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。我们提出并论证了利用环形干涉仪稳定产生正交纠缠光脉冲的方案，并在通信波长上产生了纠缠光脉冲，验证了纠缠态的不可分离性。利用连续变量Bell测量和后处理位移技术，我们在实验上证明了单个光脉冲的连续量子变量的传输。实验上达到了F=0.57±0.03的保真度，这高于在没有纠缠的情况下经典情况下的束缚（Fc=0.5）。在实验中，使用高重复率皮秒脉冲序列，我们已经观察到-4.5分贝压缩使用时间成形本振脉冲。量子相关性在相隔4 m的距离的两个测量点处得到验证，该距离足以因果地分离两个测量。

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.