具有实用价值的纠缠态光源的研制

为获得具有实用价值的纠缠态光源,课题组首先进行了系列高质量全固态连续单频1064 nm和532 nm激光器的研制。研制完成的全固态连续单频1 064 nm激光器的性能指标如下:输出功率达30 W,光光转换效率达37%,7 h内的输出功率波动优于±0.3%,光束质量(M2)优于1.1。同时对激光器1 064 nm/532 nm双波长输出的激光器的噪声进行了研究,其强度和位相噪声均在分析频率4 MHz处达到散粒噪声基准。而且非线性晶体还可以作为噪声抑制装置,对1 064 nm输出激光的强度噪声进行抑制,使其在低频段的驰豫振荡噪声降低40 d B。进行了光通信波段1.55μm和1.34μm全固态连续单频激光器的研制,获得了680 MW的连续单横模1.55μm激光输出以及400 m W的连续单频1.55μm激光输出,1.5 h内输出功率波动优于±1.5%,其强度噪声和位相噪声在分析频率5 MHz处均达到散粒噪声基准;获得了输出功率达9 W的连续单频1.34μm激光输出,光光转换效率达18%。激光器在4小时内的功率稳定性优于±1%,在1 min的频率漂移为8.5 MHz,输出激光的光束质量M2因子为1.03。进行了1.55μm和1.34μm光通信波段连续变量量子纠缠光源的研制,经过优化实验系统,获得了压缩度为5 d B、波长为1.55μm的压缩态光场,压缩度为6.1 d B、波长为1.3μm的压缩态光场;完成了1.08μm连续变量量子纠缠光源样机的研制,纠缠源系统的输出波长为1 080 nm,振幅和位相差起伏方差大于5 d B。设计并研制了双色可调谐连续变量纠缠态产生装置,其中,纠缠光束中的一束波长位于碱金属铷原子的吸收线波段;在实验室建立起一套基于光纤通信器件的远程连续变量量子密钥分发系统平台,实验实现了30 km的四态分离调制连续变量量子密钥分发,有效密钥速率大于1 k B/s。利用光子晶体光纤,制备了接近单模的E波段单光子,实验测得其宣布效率可达86%(修正探测效率后),强度关联函数违背经典光源极限值80倍以上。

To build a practical entanglement light source, a series of high quality lasers have been developed. A cw singlefrequency laser at 1 064 μm has been achieved; the maximum output power is 30 W with an optical-to-optical efficiency of 37%. The power fluctuation is better than ±0.3% during 7 hours. The beam quality is less than 1.1. Both the intensity and the phase noise of laser reach the shot noise limit （SNL） at the analysis frequency of 4 MHz. Meanwhile the nonlinear crystal is also used to suppress the extra noise of laser, a 40 dB reduction in the intensity noise at the resonant relaxation oscillation frequency has been observed. Other all-solid-state CW single-frequency lasers at 1.55 μm and 1.34 μm telecom band have been developed and 400 MW CW single frequency laser output has been achieved with the power fluctuation better than ±1.5% during 1.5 hours. Both the intensity and the phase noise of laser reach the SNL at the analysis frequency of 5 MHz. For the 1.34 μm laser, power up to 9 W was realized with an optical-to-optical efficiency of 18%. The power fluctuation is better than ±1% during 4 hours. The frequency drift is 8.5 MHz in 1 minute. The beam quality factor was measured to be less than 1.03. The continuous variable （CV） quantum entangled sources have been investigated in the 1.55 μm and 1.34 μm telecom band. A 5 dB squeezed light at 1.55 μm and a 6.1 dB squeezed light at 1.3 μm have been obtained. The prototype of CV quantum entangled source at 1.08 μm has been manufactured. More than 5dB of amplitude quadrature sum noise spectrum and phase quadrature difference noise spectrum can be observed. The generating device of two-color tunable continuous-variable entanglement has been designed and manufactured. The wavelength of one entangled beam is located at the absorption lines of alkaline atom Rb. The platform of remote continuous variable quantum key distribution system has been established by the fiber-based communication devices. The four-state separation modulation continuous variable quantum key distribution over 30-km fiber has been realized. The effective key rate is greater than 1 kb/s. The single-photon close to the single mode E-band has been prepared by the photonic crystal fiber. The announced efficiency after the experimental measurement is 86%. The intensity correlation function violates the classical light limit of more than 80 times.