Peter Gleißner | Searcharxiv

arXiv2026

Chip-Scale Transmitter Module for Real-Time Continuous-Variable QKD

Continuous-variable quantum key distribution (CV-QKD) enables secure communication over standard telecom infrastructure, but scaling is stalled by bulky, discrete optical hardware. We address this bottleneck by demonstrating a real-time CV-QKD system driven by a chip-scale hybrid transmitter using commercial telecom components. Combining a micro-optic external-cavity laser with a monolithic photonic integrated IQ modulator we enable secure secret-key generation over 102 km of optical fiber while reducing optical volume by 95% relative to the commercial discrete-component counterpart. Moreover, real-time operation overcomes offline post-processing bottlenecks of experimental setups. This work bridges laboratory demonstrations and field-deployable technology for cost-effective quantum networks.

quant-ph↗

arXiv2023

Restricted Global Optimization for QAOA

The Quantum Approximate Optimization Algorithm (QAOA) has emerged as a promising variational quantum algorithm for addressing NP hard combinatorial optimization problems. However, a significant limitation lies in optimizing its classical parameters, which is in itself an NP hard problem. To circumvent this obstacle, initialization heuristics, enhanced problem encodings and beneficial problem scalings have been proposed. While such strategies further improve QAOA's performance, their remaining problem is the sole utilization of local optimizers. We show that local optimization methods are inherently inadequate within the complex cost landscape of QAOA. Instead, global optimization techniques greatly improve QAOA's performance across diverse problem instances. While global optimization generally requires high numbers of function evaluations, we demonstrate how restricted global optimizers still show better performance without requiring an exceeding amount of function evaluations.

quant-ph↗