A quantum internet will provide arbitrary accessibility of distributed quantum systems, enabling secure communication, quantum computing, quantum sensing, etc. The quantum link between distant systems is established by photons flying through optical fibers and satellites. In this review, I present fundamental methods to send, manipulate and detect photonic quantum states to build a quantum internet; especially, technologies related to superconducting photon detectors.
A quantum internet will provide arbitrary accessibility of distributed quantum systems, enabling secure communication, quantum computing, quantum sensing, etc. The quantum link between distant systems is established by photons flying through optical fibers and satellites. In this review, I present fundamental methods to send, manipulate and detect photonic quantum states to build a quantum internet; especially, technologies related to superconducting photon detectors.
The Quantum Internet represents a paradigm shift in communication technology, leveraging quantum mechanical principles such as superposition, entanglement, and the no-cloning theorem to enable ultra-secure, high-fidelity, and potentially revolutionary global connectivity. Unlike the classical internet, which transmits bits through electromagnetic signals, the Quantum Internet transmits qubits, allowing the creation of unbreakable cryptographic channels, distributed quantum computation, and quantum-enhanced sensing networks. This paper presents a comprehensive review of the Quantum Internet, covering its underlying principles, layered architecture, enabling hardware technologies, and core communication protocols. We analyze current and emerging applications, from secure government and financial communications to healthcare and fundamental physics experiments. The study highlights the unique advantages of quantum networking, such as intrinsic security against eavesdropping, global-scale entanglement distribution, and integration with distributed computing infrastructures. At the same time, it addresses practical limitations, including distance constraints, quantum memory coherence times, infrastructure costs, and security risks associated with hardware vulnerabilities. Special attention is given to the feasibility of large-scale deployment in India, leveraging national programs such as NM-QTA and QuEST, as well as satellite-based quantum communication initiatives by ISRO. The paper concludes with a roadmap for the realization of a global quantum network, identifying technical, infrastructural, and policy challenges that must be addressed in the coming decades.
Entanglement distribution is a fundamental building block of quantum communication networks, enabling the secure and reliable exchange of quantum information over long distances. Unlike classical communication, quantum networks exploit the unique properties of quantum entanglement to support applications such as quantum key distribution, quantum teleportation, distributed quantum computing, and networked quantum sensing. Although significant progress has been made in recent years, the efficient generation, transmission, and preservation of entangled states remain major research challenges due to photon loss, decoherence, and limitations in current communication infrastructure.This review provides a comprehensive overview of entanglement distribution in quantum communication networks, focusing on the technologies that enable practical implementation and the latest experimental developments. It discusses key approaches for generating and distributing entangled photons through optical fibers, free-space links, and satellite-based communication, together with supporting technologies such as quantum repeaters, quantum memories, and photonic devices. The review also examines recent experimental demonstrations that have advanced long-distance quantum communication while highlighting the technical barriers that must be overcome for large-scale deployment. Finally, emerging applications and future research directions are presented, including the development of scalable quantum networks, the quantum internet, and secure global communication systems. This review aims to provide researchers and students with a clear understanding of the current state of entanglement distribution and its growing role in next-generation quantum communication technologies.
In today’s digital era, the need for communication systems that are both faster and more secure continues to grow, pushing innovation toward the development of the Quantum Internet. This paper investigates how advancements in optical switching and networking technologies are shaping this evolution by combining classical optical communication with the principles of quantum mechanics. It begins by reviewing how optical fiber systems have advanced to support high speed, low loss data transmission, forming the backbone for quantum communication infrastructure. The study explains the working principles of qubits, entanglement, and Quantum Key Distribution (QKD), which allow the transfer of data with unparalleled security through photon based signaling. Furthermore, it explores modern optical switching methods such as all optical, electro optic, and MEMS based switches, emphasizing their role in managing quantum signals efficiently while reducing energy consumption and transmission latency. The paper also highlights key network components like quantum routers, repeaters, and photonic integrated circuits that enable seamless interaction between classical and quantum networks. In addition, it reviews emerging technologies such as AI-assisted routing, low noise photon detectors, and nanophotonic materials that enhance the scalability and performance of quantum systems. The research identifies persistent challenges, including photon loss, decoherence, fabrication cost, and standardization issues, while outlining strategies to overcome them through advanced design and material innovation. Overall, this work provides a comprehensive understanding of how optical switching advancements are paving the way for a reliable, large scale, and globally connected Quantum Internet capable of transforming future communication and information security.
Quantum-communications technologies, especially involving teleportation, will play an increasingly important role in both the domestic and defense sectors because of the promise for improved security, distributed quantum computing, and quantum sensing. This paper presents a review of this emerging field, summarizing key protocols as well as some representative quantum teleportation experiments conducted both in the laboratory and in the field. Briefly, in recent years, quantum teleportation has been demonstrated in both optical-fiber networks and in long-distance free-space channels, using entanglement on photonic chips as well as between photonic and atom/ion or solid-state qubits.
The Quantum Internet - i.e. an heterogeneous network enabling quantum communications among remote quantum nodes by leveraging on quantum transmission channels in synergy with classical transmission channels - is attracting worldwide academic and industrial interest [1, 2, 3, 4, 5, 6, 7], given its potential of enabling applications with no counterpart in the classical Internet [8]. Indeed, the Quantum Internet, by transmitting qubits and by distributing entangled quantum states, comes with a whole new dazzling functionalities [9, 10].
This article envisions the concept of a ``Quantum Internet in the Sky", aiming to establish ubiquitous quantum communication links among distant nodes via free-space optical channels. Our key focus is on deploying quantum communication terminals on non-terrestrial platforms, specifically unmanned aerial vehicles and satellites, at various altitudes. By highlighting the unique characteristics of these platforms compared to terrestrial counterparts, we address inherent challenges and discuss potential solutions through meticulous system designs and analyses of typical non-terrestrial quantum communication scenarios. Finally, we illuminate the path forward by proposing essential future directions that underscore the integration of high-dimensional multipartite quantum communications with sensing, computing, and intelligence for multiple users en route to realizing a fully operational Quantum Internet.