Jayanth Ramakrishnan

Continuous-variable quantum key distribution (CVQKD) enables practical quantum communication using standard telecommunication technologies. Unidimensional CVQKD (UD-CVQKD) reduces experimental complexity by encoding information in a single quadrature of optical fields, unlike conventional two-quadrature implementations. In this work, we experimentally demonstrate a free-space Gaussian modulated UD-CVQKD system using polarized coherent states. The security performance is analyzed under both trusted and untrusted detector noise models. Positive key rates are obtained for both models, achieving up to 0.79 bits/pulse (trusted detector) and 0.68 bits/pulse (untrusted detector) under optimal conditions. The dependence of system parameters on Alice’s modulation variance is also experimentally investigated, showing a decrease in key rate with increasing modulation variance.