Quantum networks that allow generating entangled states between distant qubits have enormous scientific and applied potential. They can be used for secure quantum cryptography and the teleportation of quantum states between cities and countries, in high-resolution astronomy, and in distributed quantum computing. The scattering of photons in an optical fiber and the difficulties in creating full-fledged quantum nodes impede the construction of large quantum networks. We review current approaches to the creation of such networks, with the emphasis on quantum repeaters intended for ‘compensating’ losses in optical fibers. We also discuss methods for increasing the range of quantum cryptography systems without using quantum repeaters.

允许在遥远的量子位之间产生纠缠态的量子网络具有巨大的科学和应用潜力。它们可用于安全的量子密码学和城市和国家之间的量子态隐形传输、高分辨率天文学和分布式量子计算。光纤中光子的散射以及创建成熟量子节点的困难阻碍了大型量子网络的构建。我们回顾了当前创建此类网络的方法，重点是旨在“补偿”光纤损耗的量子中继器。我们还讨论了在不使用量子中继器的情况下增加量子密码系统范围的方法。