End-to-end capacities of imperfect-repeater quantum networks

Abstract

The optimal performance of a communication network is limited not only by the quality of point-to-point channels but by the efficacy of its constituent technologies. Understanding the limits of quantum networks requires an understanding of both the ultimate capacities of quantum channels and the efficiency of imperfect quantum repeaters. In this work, using a recently developed node-splitting technique that introduces internal losses and noise into repeater devices, we present achievable end-to-end rates for noisy-repeater quantum networks. These are obtained by extending the coherent and reverse coherent information (single channel capacity lower bounds) into end-to-end capacity lower bounds, both in the context of single-path and multi-path routing. These achievable rates are completely general and apply to networks composed of arbitrary channels arranged in general topologies. Through this general formalism, we show how tight upper-bounds can also be derived by supplementing appropriate single-edge capacity bounds. As a result, we develop tools that provide tight performance bounds for quantum networks constituent of channels whose capacities are not exactly known and reveal critical network properties which are necessary for high-rate quantum communications. This permits the investigation of pertinent classes of quantum networks with realistic technologies; qubit amplitude damping networks and bosonic thermal-loss networks.

Optimal quantum key distribution networks: capacitance versus security

“…The optimization of quantum communication networks involves therefore the closing of security loopholes and the mitigation of the effect of losses through the development of quantum communication protocols, such as for example the measurement device independent QKD [15][16][17] and the twin-field QKD 18 protocols. But it is also pursued by optimizing the allocation of quantum resources for quantum sensing 19 and for distributed quantum computing 20 or by engineering optimal routing strategies [21][22][23][24][25] , taking into account the peculiar features of the network elements and the network architecture.…”