Quantum communication infrastructures are being built worldwide to establish a quantum secure communication shield across geographical areas to protect economies, societies, and individuals from cyberthreats. It is a first step toward interconnecting nodes with classical/quantum communication, computation, and storage capabilities. However, insufficient emphasis has been placed on the fact that such infrastructure will not operate like classical networks, even though they must operate in conjunction with classical networks. In particular, classical and quantum resources can be generated and/or consumed to realize quantum protocols (e.g., a teleportation protocol consumes two classical information bits and one entanglement bit (ebit) to deliver one quantum bit (qubit)). This fundamental paradigm shift with respect to current (Shannon) classical communication brings fundamental network design challenges. In this work, we focus on the increasingly relevant space-terrestrial integrated networks, and investigate such challenges. First, we introduce the interplay between classical and quantum network resources according to the underlying theoretical limits band, and justify why the problem is significant and needs to be addressed urgently. Second, we present two illustrative numerical analyses: trade-offs between classical-quantum and classical-entanglement capacities, both over space channels. We identify (both technical and policy/ethical) research challenges ahead for the staged development of integrated quantum-classical networks as the required quantum technology becomes available. Finally, we identify the synergies with 6G usage scenarios endorsed by ITU-R.
Quantum communication infrastructures are being built worldwide to establish a quantum secure communication shield across geographical areas to protect economies, societies, and individuals from cyberthreats. It is a first step toward interconnecting nodes with classical/quantum communication, computation, and storage capabilities. However, insufficient emphasis has been placed on the fact that such infrastructure will not operate like classical networks, even though they must operate in conjunction with classical networks. In particular, classical and quantum resources can be generated and/or consumed to realize quantum protocols (e.g., a teleportation protocol consumes two classical information bits and one entanglement bit (ebit) to deliver one quantum bit (qubit)). This fundamental paradigm shift with respect to current (Shannon) classical communication brings fundamental network design challenges. In this work, we focus on the increasingly relevant space-terrestrial integrated networks, and investigate such challenges. First, we introduce the interplay between classical and quantum network resources according to the underlying theoretical limits band, and justify why the problem is significant and needs to be addressed urgently. Second, we present two illustrative numerical analyses: trade-offs between classical-quantum and classical-entanglement capacities, both over space channels. We identify (both technical and policy/ethical) research challenges ahead for the staged development of integrated quantum-classical networks as the required quantum technology becomes available. Finally, we identify the synergies with 6G usage scenarios endorsed by ITU-R.
Abstract Over the past four decades, quantum communication has evolved as a dynamic interdisciplinary field, advancing theoretical concepts and practical implementations. This article provides a concise overview focusing on recent progress in different aspects of secure quantum communication and quantum computation protocols, which can be applied to several real-world applications in quantum networks. These protocols guarantee unconditional security while enhancing communication rates and computation capabilities by harnessing quantum advantages. We also explore the role of non-terrestrial networks in quantum applications, with a focus on quantum technologies such as quantum key distribution and beyond, suitable for satellite-based applications. These technologies can contribute to future extensions of the quantum internet across intercontinental territories, connecting complex quantum network applications. Further, we delve into discussing the integration of quantum communication into 6G technology. The key innovation of this article lies in integrating quantum communication into 6G networks through a novel system-level simulation framework. 6G-enabled quantum networks are expected to meet the high demands on ubiquitous coverage, data rate, latency, and energy consumption. To address these issues, we design and evaluate four traffic demand scenarios using numerical simulation, illustrating how superdense coding doubles the data transmission rate and fulfills the high traffic demands on data rate, while under low traffic demand, entanglement resources can be reserved for future applications. Specifically, our investigation demonstrates how resource utilization adapts to different traffic demands, with adjustments based on available resources and practical constraints, evaluated over an ideal noise-free communication channel. The proof-of-work simulation is implemented using Python and is based on the system model we designed for varying traffic demands to pave the way for efficient quantum networks and gain deeper insights into their feasibility with available resources.
The advanced notebooks, mobile phones, and internet applications in today’s world that we use are all entrenched in classical communication bits of zeros and ones. Classical internet has laid its foundation originating from the amalgamation of mathematics and Claude Shannon’s theory of information. However, today’s internet technology is a playground for eavesdroppers. This poses a serious challenge to various applications that rely on classical internet technology, and it has motivated the researchers to switch to new technologies that are fundamentally more secure. By exploring the quantum effects, researchers paved the way into quantum networks that provide security, privacy, and range of capabilities such as quantum computation, communication, and metrology. The realization of Quantum Internet (QI) requires quantum communication between various remote nodes through quantum channels guarded by quantum cryptographic protocols. Such networks rely upon quantum bits (qubits) that can simultaneously take the value of zeros and ones. Due to the extraordinary properties of qubits such as superposition, entanglement, and teleportation, it gives an edge to quantum networks over traditional networks in many ways. At the same time, transmitting qubits over long distances is a formidable task and extensive research is going on satellite-based quantum communication, which will deliver breakthroughs for physically realizing QI in near future. In this paper, QI functionalities, technologies, applications and open challenges have been extensively surveyed to help readers gain a basic understanding of the infrastructure required for the development of the global QI.
