光纤Sagnac干涉仪中单光子干涉及路由控制

介绍一种光纤中稳定的单光子干涉以及单光子路由控制方式. 使用Sagnac单光子环形干涉仪，通过分时相位调制，改变其顺时针和逆时针两路光子间的相位差. 在Sagnac单光子环形干涉仪中，顺时针和逆时针两路光子走过的是同一段光纤，简便有效地补偿了光纤长度随时间缓变带来的相位涨落，而且两路光子经历了相同的偏振模色散，较好地抑制了偏振态波动对单光子干涉的影响. 在长达5km的1550nm单模光纤中，获得大于98%的单光子干涉和大于90%单光子路由控制；在长度为27和50km光纤环路中，分别获得大于94%和84%单关键词：单光子路由单光子干涉Sagnac单光子环形干涉仪量子保密通信

Single-photon interference and router-control in an optic fiber Sagnac interferometer

A novel scheme to realize stable single-photon interference and router-control is demonstrated in this paper. Phase difference between clockwise and counter-clockwise single-photons is controlled by time-division phase modulation in an optic fiber Sagnac loop. Due to the annular geometric configuration of the Sagnac loop, clockwise and counter-clockwise single-photons travel the same optical path and have the same slowly-varying phase drifts, which are automatically compensated. Furthermore, clockwise and counter-clockwise single-photons encounter the same polarization mode dispersion, which is also automatically compensated at the exit port of the Sagnac interferometer. Long-distance single-mode optic fiber at 1550 nm is used in our experimental realization. Fringe visibility of single-photon interference higher than 98% and fidelity of single-photon router-control higher than 90% have been obtained in a Sagnac fiber loop of 5 km. We also realized a stable single-photon interference in Sagnac fiber loops as long as 27 and 52 km. The corresponding fringe visibilities were higher than 94% and 84%, respectively.