Quantum communication capacity transition of complex quantum networks
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Quantum network is the key to enable distributed quantum information processing. As the single-link communication rate decays exponentially with the distance, to enable reliable end-to-end quantum communication, the number of nodes need to grow with the network scale. For highly connected networks, we identify a threshold transition in the capacity as the density of network nodes increases—below a critical density, the rate is almost zero, while above the threshold the rate increases linearly with the density. Surprisingly, above the threshold the typical communication capacity between two nodes is independent of the distance between them, due to multi-path routing enabled by the quantum network. In contrast, for less connected networks such as scale-free networks, the end-to-end capacity saturates to constants as the number of nodes increase, and always decays with the distance; Our results are based on capacity evaluations, therefore is universal for general architectures and protocols of quantum networks.
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