Chen Lirong, Xu Zhongxiao, Zeng Weiqing, Wen Yafei, Li Shujing, Wang Hai
The State Key Laboratory of Quantum Optics and Quantum Optics Devices, Collaborative Innovation Center of Extreme Optics, Institute of Opto-Electronics, Shanxi University, Taiyuan, 030006, People's Republic of China.
Sci Rep. 2016 Sep 26;6:33959. doi: 10.1038/srep33959.
We report an experiment in which long-lived quantum memories for photonic polarization qubits (PPQs) are controllably released into any one of multiple spatially-separate channels. The PPQs are implemented with an arbitrarily-polarized coherent signal light pulses at the single-photon level and are stored in cold atoms by means of electromagnetic-induced-transparency scheme. Reading laser pulses propagating along the direction at a small angle relative to quantum axis are applied to release the stored PPQs into an output channel. By changing the propagating directions of the read laser beam, we controllably release the retrieved PPQs into 7 different photonic output channels, respectively. At a storage time of δt = 5 μs, the least quantum-process fidelity in 7 different output channels is ~89%. At one of the output channels, the measured maximum quantum-process fidelity for the PPQs is 94.2% at storage time of δt = 0.85 ms. At storage time of 6 ms, the quantum-process fidelity is still beyond the bound of 78% to violate the Bell's inequality. The demonstrated controllable release of the stored PPQs may extend the capabilities of the quantum information storage technique.
我们报告了一项实验，其中用于光子偏振量子比特（PPQ）的长寿命量子存储器被可控地释放到多个空间分离通道中的任意一个。PPQ由单光子水平的任意偏振相干信号光脉冲实现，并通过电磁诱导透明方案存储在冷原子中。沿相对于量子轴成小角度方向传播的读取激光脉冲用于将存储的PPQ释放到输出通道。通过改变读取激光束的传播方向，我们分别可控地将检索到的PPQ释放到7个不同的光子输出通道。在存储时间δt = 5 μs时，7个不同输出通道中的最小量子过程保真度约为89%。在其中一个输出通道，在存储时间δt = 0.85 ms时，测量到的PPQ的最大量子过程保真度为94.2%。在存储时间6 ms时，量子过程保真度仍超过78%的界限以违反贝尔不等式。所展示的存储PPQ的可控释放可能会扩展量子信息存储技术的能力。
