All Optical Processes for Free-Space Quantum Communications

Quantum communication offers new ways to protect and transmit information, however sending quantum states through the free space presents a challenge: atmospheric turbulence can distort the shape of light as it travels, making it difficult to reliably recover the information encoded in the light.

In this talk, an approach will be presented that uses nonlinear optics to automatically correct these distortions. The key idea is to use a process called stimulated parametric down-conversion to create a phase-conjugated copy of the distorted light. In this way, the optical system can compensate for the effects of turbulence without requiring a conventional adaptive-optics system or prior knowledge of the atmospheric conditions.

This approach can be used to improve the transmission of information encoded in different spatial patterns of light, and present theoretical, numerical, and experimental results demonstrating its ability to mitigate turbulence. This work explores a new route toward more robust free-space quantum communication and could help make high-dimensional quantum communication more practical in real-world atmospheric environments.