Continuous-Variable Quantum Communication

Abstract

Gaussian states have risen to a privileged position as a result of their actively pursued experimental discoveries. When Gaussian modulated coherent state quantum key distribution (QKD) with homodyne detection is compared to discrete variable QKD,it has been proven to be a secure method of practical quantum cryptography with great e ciency. I studied theoretically Gaussian modulated continuous variable quantum key distribution in my thesis after introducing basics connected to continuous variable systems. I computed the covariance matrices for the states in order to do additional operations on them. I noticed the di erence in secure key rate and Holevo information in both the cases when Eve is present or absent on the transmission channel. I looked at this development of continuous quantum variables in quantum information by using electromagnetic eld quadrature amplitudes. Finally, I was able to properly manage the protocol with Gaussian states, resulting in secure key distribution between the two sides.