Much like classical supercomputers, scaling up quantum computers requires an optical interconnect. However, signal attenuation leads to irreversible qubit loss, making quantum interconnect design guidelines and metrics different from conventional computing. Inspired by the classical Dragonfly topology, we propose a multi-group structure where the group switch routes photons emitted by computational end nodes to the group's shared pool of Bell state analyzers (which conduct the entanglement swapping that creates end-to-end entanglement) or across a low-diameter path to another group. We present a full-stack analysis of system performance, a combination of distributed and centralized protocols, and a resource scheduler that plans qubit placement and communications for large-scale, fault-tolerant systems. We implement a prototype three-node switched interconnect and create two-hop entanglement with fidelities of at least 0.6. Our design emphasizes reducing network hops and optical components to simplify system stabilization while flexibly adjusting optical path lengths. Based on evaluated loss and infidelity budgets, we find that moderate-radix switches enable systems meeting expected near-term needs, and large systems are feasible. Our design is expected to be effective for a variety of quantum computing technologies, including ion traps and superconducting qubits with appropriate wavelength transduction.

翻译：与经典超级计算机类似，量子计算机的规模化扩展需要光学互连。然而，信号衰减会导致不可逆的量子比特损耗，这使得量子互连的设计准则和评价指标不同于传统计算。受经典蜻蜓拓扑启发，我们提出一种多群组结构：群组交换机将计算终端节点发射的光子路由至该群组共享的贝尔态分析器池（通过纠缠交换实现端到端纠缠），或通过低直径路径路由至另一群组。我们提出完整的系统性能全栈分析框架，结合分布式与集中式协议，并设计资源调度器以规划大规模容错系统中的量子比特布局与通信。我们实现了三节点交换互连原型系统，成功创建保真度不低于0.6的双跳纠缠。本设计通过减少网络跳数和光学组件来简化系统稳定性控制，同时灵活调节光路长度。基于评估的损耗与失真容限分析，我们发现中等基数交换机足以满足近期预期需求，且大规模系统具备可行性。该架构预期可适用于多种量子计算技术平台，包括离子阱与经过适当波长转换的超导量子比特系统。