Coexistence of multiuser entanglement distribution and classical light in optical fiber network with a semiconductor chip

Building communication links among multiple users in a scalable and robust way is a key objective in achieving large-scale quantum networks. In realistic scenario, noise from the coexisting classical light is inevitable and can ultimately disrupt the entanglement. The previous significant fully connected multiuser entanglement distribution experiments are conducted using dark fiber links and there is no explicit relation between the entanglement degradations induced by classical noise and its error rate. Here we fabricate a semiconductor chip with a high figure-of-merit modal overlap to directly generate broadband polarization entanglement. Our monolithic source maintains polarization entanglement fidelity above 96% for 42 nm bandwidth with a brightness of 1.2*10^7 Hz/mW. We perform a continuously working quantum entanglement distribution among three users coexisting with classical light. Under finite-key analysis, we establish secure keys and enable images encryption as well as quantum secret sharing between users. Our work paves the way for practical multiparty quantum communication with integrated photonic architecture compatible with real-world fiber optical communication network

The Impact of User Behavior on Information Diffusion in D2D Communications: A Discrete Dynamical Model

This paper aims to explore the impact of user behavior on information diffusion in D2D (Device-to-Device) communications. A discrete dynamical model, which combines network metrics and user behaviors, including social relationship, user influence, and interest, is proposed and analyzed. Specifically, combined with social tie and user interest, the success rate of data dissemination between D2D users is described, and the interaction factor, user influence, and stability factor are also defined. Furthermore, the state transition process of user is depicted by a discrete-time Markov chain, and global stability analysis of the proposed model is also performed. Finally, some experiments are examined to illustrate the main results and effectiveness of the proposed model

High-efficiency non-ideal quarter-wavelength Bragg reflection waveguide for photon-pair generation

Quantum light source is a promising resource for quantum-enhanced technologies and tests of quantum mechanics. In the race towards scalable quantum information processing, integrated photonics has recently emerged as a powerful platform. Semiconductor AlGaAs is arising as an outstanding platform due to its strong second-order nonlinearities, direct bandgap, manufacturability and reconfigurability. Here, we conduct an analytical investigation of semiconductor Bragg reflection waveguide (BRW), in which the core layer is surrounded by periodic claddings. A general solution to the mode dispersion equation is deduced independently of whether each cladding layer has an ideal quarter-wavelength thickness or not, and used for the analysis of AlGaAs/GaAs material. Different than before, we propose a novel structure with the core layer having high-index and achieve high modal overlap after full parameter optimization in a BRW slab structure, which can provide a practical way for designing high efficiency devices. The influence of thickness variation on overlap factor and system dispersion as well as biphoton spectral properties generated from type-II spontaneous parametric down conversion are also shown. Our approach can serve as a quick guideline for the design of polarization-entangled sources and contribute to large scale processing devices for practical applications by leveraging the structure’s versatile architecture