  The research of architecture has tremendous significance in realizing quantum
Internet. Although there is not yet a standard quantum Internet architecture,
the distributed architecture is one of the possible solutions, which utilizes
quantum repeaters or dedicated entanglement sources in a flat structure for
entanglement preparation & distribution. In this paper, we analyze the
distributed architecture in detail and demonstrate that it has three
limitations: 1) possible high maintenance overhead, 2) possible low-performance
entanglement distribution, and 3) unable to support optimal entanglement
routing. We design a hierarchical quantum Internet architecture and a
communication model to solve the problems above. We also present a W-state
Based Centralized Entanglement Preparation & Distribution (W-state Based CEPD)
scheme and a Centralized Entanglement Routing (CER) algorithm within our
hierarchical architecture and perform an experimental comparison with other
entanglement preparation & distribution schemes and entanglement routing
algorithms within the distributed architecture. The evaluation results show
that the entanglement distribution efficiency of hierarchical architecture is
11.5% higher than that of distributed architecture on average (minimum 3.3%,
maximum 37.3%), and the entanglement routing performance of hierarchical
architecture is much better than that of a distributed architecture according
to the fidelity and throughput.
