基于单原子的异步光子互连用于可扩展模块化量子计算

中文摘要 AI 辅助

将量子计算扩展到单个量子处理单元的能力之外，需要在模块化处理器之间建立量子互连。光学光子是在这些处理器之间分发纠缠的天然载体。大多数抗损耗协议使用基于线性光学II型融合门的光子贝尔态测量。由此产生的纠缠率随每个处理器通常较低的光子传递概率呈二次方缩放。在此，我们分析了一种基于存储器的量子互连，该互连利用高精细度腔中捕获的单原子，通过近确定性的、鲁棒的光子-原子受控Z门实现。检测并测量来自一个处理器的光子，宣告该处理器与原子之间的纠缠建立。在重复该过程与第二个处理器时，此纠缠得以保持，直到第二个光子被检测并测量。读出原子量子比特最终完成处理器之间的纠缠。由于纠缠由原子介导，来自两个处理器的光子无需不可区分，从而消除了一个主要的保真度损失来源。此外，通过消除同时光子到达的要求，该协议允许纠缠率在广泛参数范围内随光子到达概率线性而非二次方缩放。我们在现实参数下推导纠缠率，考虑了原子与第一个处理器纠缠的衰减以及未宣告光子相互作用引起的退相干。门操作和读出操作的纳秒级时间尺度导致纠缠率比线性光学高出数个数量级，消除了模块化量子计算中的一个关键瓶颈。

英文摘要

Scaling quantum computation beyond the capacity of a single quantum processing unit requires quantum interconnects between modular processors. Optical photons are natural carriers for distributing entanglement between these processors. Most loss-resilient protocols use photonic Bell-state measurements based on the linear-optics type-II fusion gate. The resulting entanglement rate scales quadratically with each processor's typically low photon-delivery probability. Here we analyze a memory-assisted quantum interconnect using a near-deterministic, robust photon--atom controlled-$Z$ gate via a single atom trapped in a high-finesse cavity. Detecting and measuring a photon from one processor heralds entanglement between that processor and the atom. This entanglement is preserved while the process repeats with the second processor until the second photon is detected and measured. Reading out the atomic qubit finalizes the entanglement between the processors. As the entanglement is mediated by the atom, the photons from both processors do not need to be indistinguishable, removing a major source of infidelity. Furthermore, by removing the simultaneous photon-arrival requirement, the protocol allows the entanglement rate to scale linearly rather than quadratically with photon-arrival probability over a wide parameter range. We derive entanglement rates under realistic parameters, accounting for decay of the atom's entanglement with the first processor and for decoherence caused by unheralded photon interactions. The nanosecond-scale of the gate and read-out operations leads to orders-of-magnitude entanglement-rate gain over linear optics, removing a key bottleneck in modular quantum computing.

发表机构

• Quantum Source Labs Ltd（量子源实验室有限公司）
• Institute of Science and Technology Austria (ISTA)（奥地利科学技术研究所）
• Weizmann Institute of Science（魏茨曼科学研究所）

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