远距离自由空间量子干涉实验研究

Optical quantum interference provides an excellent platform for understanding the key concepts of quantum physics and testing basic problems of quantum mechanics, and plays an important role in quantum information. Especially in quantum communication, quantum teleportation and measurement-device-independent quantum key distribution require quantum interference of two independent photons to perform Bell state measurement. Quantum communication technology has been developed rapidly in the past two decades. Fiber-based inner-city quantum network is now close to practical use. However, limited by the attenuation of the fiber, a global wide-area quantum network relies on free-space channels and space platforms. Due to the instability caused by atmospheric turbulence, quantum interference between independent photon sources in long-distance free-space channels has not been realized yet. This project will improve the stability of single-mode fiber coupling efficiency by using adaptive optics system. Combined with high-precision time synchronization of independent clock and high-precision frequency locking of independent laser, we will realize quantum interference experiment between independent photon source through long-distance free space channel.

光学量子干涉除了为量子物理关键概念的理解和量子力学基本问题检验提供绝佳的平台，也在量子信息的各领域中扮演了重要的角色。尤其是在量子通信中，量子隐形传态、测量设备无关量子密钥分发等都需要对两个独立光子进行量子干涉，从而实现Bell态测量。量子通信技术在近二十年间得到了蓬勃的发展，基于光纤信道的城域量子通信网络已接近实用化。然而，受限于光纤自身的衰减特性，全球化广域量子通信网络必需依赖于自由空间信道和空间平台。由于大气湍流带来的不稳定性，长距离自由空间信道下的独立光源量子干涉至今未能实现。本项目将通过自适应光学系统提高单模光纤耦合效率的稳定性，结合独立时钟的高精度时间同步和独立激光器的高精度频率锁定，实现长距离自由空间信道下的独立光源量子干涉实验研究。

量子干涉是量子态叠加概念的自然结果。当单个光子或光的强度发生干涉时，干涉结果在量子和经典物理的描述中是一样的。但是，当两个或更多的光子之间发生干涉时，干涉结果开始出现反直觉的特性。两个来自独立光源的光子发生干涉，也即HOM干涉，的结果只能通过概率幅的解释来描述。光学量子干涉除了为量子物理关键概念的理解和量子力学基本问题检验提供绝佳的平台，也在量子信息的各领域中扮演了重要的角色。尤其是在量子通信中，量子隐形传态、测量设备无关量子密钥分发等都需要对两个独立光子进行量子干涉，从而实现Bell态测量。本项目通过自适应光学系统提高单模光纤耦合效率的稳定性，结合独立时钟的高精度时间同步和独立激光器的高精度频率锁定，实现了长距离自由空间信道下的独立光源量子干涉实验演示。基于此技术，在19.2km城市内自由空间信道上演示了独立光源的测量设备无关量子密钥分发，为全球化广域量子通信开启了新的可能性。