Matías R. Bolaños

Quantum Random Number Generators (QRNGs) are essential components for modern cryptography, as they are a practical source of true randomness, without which the security of such protocols cannot be guaranteed. Among the proposed schemes, Semi-Device-Independent QRNGs (SDI-QRNGs) based on photon-number constraints offer an appealing balance of security, speed, and experimental simplicity, but demonstrations have so far focused mainly on binary encoding and conditional min‑entropy certification. In this work, we report the first experimental implementation of a Continuous‑Variable SDI‑QRNG in a prepare‑and‑measure configuration building on the SDP‑based (Semi-Definite Programming) framework of Ref.~\cite{carceller2025}. This approach allows us to directly lower‑bound the conditional Shannon entropy, employ more complex modulation formats, and apply entropy‑accumulation techniques beyond the i.i.d. assumption. The experiment combines a low-loss integrated photonic heterodyne receiver with a simple transmitter built from commercial components, generating coherent‑state Quadrature-Phase-Shift-Keying (QPSK) modulation, to preserve experimental practicality while enabling high‑speed operation.

We report, to the best of our knowledge, the first experimental demonstration of wavelength-division multiplexing between independent continuous-variable (CV) and discrete-variable (DV) quantum key distribution (QKD) systems operating simultaneously on the same optical link. We validate coexistence over a fiber and a daylight free-space channel, benchmarking the Secret Key Rate (SKR) versus channel attenuation while both systems operate simultaneously. We observe the expected CV-DV complementarity, with CV-QKD providing higher SKR at low loss and DV-QKD becoming advantageous in the high-loss regime. In free-space daylight, both systems sustain Mbit/s key rates under atmospheric fluctuations. In all scenarios analyzed, simultaneous operation introduces negligible multiplexing-induced penalty. These results provide a validation of hybrid CV-DV architectures for heterogeneous quantum communication infrastructures, where high-throughput metropolitan users and long-reach links can be simultaneously served on the same physical channel.