication networks promising unbreakable encryption, quantum mechanics now plays a pivotal role in space technology. This research paper explores the theoretical foundations of quantum physics and examines its applications in satellite systems, deep-space exploration, communication networks, gravitational sensing, propulsion research, and cosmology. It further discusses current missions led by agencies such as NASA, European Space Agency, and China National Space Administration, highlighting advancements in space-based quantum experiments. The paper concludes with future prospects, technical challenges, and the role of quantum technology in shaping next-generation space exploration.
Satellite-based quantum communications represent a critical advancement in the pursuit of secure, global-scale quantum networks. Leveraging the principles of quantum mechanics, these systems offer unparalleled security through Quantum Key Distribution (QKD) and other quantum communication protocols. This review provides a comprehensive overview of the current state of satellite-based quantum communications, focusing on the evolution from terrestrial to space-based systems. We explore the distinct advantages and challenges of discrete-variable (DV) and continuous-variable (CV) quantum communication technologies in the context of satellite deployments. The paper also discusses key milestones such as the successful implementation of quantum communication via the Micius satellite and outlines the primary challenges, including atmospheric turbulence and the development of quantum repeaters, that must be addressed to achieve a global quantum internet. This review aims to consolidate recent advancements in the field, providing insights and perspectives on the future directions and potential innovations that will drive the continued evolution of satellite-based quantum communications.
The foundations of quantum mechanics have been a subject of intense investigation and debate since the theory's inception. Recent developments in quantum technologies and theoretical frameworks have shed new light on foundational issues and raised intriguing questions about the nature of reality at the quantum level. recent advancements in our understanding of the foundational principles of quantum mechanics and discuss unresolved questions that continue to challenge our conceptual framework. Topics of interest include the measurement problem, quantum entanglement, the role of contextuality and nonlocality, interpretations of quantum theory, and the quest for a unified theory of quantum gravity. findings and ongoing debates in the field, we aim to provide a comprehensive overview of the current state of research in the foundations of quantum mechanics and stimulate further discussion and inquiry into these fundamental questions.
Quantum satellite communication (QSC) is emerging as a strategic technology for secure global networking and long-distance quantum connectivity. This review prioritizes the major challenges that still hinder large-scale deployment, including atmospheric loss, beam pointing and tracking, payload constraints, synchronization, scalability, and integration with terrestrial infrastructure. To contextualize these issues, we provide only a concise overview of the core concepts and enabling technologies behind QSC, together with representative milestones such as the Micius mission. Building on this background, the paper surveys recent advances in protocols, hybrid space--terrestrial architectures, turbulence mitigation, and AI-assisted optimization. It then examines future directions, including quantum Internet integration, daylight operation, satellite-supported repeaters, and space-based quantum computing. By centering the discussion on open technical bottlenecks and emerging research trajectories, this review aims to support researchers and engineers working toward practical and resilient QSC systems.
From the very beginning, Quantum Mechanics has been accompanied by crucial foundational questions: the possibility of visualizing physical processes, the limits of measurement epitomized by the Heisenberg uncertainty principle, the existence of a deeper underlying reality with additional degrees of freedom, the role of measurements, and the status of locality. Long regarded as philosophical speculations, these issues were progressively reformulated into precise mathematical statements and ultimately subjected to experimental verification. The trajectory proved unpredictable: questions once dismissed as metaphysical gave rise to experimental platforms, which in turn matured into devices and technologies powering quantum computation, communication, and sensing. Yet this development is not unidirectional: advances in technology also feed back into foundations, enabling tests of principles that were previously out of reach, for example, whether quantum superposition persists at larger and larger scales and whether reality, gravity included, is fundamentally quantum. In this way, the dialogue between foundational inquiry and technological progress continues to shape both our theoretical understanding and the practical realization of quantum phenomena.
Nearing a century since its inception, quantum mechanics is as lively as ever. Its signature manifestations, such as superposition, wave-particle duality, uncertainty principle, entanglement and nonlocality, were long confronted as weird predictions of an incomplete theory, paradoxes only suitable for philosophical discussions, or mere mathematical artifacts with no counterpart in the physical reality. Nevertheless, decades of progress in the experimental verification and control of quantum systems have routinely proven detractors wrong. While fundamental questions still remain wide open on the foundations and interpretations of quantum mechanics, its modern technological applications have captured the fascination of the general public and are having a transformative impact on society. This brief article acts as Introduction to a Special Issue in the Philosophical Transactions of Royal Society A, following from a dedicated Scientific Discussion Meeting where these fascinating topics were explored, giving rise to stimulating debates among speakers and audience. The present issue thus aims at conveying the spirit of those discussions.