  Over the past few decades, significant progress has been made in quantum
information technology, from theoretical studies to experimental
demonstrations. Revolutionary quantum applications are now in the limelight,
showcasing the advantages of quantum information technology and becoming a
research hotspot in academia and industry. To enable quantum applications to
have a more profound impact and wider application, the interconnection of
multiple quantum nodes through quantum channels becomes essential. Building an
entanglement-assisted quantum network, capable of realizing quantum information
transmission between these quantum nodes, is the primary goal. However,
entanglement-assisted quantum networks are governed by the unique laws of
quantum mechanics, such as the superposition principle, the no-cloning theorem,
and quantum entanglement, setting them apart from classical networks.
Consequently, fundamental efforts are required to establish
entanglement-assisted quantum networks. While some insightful surveys have
paved the way for entanglement-assisted quantum networks, most of these studies
focus on enabling technologies and quantum applications, neglecting critical
network issues. In response, this paper presents a comprehensive survey of
entanglement-assisted quantum networks. Alongside reviewing fundamental
mechanics and enabling technologies, the paper provides a detailed overview of
the network structure, working principles, and development stages, highlighting
the differences from classical networks. Additionally, the challenges of
building wide-area entanglement-assisted quantum networks are addressed.
Furthermore, the paper emphasizes open research directions, including
architecture design, entanglement-based network issues, and standardization, to
facilitate the implementation of future entanglement-assisted quantum networks.
