At the fundamental level, quantum communication is ultimately limited by noise. For instance, quantum signals cannot be amplified without the introduction of noise in the amplified states. Furthermore, photon loss reduces the signal-to-noise ratio, accentuating the effect of noise. Thus, most of the efforts in quantum communications have been directed towards overcoming noise to achieve longer communication distances, larger secret key rates, or to operate in noisier environmental conditions. Here, we propose and experimentally demonstrate a platform for quantum communication based on ultrafast optical techniques. In particular, our scheme enables the experimental realization of high-rates and quantum signal filtering approaching a single spectro-temporal mode, resulting in a dramatic reduction in channel noise. By experimentally realizing a 1-ps optically induced temporal gate, we show that ultrafast time filtering can result in an improvement in noise tolerance by a factor of up to 1200 compared to a 2-ns electronic filter enabling daytime quantum key distribution or quantum communication in bright fibers.
Achieving fault tolerance on capped color codes with few ancillas
在保持低开销的同时实现容错是量子线路的实际实现中的主要挑战之一。一个主要的技术，可以克服这个问题是标志技术，其中产生的几个故障的高权重的错误，可以检测到的几个ancillas和区分使用随后的症状测量。该技术可以使用以下事实进一步改进：对于某些代码族，如果它们具有相同的伴随式和权重奇偶校验，则任何权重的错误在逻辑上是等效的，如先前在[Phys.Rev.A104，042410（2021）]中所示。在这项工作中，我们开发了一个可区分的故障集的概念，它捕获了标志和权重奇偶校验的概念，并将权重奇偶校验在纠错中的使用从[Phys. Rev. A 104，042410（2021）]扩展到capped和递归capped色码的家族。我们还开发了容错协议的纠错，测量，状态准备，和逻辑T门的实现，通过代码切换，这是足够的执行容错Clifford计算的上限色码，并执行容错通用量子计算的递归上限色码。我们的协议的上限或递归上限的颜色代码的任何距离只需要2 ancillas，假设可以重用的ancillas。可区分故障集的概念也导致了Aliferis，Gottesman和Preskill提出的容错小工具的定义的推广。
Geometry-optimized hyperbolic codes for modular fault-tolerant quantum architectures
University of Saskatchewan（萨斯喀彻温大学）；Centre for Quantum Topology and Its Applications (quanTA)（量子拓扑及其应用中心）；Department of Mathematics and Statistics（数学与统计系）
