- Discrete Variable QKD: this is the most common and oldest protocol (BB84 or EK91 protocol) and is originally based on the transmission of information encoded on the physical properties of a single photon. The generation of a true single photon source is both difficult and resource intensive.
- Continuous Variable QKD: with this next generation QKD approach, information is encoded onto the amplitude and phase quadrature of a bright coherent laser and is neither limited by single-photon generation nor single-photon detection techniques. Because of this, standard optical network components can be leveraged, reducing the costs considerably.
