Using an all-fiber source of pulsed twin beams, with the record intensity difference squeezing of $6.1\pm 0.15\mathrm{dB}$ for fiber optical parametric amplifiers, we experimentally distribute the pulsed continuous variable (CV) quantum state over a long distance. After separating the signal and idler twin beams by 26 km single-mode fibers, the measured intensity difference noise is still below the shot noise limit by 2 dB. The result shows that the distribution process is only affected by the vacuum noise originated from the fiber transmission loss. The extra noise contributed by the acoustic wave Brillouin scattering and Raman scattering in 26 km transmission fibers has not been observed. The investigation is beneficial for studying long-distance CV quantum communication.

中文翻译：

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光纤参量放大器中产生的电信频段强度差异压缩的远距离分布

使用全光纤脉冲双光束源，记录的强度差被压缩 $6.1\pm 0.15\mathrm{D\; b}$对于光纤参量放大器，我们通过实验将脉冲连续变量（CV）量子态分布在很长的距离上。用26 km单模光纤将信号和闲散双光束分开后，测得的强度差噪声仍低于散粒噪声极限2 dB。结果表明，分配过程仅受源自光纤传输损耗的真空噪声的影响。尚未观察到在26 km传输光纤中由声波布里渊散射和拉曼散射贡献的额外噪声。该研究对于研究长距离CV量子通信是有益的。