The reliable provision of entangled qubits is an essential precondition in a variety of schemes for distributed quantum computing. This is challenged by multiple nuisances, such as errors during the transmission over quantum links, but also due to degradation of the entanglement over time due to decoherence. The latter can be seen as a constraint on the latency of the quantum protocol, which brings the problem of quantum protocol design into the context of latency-reliability constraints. We address the problem through hybrid schemes that combine: (1) indirect transmission based on teleportation and distillation; (2) direct transmission, based on quantum error correction (QEC). The intuition is that, at present, the quantum hardware offers low fidelity, which demands distillation; on the other hand, low latency can be obtained by QEC techniques. It is shown that, in the proposed framework, the distillation protocol gives rise to asymmetries that can be exploited by asymmetric quantum error correcting code (QECC), which sets the basis for unique hybrid distillation and coding design. Our results show that ad-hoc asymmetric codes give, compared to conventional QEC, a performance boost and codeword size reduction both in a single link and in a quantum network scenario.

翻译：可靠地提供纠缠量子比特是分布式量子计算多种方案中的基本前提。这一目标受到多重干扰因素的挑战，例如量子链路传输过程中的误差，以及因退相干导致的纠缠态随时间退化。后者可视为量子协议延迟约束，从而将量子协议设计问题置于延迟-可靠性约束的框架中。我们通过混合方案解决该问题，该方案结合了：（1）基于隐形传态与蒸馏的间接传输；（2）基于量子纠错（QEC）的直接传输。其核心思想是：当前量子硬件保真度较低，需要蒸馏操作；另一方面，通过QEC技术可获得低延迟性能。研究表明，在所提框架中，蒸馏协议产生的不对称性可被非对称量子纠错码（QECC）所利用，这为独特的混合蒸馏与编码设计奠定了基础。我们的结果表明，与常规QEC相比，定制化的非对称码在单链路和量子网络场景中均能实现性能提升与码字尺寸缩减。