Highspeed Polarization Preparation Scheme for Quantum Key Distribution for Visible Light

Polarization is widely used as a degree of freedom in which the quantum states are encoded for free-space quantum key distribution (QKD). However, a significant challenge in the visible wavelength range is the absence of fast polarization modulators comparable to those available for telecom wavelengths. Nonetheless, visible wavelengths offer superior performance under daylight conditions when an appropriate Fraunhofer line is utilized [1].