The secure communication of information plays an ever increasing role in our society today. Classical methods of encryption inherently rely on the difficulty of solving a problem such as finding prime factors of large numbers and can, in principle, be cracked by a fast enough machine. The burgeoning field of quantum communication relies on the fundamental laws of physics to offer unconditional information security. Here we introduce the key concepts of quantum superposition and entanglement as well as the no-cloning theorem that form the basis of this field. Then, we review basic quantum communication schemes with single and entangled photons and discuss recent experimental progress in ground and space-based quantum communication. Finally, we discuss the emerging field of high-dimensional quantum communication, which promises increased data rates and higher levels of security than ever before. We discuss recent experiments that use the orbital angular momentum of photons for sharing large amounts of information in a secure fashion. These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.
The secure communication of information plays an ever increasing role in our society today. Classical methods of encryption inherently rely on the difficulty of solving a problem such as finding prime factors of large numbers and can, in principle, be cracked by a fast enough machine. The burgeoning field of quantum communication relies on the fundamental laws of physics to offer unconditional information security. Here we introduce the key concepts of quantum superposition and entanglement as well as the no-cloning theorem that form the basis of this field. Then, we review basic quantum communication schemes with single and entangled photons and discuss recent experimental progress in ground and space-based quantum communication. Finally, we discuss the emerging field of high-dimensional quantum communication, which promises increased data rates and higher levels of security than ever before. We discuss recent experiments that use the orbital angular momentum of photons for sharing large amounts of information in a secure fashion. These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.
This paper presents a comprehensive review of quantum communication using photons, based primarily on the foundational work of Krenn, Malik, Scheidl, Ursin, and Zeilinger. The review covers core quantum mechanical principles such as qubits, superposition, entanglement, and the no-cloning theorem, and explains how these principles underpin secure quantum communication. Key protocols including Quantum Key Distribution (QKD) and quantum teleportation are discussed. The paper further explores long-distance ground-based and space-based experiments, and examines the emerging role of high-dimensional quantum states using Orbital Angular Momentum (OAM) of photons. The aim is to provide a structured understanding of the current state and future potential of quantum communication technologies.
Recent progress in quantum technologies has brought quantum communication and networking from a largely theoretical idea to an emerging practical reality. By exploiting fundamental quantum phenomena such as superposition and entanglement, quantum communication promises capabilities that are fundamentally different and out of reach for classical communication systems, particularly in terms of security and information sharing. This review aims to present the essential theoretical concepts required to understand quantum communication, alongside an experimental and engineering perspective that highlights how these ideas are realized using real hardware. We explain core principles and protocols in a manner that connects the physics to practical system design, allowing readers to see how quantum theory and communication technology jointly enable quantum networking. The paper further surveys recent experimental and technological advances that have made practical quantum communication possible, emphasizing the role of photonic hardware, sources, detectors, and integrated platforms in enabling key operations, now leading to deployment of multi-node long-distance quantum networks. Finally, we also present the current developments in quantum-secure communication and quantum networking efforts undergoing in India, placing them in the context of the global progress.
The rapid advancement of quantum computing poses a significant threat to classical cryptographic systems that rely on the computational hardness of mathematical problems such as integer factorization and discrete logarithm problems. In this context, quantum cryptography has emerged as a promising paradigm for secure communication based on the fundamental principles of quantum mechanics rather than on computational assumptions. This paper presents a comprehensive review of quantum cryptography, with a particular focus on Quantum Key Distribution (QKD), the most mature application. The study discusses the theoretical foundations of quantum security, including superposition, entanglement, and the No-cloning theorem, which collectively enable eavesdropping detection and guarantee information-theoretic security. Furthermore, the review examines major QKD protocols, such as BB84 and E91, as well as their advanced variants designed to address practical vulnerabilities and enhance performance. Recent progress in real-world implementations, including fiber-optic networks, free-space communication, and satellite-based systems such as the Micius satellite, is also analyzed. In addition, the paper highlights critical challenges related to scalability, hardware limitations, and security loopholes arising from imperfect devices. Finally, emerging research directions, including hybrid cryptographic frameworks that integrate quantum and post-quantum approaches, are discussed to provide insights into the future of secure communication. This review aims to provide a structured, up-to-date understanding of quantum cryptography, bridging the gap between theoretical developments and practical implementations, and emphasizing its crucial role in shaping next-generation cybersecurity systems.
Dramatic paradigm shifts over the past few centuries have led to a rich landscape of options in human and machine communication. Communication today is deeply intertwined with our personal and social lives in addition to being a vital part of businesses and government operations---both overt and covert. This talk will address the evolving role that the fundamental laws of quantum physics are likely to play in giving communication yet another dimension in its richness. Quantum communication will bring about not only communication in the form as we know it, but also ensure that it is unconditionally secure as it transits through any medium. Given that information is the currency of a modern society, its security is paramount for the wellbeing of an individual, a society, a nation, or the globe as a whole. The talk will discuss the short history of quantum communication and draw upon the theoretical and experimental work that the author and his colleagues have conducted over the past few years in order to chart out the likely course of future events in the emerging age of secure communication.
The primary role played by communication in our society gives importance to the problem of securely transmitting sensitive information. Quantum physics can be exploited to solve this problem in a more secure way than it is possible by using classical protocols. The application of quantum physics to communication tasks is the basis of the new quantum communication field, of which quantum cryptography represents the most successful achievement. Quantum communication, however, suffers the presence of losses much more than classical communication. The high level of losses in fiber-based systems, limiting the maximum transmission distance to a few hundred kilometers, makes it necessary to find new ways to go further. A promising solution for extending it to a worldwide scale seems to be the use of satellites. This thesis studies some aspects of quantum communication from an experimental point of view. It presents both the study in the laboratory of quantum communication protocols and the experimental characterization of the satellite-ground channel by using a simulated space source exploiting corner-cube retro-reflectors on geodesic satellites. In addition to this, it also deals with some more technical issues of the problem, such as the construction of a high brilliance polarization-entangled photon source and the improvement of the receiving station for space quantum communication at the Matera Laser Ranging Observatory.
With the recent advancements and developments in quantum technologies, the emerging field of quantum communication and networking has gained the attention of the researchers. Owing to the unique properties of quantum mechanics, viz., quantum superposition and entanglement, this new area of quantum communication has shown potential to replace modernday communication technologies. The enhanced security and high information sharing ability using principles of quantum mechanics has encouraged networking engineers and physicists to develop this technology for next generation wireless systems. However, a conceptual bridge between the fundamentals of quantum mechanics, photonics and the deployability of a quantum communication infrastructure is not well founded in the current literature. This paper aims to fill this gap by merging the theoretical concepts from quantum physics to the engineering and computing perspectives of quantum technology. This paper builds the fundamental concepts required for understanding quantum communication, reviews the key concepts and demonstrates how these concepts can be leveraged for accomplishing successful communication. The paper delves into implementation advancements for executing quantum communication protocols, explaining how hardware implementation enables the achievement of all basic quantum computing operations. Finally, the paper provides a comprehensive and critical review of the state-of-the-art advancements in the field of quantum communication and quantum internet; and points out the recent trends, challenges and open problems for the real-world realization of next generation networking systems.