  Quantum communications is a promising technology that will play a fundamental
role in the design of future networks. In fact, significant efforts are being
dedicated by both the quantum physics and the classical communications
communities on developing new architectures, solutions, and practical
implementations of quantum communication networks (QCNs). Although these
efforts led to various advances in today's technologies, there still exists a
non-trivial gap between the research efforts of the two communities on
designing and optimizing the performance of QCNs. For instance, most prior
works by the classical communications community ignore important quantum
physics-based constraints when designing QCNs. For example, many existing works
on entanglement distribution do not account for the decoherence of qubits
inside quantum memories and, thus, their designs become impractical since they
assume an infinite lifetime of quantum states. In this paper, we bring forth a
novel analysis of the performance of QCNs in a physics-informed manner, by
relying on the quantum physics principles that underly the different components
of QCNs. The need of the physics-informed approach is then assessed and its
fundamental role in designing practical QCNs is analyzed across various open
research areas. Moreover, we identify novel physics-informed performance
metrics and controls that enable QCNs to leverage the state-of-the-art
advancements in quantum technologies to enhance their performance. Finally, we
analyze multiple pressing challenges and open research directions in QCNs that
must be treated using a physics-informed approach to lead practically viable
results. Ultimately, this work attempts to bridge the gap between the classical
communications and the quantum physics communities in the area of QCNs to
foster the development of the future communication networks towards the quantum
Internet.
