Deep Reinforcement Learning for IRS-Assisted UAV Covert Communications

Covert communications can hide the existence of a transmission from the transmitter to receiver.This paper considers an intelligent reflecting surface(IRS)assisted unmanned aerial vehicle(UAV)covert communication system.It was inspired by the high-dimensional data processing and decisionmaking capabilities of the deep reinforcement learning(DRL)algorithm.In order to improve the covert communication performance,an UAV 3D trajectory and IRS phase optimization algorithm based on double deep Q network(TAP-DDQN)is proposed.The simulations show that TAP-DDQN can significantly improve the covert performance of the IRS-assisted UAV covert communication system,compared with benchmark solutions.

Four-stage cascaded variable optical attenuator with large attenuation range for quantum key distribution

A four-stage cascaded variable optical attenuator(VOA)with a large attenuation range is presented.The VOA is based on a Mach–Zehnder interferometer(MZI)and fabricated in a silica-based planar lightwave circuit(PLC)platform.The thermo-optic effect is used to achieve intensity modulation.The measured maximum attenuation of the four-stage cascaded VOA is 88.38 d B.The chip is also tested in a quantum key distribution(QKD)system to generate signal and decoy states.The mean photon number after attenuation of the four-stage cascaded VOA is less than 0.1,which can meet the requirement of QKD.

Predicting stability of integrated circuit test equipment using upper side boundary values of normal distribution

In response to the growing complexity and performance of integrated circuit(IC),there is an urgent need to enhance the testing and stability of IC test equipment.A method was proposed to predict equipment stability using the upper side boundary value of normal distribution.Initially,the K-means clustering algorithm classifies and analyzes sample data.The accuracy of this boundary value is compared under two common confidence levels to select the optimal threshold.A range is then defined to categorize unqualified test data.Through experimental verification,the method achieves the purpose of measuring the stability of qualitative IC equipment through a deterministic threshold value and judging the stability of the equipment by comparing the number of unqualified data with the threshold value,which realizes the goal of long-term operation monitoring and stability analysis of IC test equipment.

Quenching Fluorescence of Quantum Dots by Using Gold Nanocrystals in Quantum and Classical Size Regime

This paper investigates the factors which can influence the quenching effect from the perspective of energy transfer.The quenched fluorescence of the Cd Se semiconductor quantum dots(SQDs)by using plasmonic Au nanocrystals(p-AuNCs)and molecule-like Au nanocrystals(m-AuNCs)in aqueous suspensions and spin-coated films is comparatively investigated.In the aqueous suspensions,the p-AuNCs have larger quenching effect than the m-AuNCs.In the spin-coated films,the p-AuNCs and m-AuNCs have comparable quenching factor.Furthermore,the experiments show that the p-AuNCs simultaneously enhance the radiative and nonradiative rates.But the m-Au NCs only enhance the nonradiative rate of the SQDs,which reveals the difference of quenching process between the p-AuNCs and m-AuNCs.This result of the research has guiding significance for the detection technique based on the fluorescence quenching.

Dynamical-corrected nonadiabatic geometric quantum computation

Recently,nonadiabatic geometric quantum computation has been received great attentions,due to its fast operation and intrinsic error resilience.However,compared with the corresponding dynamical gates,the robustness of implemented nonadiabatic geometric gates based on the conventional single-loop geometric scheme still has the same order of magnitude due to the requirement of strict multi-segment geometric controls,and the inherent geometric fault-tolerance characteristic is not fully explored.Here,we present an effective geometric scheme combined with a general dynamical-corrected technique,with which the super-robust nonadiabatic geometric quantum gates can be constructed over the conventional single-loop geometric and two-loop composite-pulse geometric strategies,in terms of resisting the systematic error,i.e.,σ_(x)error.In addition,combined with the decoherence-free subspace(DFS)coding,the resulting geometric gates can also effectively suppress theσ_(z)error caused by the collective dephasing.Notably,our protocol is a general one with simple experimental setups,which can be potentially implemented in different quantum systems,such as Rydberg atoms,trapped ions and superconducting qubits.These results indicate that our scheme represents a promising way to explore large-scale fault-tolerant quantum computation.