What is the motivation behind quantum key distribution with Continuous variable? Quantum Key Distribution protocol is a technique that allow two parties to share common secret key for cryptographic purpose and defined as being secure, by definition. But I am still wondering: what is the motivation behind quantum key distribution with Continuous variable?
 A: This really comes down to what quantum states you prefer to use.For example if for some reason your noise channel does not affect coherent states that much or you have really good error correcting for them, then you would use continuous variable quantum key distribution. In this case it would be stupid use discrete quantum states and make yourself really vulnerable to noise.
A: There are two main types of Quantum Key distribution (QKD) systems: discrete variable (DV) and continuous variable (CV).
In DV-QKD protocols, information is encoded on properties of single photons, such as the state of polarization. This idea was first presented in the BB84 protocol.
On the other hand, in CV-QKD protocols information is encoded in properties
of the continuous lightwave, such as the quadratures of a coherent state. A simple and mature CV-QKD protocol is GG02.
Advantages of CV-QKD: uses mature optical communications components and avoids single-photon detectors that are costly and complex, and require low temperatures. Thus, CV-QKD proffers a prospect of high secret key rate and presents an easier merging with present telecommunication networks.