The Quantum Internet, a network interconnecting remote quantum devices through quantum links in synergy with classical ones, is envisioned as the final stage of the quantum revolution, opening fundamentally new communications and computing capabilities. But the Quantum Internet is governed by the laws of quantum mechanics. Phenomena with no counterpart in classical networks, such as no-cloning, quantum measurement, entanglement and quantum teleportation, impose new challenging constraints for network design. Specifically, classical network functionalities are based on the assumption that classical information can be safely read and copied. However, this assumption does not hold in the Quantum Internet. As a consequence, its design requires a major network-paradigm shift to harness the quantum mechanics specificities. The goal of this work is to shed light on the challenges and open problems of Quantum Internet design. We first introduce some basic knowledge of quantum mechanics, needed to understand the differences between a classical and a quantum network. Then, we introduce quantum teleportation as the key strategy for transmitting quantum information without physically transferring the particle that stores the quantum information or violating the principles of quantum mechanics. Finally, the key research challenges to design quantum communication networks are discussed.
In the coming years, space missions will increasingly require communication systems capable of ensuring high-performance, safe, and reliable data transmission between ground stations and spacecraft. Since classical communication systems will be inadequate and have enormous limitations, this article intends to analyze the potential of quantum networking in addressing future challenges of space communications. We introduce well-known phenomena of quantum mechanics, such as non-cloning, entanglement, quantum measurement, and quantum teleportation, which open up a completely new scenario in the design of the communication network. Finally, we propose a network architecture for space exploration, aiming to take a look at the potential of quantum technology to establish communication between Earth and spacecraft by integrating terrestrial and non-terrestrial quantum networks.
Quantum communication represents a revolutionary advancement over classical information theory, which leverages unique quantum mechanics properties like entanglement to achieve unprecedented capabilities in secure and efficient information transmission. Unlike bits in classical communication, quantum communication utilizes qubits in superposition states, allowing for novel information storage and processing. Entanglement, a key quantum phenomenon, enables advanced protocols with enhanced security and processing power. This paper provides a comprehensive overview of quantum communication, emphasizing the role of entanglement in theoretical foundations, practical protocols, experimental progress, and security implications. It contrasts quantum communications potential applications with classical networks, identifying areas where entanglement offers significant advantages. The paper explores the fundamentals of quantum mechanics in communication, the physical realization of quantum information, and the formation of secure quantum networks through entanglement-based strategies like Quantum Key Distribution (QKD) and teleportation. It addresses the challenges of long-distance quantum communication, the role of quantum repeaters in scaling networks, and the conceptualization of interconnected quantum networks. Additionally, it discusses strides towards the Quantum Internet, Quantum Error-Correcting codes, and quantum cryptographys role in ensuring secure communication. By highlighting the role of entanglement, this paper aims to inspire further research and innovation in secure and efficient information exchange within quantum networks.
As the world prepares for the advent of 6G networks, quantum technologies are becoming critical enablers of the next generation of communication systems. This survey paper investigates the convergence of quantum technologies and 6G networks, focusing on their applications, opportunities and challenges. We begin with an examination of the motivations for integrating quantum technologies into 6G, investigating the potential to overcome the limits of classical computing and cryptography. We then highlight key research gaps, particularly in quantum communication, quantum computing integration and security enhancement. A comprehensive overview of quantum technologies relevant to 6G, including quantum communication devices, quantum computing paradigms, and hybrid quantum-classical approaches is provided. A particular focus is on the role of quantum technologies in enhancing 6G Radio Access Networks (RAN), 6G core and edge network optimization, and 6G security. The survey paper also explores the application of quantum cryptography with a focus on Quantum Key Distribution (QKD), Quantum Secure Direct Communication (QSDC) and quantum-resistant cryptographic algorithms and assesses their implementation challenges and potential impact on 6G networks. We also discuss the significant challenges associated with integrating quantum technologies into existing communications infrastructures, including issues of technological maturity, standardization, and economic considerations. Finally, we summarize the lessons learned from current research and outline future research directions to guide the ongoing development of quantum-enabled 6G networks.