Quantum key distribution employing geometric rotating of the quantum

Quantum polarisation is an important property that has extensively being used for quantum communication purposes. In this work, initially, the mixture of an unpolarised two-mode state and a two-mode pure state is analysed. Such mixture is controlled by a single parameter, the degree of purity. The quantum polarisation of the twomode mixed state is discussed using quantum Stokes parameters. After, a quantum key distribution set-up using geometric rotating of the quantum polarisation of coherent light pulses is proposed and analysed using both pure and mixed states.