As quantum theory allows for information processing and computing tasks that
otherwise are not possible with classical systems, there is a need and use of
quantum Internet beyond existing network systems. At the same time, the
realization of a desirably functional quantum Internet is hindered by
fundamental and practical challenges such as high loss during transmission of
quantum systems, decoherence due to interaction with the environment, fragility
of quantum states, etc. We study the implications of these constraints by
analyzing the limitations on the scaling and robustness of quantum Internet.
Considering quantum networks, we present practical bottlenecks for secure
communication, delegated computing, and resource distribution among end nodes.
Motivated by the power of abstraction in graph theory (in association with
quantum information theory), we consider graph-theoretic quantifiers to assess
network robustness and provide critical values of communication lines for
viable communication over quantum Internet.
In particular, we begin by discussing limitations on usefulness of isotropic
states as device-independent quantum key repeaters which otherwise could be
useful for device-independent quantum key distribution. We consider some
quantum networks of practical interest, ranging from satellite-based networks
connecting far-off spatial locations to currently available quantum processor
architectures within computers, and analyze their robustness to perform quantum
information processing tasks. Some of these tasks form primitives for delegated
quantum computing, e.g., entanglement distribution and quantum teleportation.
For some examples of quantum networks, we present algorithms to perform
different quantum network tasks of interest such as constructing the network
structure, finding the shortest path between a pair of end nodes, and
optimizing the flow of resources at a node.Comment: Happy about the successful soft landing of Chandrayaan-3 on the moon
by ISRO. 35 pages, 32 figures. Preliminary versio