The quantum Internet relies on the ability to distribute entangled quantum bits (ebits) between quantum memories at the end nodes, to perform applications like blind or distributed quantum computing that are impossible if end nodes are connected via a classical, i.e., non-quantum network. This need creates new challenges due to the fragile nature of entanglement, which decoheres over short timescales and cannot be amplified, buffered, or retransmitted. Two broad categories of approaches have been proposed in the scientific literature to realize such an entanglement distribution in a given path: one relying on a synchronous time-slotted model, and another one where intermediate nodes interact asynchronously. However, both of them implicitly assume a serial operation, where one ebit is established and made available to the application on end nodes before creating a new one. This is inefficient in long-range networks, with high transmission latencies, if the intermediate nodes have multiple memory qubits that could be used in parallel. To overcome this limitation, in this paper, we study the implications of multiplexing concurrent ebit requests on the same quantum, for both synchronous and asynchronous operation. Furthermore, for the latter, we define a novel distribution protocol, called HOPPER, where the intermediate nodes make autonomous and hop-by-hop decisions on the use of their local resources when establishing an ebit. With numerical simulations, we show that HOPPER is effective in handling multiple ebit requests in parallel, and it exhibits significantly better performance than a synchronous alternative in different scenarios.

翻译：论文摘要：量子互联网依赖于在端节点量子存储器之间分发纠缠量子比特（ebits）的能力，以执行盲量子计算或分布式量子计算等应用，这些应用在端节点通过经典（即非量子）网络连接时是无法实现的。由于纠缠态的脆弱性——其在短时间尺度内退相干且无法被放大、缓冲或重传——这一需求带来了新的挑战。现有文献中提出了两类实现特定路径上纠缠分发的方法：一类基于同步时隙模型，另一类中中间节点异步交互。然而，这两种方法均隐含串行操作假设，即在完成一个ebit的建立并使其可供端节点应用使用后，才进行下一个ebit的创建。对于具备多个可用于并行操作的存储量子比特的中间节点而言，这种串行模式在具有高传输延迟的长距离网络中效率低下。为克服这一局限，本文研究了在同一量子信道上对并发ebit请求进行复用的影响，涵盖同步与异步两种操作模式。进一步，针对异步模式，我们定义了一种名为HOPPER的新型分发协议，其中中间节点在建立ebit时，基于本地资源自主做出逐跳决策。通过数值仿真，我们证明HOPPER能有效并行处理多个ebit请求，并在多种场景下展现出显著优于同步方案的性能。