The primary task of a quantum repeater network is to deliver entanglement among end nodes. Most of existing entanglement distribution protocols do not consider purification, which is thus delegated to an upper layer. This is a major drawback since, once an end-to-end entangled connection (or a portion thereof) is established it cannot be purified if its fidelity (F) does not fall within an interval bounded by Fmin (greater than 0.5) and Fmax (less than 1). In this paper, we propose the Ranked Entanglement Distribution Protocol (REDiP), a connection-oriented protocol that overcomes the above drawback. This result was achieved by including in our protocol two mechanisms for carrying out jointly purification and entanglement swapping. We use simulations to investigate the impact of these mechanisms on the performance of a repeater network, in terms of throughput and fidelity. Moreover, we show how REDiP can easily be configured to implement custom entanglement swapping and purification strategies, including (but not restricted to) those adopted in two recent works.

翻译：量子中继网络的首要任务是在终端节点之间分发纠缠。现有的大多数纠缠分发协议未考虑纯化，因此将纯化任务委托给上层。这是一个重大缺陷，因为一旦建立端到端纠缠连接（或其一部分），若其保真度F不在Fmin（大于0.5）和Fmax（小于1）界定的区间内，则无法进行纯化。本文提出排序纠缠分发协议（REDiP），这是一种面向连接的协议，克服了上述缺陷。该成果是通过在协议中引入两种可联合执行纯化与纠缠交换的机制实现的。我们利用仿真研究这些机制对中继网络性能的影响（以吞吐量和保真度为指标）。此外，我们展示了REDiP可轻松配置以实现自定义的纠缠交换与纯化策略，包括（但不限于）近期两项工作中所采用的策略。