Study on continuous variable entanglement of pulsed light

我们研究了产生脉冲光连续变量纠缠的方法，并证明了超越经典极限的量子关联。我们提出并证明了一种利用环形干涉仪稳定地产生正交纠缠光脉冲的方案，并在通信波长产生了纠缠光脉冲，并验证了状态的不可分性。我们通过实验演示了利用连续变量贝尔测量和后处理位移技术来传输单个光脉冲的连续量子变量。实验测得保真度F=0.57±0.03，高于经典无纠缠情况下的保真度(FC=0.5)。在使用高重复频率皮秒脉冲序列的实验中，我们观察到了使用时间整形本机振荡器脉冲的-4.5分贝压缩。量子关联在相隔4米的两个测量点上得到了验证，这足以将两个测量因果地分开。

We have studied methods for creating continuous variable entanglement of pulsed light, and demonstrated quantum correlations beyond the classical limit. We have proposed and demonstrated a scheme to stably generate quadrature-entangled optical pulses using a ring interferometer and generated entangled light pulses at telecommunication wavelength, and verified the inseparability of the states. We experimentally demonstrated transporting continuous quantum variables of individual light pulses by using continuous-variable Bell measurements and post-processing displacement techniques. Fidelity of F=0.57±0.03 was experimentally achieved, which is higher than the bound (Fc=0.5) of the classical case in the absence of entanglement. In the experiments using high-repetition rate picosecond pulse train, we have observed-4.5 dB squeezing using a temporally shaped local oscillator pulse. Quantum correlations were verified at two measurement points separated by a distance of 4 m that is sufficient to causally separate two measurements.