NTT Basic Research Laboratories, NTT Corporation, 3-1, Morinosato Wakamiya, Atsugi, Kanagawa, 243-0198, Japan.
Sci Rep. 2018 Jan 16;8(1):817. doi: 10.1038/s41598-017-19078-z.
High-dimensional quantum entanglement can enrich the functionality of quantum information processing. For example, it can enhance the channel capacity for linear optic superdense coding and decrease the error rate threshold of quantum key distribution. Long-distance distribution of a high-dimensional entanglement is essential for such advanced quantum communications over a communications network. Here, we show a long-distance distribution of a four-dimensional entanglement. We employ time-bin entanglement, which is suitable for a fibre transmission, and implement scalable measurements for the high-dimensional entanglement using cascaded Mach-Zehnder interferometers. We observe that a pair of time-bin entangled photons has more than 1 bit of secure information capacity over 100 km. Our work constitutes an important step towards secure and dense quantum communications in a large Hilbert space.
高维量子纠缠可以丰富量子信息处理的功能。例如，它可以提高线性光超密集编码的信道容量，并降低量子密钥分发的错误率阈值。在通信网络中进行这种先进的量子通信，需要远距离分发高维纠缠。在这里，我们展示了一种四维度纠缠的远距离分发。我们采用适用于光纤传输的时间-bin 纠缠，并使用级联马赫-曾德尔干涉仪对高维纠缠进行可扩展的测量。我们观察到一对时间-bin 纠缠光子在 100 公里以上的传输距离中具有超过 1 比特的安全信息容量。我们的工作是朝着在大 Hilbert 空间中进行安全和密集的量子通信迈出的重要一步。
