  Quantum networks will play a key role in distributed quantum information
processing. As the network size increases, network-level errors like random
breakdown and intentional attack are inevitable; therefore, it is important to
understand the robustness of large-scale quantum networks, similar to what has
been done for the classical counterpart---the Internet. For exponential
networks such as Waxman networks, errors simply re-parameterize the network and
lead to a linear decrease of the quantum capacity with the probability of
error. The same linear decay happens for scale-free quantum networks under
random breakdowns, despite the previously discovered robustness in terms of the
connectivity. In presence of attack, however, the capacity of scale-free
quantum networks shows a sharp exponential decay with the increasing attack
fraction. Our results apply to quantum internet based on fibers for all kinds
of quantum communications and provide implications for the future construction
of quantum networks with regard to its robustness.
