F.Xu

Kejin Wei, Nora Tischler, Si-Ran Zhao, Yu-Huai Li, Juan Miguel Arrazola, Yang Liu, Weijun Zhang, Hao Li, Lixing You, Zhen Wang, Yu-Ao Chen, Barry Sanders, Qiang Zhang, Geoff Pryde, Feihu Xu and Jian-Wei Pan
We experimentally demonstrate exponentially superior quantum communication complexity by realizing a superposition of communication directions for a two-party distributed computation. Our photonic demonstration employs $d$-dimensional quantum systems, qudits, up to $d=2^{13}$ dimensions and demonstrates a communication complexity advantage, requiring less than $(0.696 \pm 0.006)$ times the communication of any causally ordered protocol. These results elucidate the crucial role of the coherence of communication direction in achieving the exponential separation for the one-way processing task, and open a new path for experimentally exploring the fundamentals and applications of advanced features of indefinite causal structures.

Zheng-Da Li, Rui Zhang, Xu-Fei Yin, Li-Zheng Liu, Yi Hu, Yu-Qiang Fang, Yue-Yang Fei, Xiao Jiang, Jun Zhang, Feihu Xu, Yu-Ao Chen and Jian-Wei Pan
Quantum repeaters – important component of the quantum internet – enable the entanglement to be distributed over long distances. A standard quantum repeater relies on a necessary demanding requirement of quantum memory. Despite significant progress, the limited performance of quantum memory makes practical quantum repeaters still a challenge. Remarkably, a proposed all-photonic quantum repeater avoids the need for quantum memory. Here we perform an experimental demonstration of an all-photonic quantum repeater by manipulating a 12-photon interferometer and observe an 89% enhancement of entanglement-generation rate over the parallel entanglement swapping. These results open a new way towards realizing practical quantum repeaters.