The Quantum Internet, by enabling quantum communications among remote quantum nodes, is a network capable of supporting functionalities with no direct counterpart in the classical world. Indeed, with the network and communications functionalities provided by the Quantum Internet, remote quantum devices can communicate and cooperate for solving challenging computational tasks by adopting a distributed computing approach. The aim of this study is to provide the reader with an overview about the main challenges and open problems arising in the design of a distributed quantum computing ecosystem. For this, the authors provide a survey, following a bottom‐up approach, from a communications engineering perspective. They start by introducing the Quantum Internet as the fundamental underlying infrastructure of the distributed quantum computing ecosystem. Then they go further, by elaborating on a high‐level system abstraction of the distributed quantum computing ecosystem. They describe such an abstraction through a set of logical layers. Thereby, they clarify dependencies among the aforementioned layers and, at the same time, a road‐map emerges.

Quantum Teleportation is the key communication functionality of the Quantum Internet, allowing the “transmission” of qubits without the physical transfer of the particle storing the qubit. Quantum teleportation is facilitated by the action of quantum entanglement, a somewhat counter-intuitive physical phenomenon with no direct counterpart in the classical word. As a consequence, the very concept of the classical communication system model has to be redesigned to account for the peculiarities of quantum teleportation. This re-design is a crucial prerequisite for constructing any effective quantum communication protocol. The aim of this manuscript is to shed light on this key concept, with the objective of allowing the reader: i) to appreciate the fundamental differences between the transmission of classical information versus the teleportation of quantum information; ii) to understand the communications functionalities underlying quantum teleportation, and to grasp the challenges in the design and practical employment of these functionalities; iii) to acknowledge that quantum information is subject to the deleterious effects of a noise process termed as quantum decoherence. This imperfection has no direct counterpart in the classical world; iv) to recognize how to contribute to the design and employment of the Quantum Internet.

In distributed quantum computing architectures, with the network and communications functionalities provided by the Quantum Internet, remote quantum processing units can communicate and cooperate for executing computational tasks that single, noisy, intermediate-scale quantum devices cannot handle by themselves. To this aim, distributed quantum computing requires a new generation of quantum compilers, for mapping any quantum algorithm to any distributed quantum computing architecture. With this perspective, in this article, we first discuss the main challenges arising with compiler design for distributed quantum computing. Then, we analytically derive an upper bound of the overhead induced by quantum compilation for distributed quantum computing. The derived bound accounts for the overhead induced by the underlying computing architecture as well as the additional overhead induced by the suboptimal quantum compiler—expressly designed in this article to achieve three key features, namely, general-purpose , efficient , and effective . Finally, we validate the analytical results, and we confirm the validity of the compiler design through an extensive performance analysis.

The deployment of 5G networks will necessarily involve the installation of new base station (BS) equipment to support the requirements of next-generation mobile services. In a scenario where there exist already many sources of electromagnetic fields (EMFs), including overlapping 2G/3G/4G technologies of competing network operators, there is a growing concern that the planning of a 5G network will be severely constrained by the limits on maximum EMF levels established in a wide set of regulations. The goal of this paper is to shed light on EMF-aware 5G network planning and, in particular, on the problem of site selection for 5G BS equipment that abides by downlink EMF limits. To this end, we present the current state of the art in EMF-aware mobile networking and overview the current exposure limits and how the EMF constraints may impact 5G planning. We then substantiate our analysis by reporting on two realistic case studies, which demonstrate the saturation of EMF levels already occurring under current 2G/3G/4G networks, as well as the negative impact of strict regulations on network planning and user quality of service. Finally, we discuss the expected impact of 5G technologies in terms of EMFs and draw the guidelines for an EMF-aware planning of 5G. Our analysis suggests that the EMF-aware 5G planning risks to be a real challenge for network operators, which stimulates further actions at governmental, societal, technological, and research levels.

Practical distributed quantum computing requires the development of efficient compilers, able to make quantum circuits compatible with some given hardware constraints. This problem is known to be tough, even for local computing. Here, we address it on distributed architectures. As generally assumed in this scenario, telegates represent the fundamental remote (inter-processor) operations. Each telegate consists of several tasks: (i) entanglement generation and distribution, (ii) local operations, and (iii) classical communications. Entanglement generations and distribution is an expensive resource, as it is time-consuming. To mitigate its impact, we model an optimization problem that combines running-time minimization with the usage of distributed entangled states. Specifically, we formulated the distributed compilation problem as a dynamic network flow. To enhance the solution space, we extend the formulation, by introducing a predicate that manipulates the circuit given in input and parallelizes telegate tasks. To evaluate our framework, we split the problem into three sub-problems, and solve it by means of an approximation routine. Experiments demonstrate that the run-time is resistant to the problem size scaling. Moreover, we apply the proposed algorithm to compile circuits under different topologies, showing that topologies with a higher ratio between edges and nodes give rise to shallower circuits.