What is Quantum Cryptography?
According to the quantum theory, light is an electromagnetic wave. It is made up of a lot of particles known as photons, each photon has a specific energy hf and a wavelength c/f. Recall that light has a pair of electric and magnetic fields that are perpendicular to each other. If the electric field component of a beam of light vibrates along a single direction then the beam of light is said to be polarized in that direction.
Polarized photons can be created by passing a normal beam of light through a filter set for a specific angle of polarization. A photon incident on the filter will either pass through it or will be blocked. If the photon emerges it will be aligned to the angle of the filter regardless of its initial polarization angle of the filter regardless of its initial polarization.