Quantum key distribution enables the generation of an information-theoretically secure secret key between two legitimate parties. When combined with one time pad, one can achieve private communication. Continuous variable quantum key distribution utilizes the quadratures of the quantized light field as the carriers of key information. The key feature is that it has good compatibility with the coherent optical telecommunication technology.

Quantum optomechanics, which investigates the interaction between micro/nano mechanical resonators and light field via radiation pressure, has emerged as a new frontier in quantum optics. Cavity quantum optomechanics combines micro resonators with high fineness cavities, in this case the opto-mechanical interaction can be enhanced significantly. It has potential applications in the fields of fundamental tests of macroscopic quantum physics, ultrasensitive quantum metrology, and quantum information processing, etc.

Entanglement is a unique quantum phenomenon that occurs when each subsystem of a quantum state cannot be described independently of the others. Such kind of states have been widely employed as important resources for quantum information processing, such as quantum communication, quantum computing, and quantum metrology. Quantum interface capable of transferring quantum states between different carrier frequencies is a necessary component for quantum information processing. Such quantum-state-preserving frequency conversion enables seamless connection of quantum devices that operate at different carrier frequencies.