The quantum internet is envisaged to connect quantum systems at a global scale to provide diverse applications unimaginable with the classical internet. However, the technological shortcomings and practical challenges of noisy intermediate-scale quantum (NISQ) devices impose several constraints on the vision of a truly global quantum internet. Recent experimental developments for quantum networks are laying the pathway from small-scale to intermediate-scale noisy quantum networks dedicated to specific operational tasks. Although these networks are not at the global scale, they are capable of providing a clear quantum advantage in their dedicated tasks. We explore the cardinal features of these NISQ networks, discuss their design constraints, and explore the possible applications they provide. We also outline some technical challenges that need to be addressed for the practical implementation of these networks and eventually lead toward a truly global, fully functional quantum internet.
The quantum internet is envisaged to connect quantum systems at a global scale to provide diverse applications unimaginable with the classical internet. However, the technological shortcomings and practical challenges of noisy intermediate-scale quantum (NISQ) devices impose several constraints on the vision of a truly global quantum internet. Recent experimental developments for quantum networks are laying the pathway from small-scale to intermediate-scale noisy quantum networks dedicated to specific operational tasks. Although these networks are not at the global scale, they are capable of providing a clear quantum advantage in their dedicated tasks. We explore the cardinal features of these NISQ networks, discuss their design constraints, and explore the possible applications they provide. We also outline some technical challenges that need to be addressed for the practical implementation of these networks and eventually lead toward a truly global, fully functional quantum internet.
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.
The current stage of quantum computing development is defined by Noisy Intermediate-Scale Quantum (NISQ) devices, which operate with a moderate number of qubits that are inherently susceptible to noise and decoherence. Despite the absence of full error correction, NISQ systems have demonstrated the ability to perform computational tasks that challenge classical simulation under certain conditions. This paper explores the concept of quantum advantage in the NISQ era by analysing prominent algorithmic approaches, benchmarking methodologies, and the practical constraints imposed by contemporary hardware. Hybrid quantum–classical algorithms, sampling-based experiments, and performance metrics are examined to assess the extent to which near-term quantum devices can outperform classical systems. The study finds that while progress toward quantum advantage is evident, significant technical and algorithmic limitations prevent its widespread realization. The paper concludes by identifying key research directions required to bridge the gap between experimental demonstrations and practical quantum computing applications.
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.
A quantum internet is an emerging quantum information technology, possibly becoming a pinnacle of wide-area distributed system allowed under the laws of physics. The current expansion of quantum technologies would lead to innumerable types of quantum systems, composed of various kinds of quantum devices connected by a dedicated quantum network. However, the (inter)connectivity offered by a quantum internet should ideally be agnostic of the technologies used by each component system. Furthermore, concurrent progresses of the quantum technologies complicate the task of defining what a quantum internet is. In this paper, we adopt a backcasting approach to elucidate what a quantum internet should be. We begin by discussing what we believe to be the requirements of an ultimate distributed quantum system, from which we explain what role a quantum internet would play in achieving this ultimate system. We then lead to more practical requirements on a quantum internet, considering the known and expected constraints in designing a quantum internet. We also organize and categorize the relationship among known quantum network technologies and services relevant to a quantum internet. We hope this document to lay a common ground for all the key stakeholders of a quantum internet, including researchers, industrial enterprises, and policy makers and regulators.
Quantum technology is now at a point where practical work can begin on creating the quantum internet. However, numerous challenges must be overcome before this vision becomes a reality. A global-scale quantum internet requires the development of the quantum repeater, a device that stores and manipulates qubits while interacting with or emitting entangled photons. This review examines different approaches to quantum repeaters and networks, covering their conceptual frameworks, architectures, and current progress in experimental implementation.
Quantum computing has emerged as a transformative paradigm capable of addressing computational challenges beyond the reach of classical systems.In the current era of Noisy Intermediate-Scale Quantum (NISQ) devices, practical quantum hardware is characterized by limited qubit counts, short coherence times, gate errors, and the absence of full error correction.Despite these constraints, significant progress has been made in developing quantum machine learning (QML) techniques tailored to operate on near-term quantum processors.This paper presents a comprehensive review of Quantum Machine Learning in the context of NISQ computing.We first outline the fundamental principles of quantum computing, including qubits, superposition, entanglement, and quantum parallelism, followed by a detailed discussion of the NISQ computing model and its hardware limitations.The review then examines hybrid quantum-classical learning frameworks, variational quantum algorithms, quantum data encoding strategies, and noise mitigation techniques that enable practical implementation on existing platforms.Emerging applications across healthcare, finance, cybersecurity, climate modeling, and materials science are also surveyed to highlight the real-world potential of QML.Furthermore, key challenges such as scalability, trainability issues, and algorithmic robustness are analyzed, along with current research efforts aimed at overcoming these barriers.The paper concludes by identifying promising future directions for advancing QML toward quantum advantage.This review aims to provide researchers and practitioners with a structured understanding of the capabilities, limitations, and opportunities of quantum machine learning in the NISQ era .