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[IEEE 2018 IEEE 7th Data Driven Control and Learning Systems Conference (DDCLS) - Enshi (2018.5.25-2018.5.27)] 2018 IEEE 7th Data Driven Control and Learning Systems Conference (DDCLS) - Quantum Noise Protection via Weak Measurement for Quantum Mixed States
摘要： Due to the interaction with the environment, a quantum state is often affected by the different types of noises which becomes to one of the biggest problems for practical quantum computation. We study the possibility of protecting the mixed state of a quantum system that goes through noise by weak measurements and control operations. The aim is to find the optimal measurement strength and control operations and make the input and output states as close as possible. We show that our scheme can effectively protect arbitrary mixed states against typical types of noise sources: amplitude damping, phase damping and amplitude-phase damping. The optimal measurement and control operators are deduced in different bases of the Bloch sphere to find the best control scheme for each type of noise. The effectiveness of our control scheme is demonstrated by simulation results.
关键词： quantum system control,Open quantum system,optimal noise protection,weak measurement
更新于2025-09-23 15:23:52
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Electron Transport Properties of Graphene-Based Quantum Wires
摘要： We study the electronic transport in quantum wire structures made of graphene. By using the nonequilibrium Green function method, the transmission is studied for varies sizes samples. Our results show that the transmission sensitive depends on the size of the system and exhibits fluctuations due to the mismating of propagating modes between the central region and the leads. The number of resonant transmission peaks increases with the increase of length of the wire, while the width of the leads mainly affect the transmission in the region of low energy. A central energy gap in the transmission spectrum is more likely to appear in the quantum wire system than in the uniform armchair graphene nanoribbons. Moreover, the energy gap can be widened for a certain size of the quantum wire system by changing the width of the leads. These results may have potential applications in designing graphene-based devices.
关键词： graphene,quantum wire,transmission
更新于2025-09-23 15:23:52
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Soliton slow light for closed loop quantum systems
摘要： This paper describes the dynamics of solitonic pulse propagation in a closed loop quantum system comprised of five atomic energy levels. Although the propagation of an intense probe pulse suffers losses and broadening in linear regime, there exist specific conditions where the probe pulse is found to become robust during its propagation. We attribute this regime to the formation of an optical soliton with a slow group velocity because of the balance between the dispersion and Kerr optical nonlinearity. Results obtained are based on the theoretical model using the coupled Maxwell-Bloch equations for the nonlinear propagation.
关键词： Optical solitons,Kerr nonlinearity,Nonlinear pulse propagation,Closed-loop quantum system
更新于2025-09-23 15:23:52
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Molecular structure, NBO analysis, ?rst hyper polarizability, and homo-lumo studies of π-extended tetrathiafulvalene (EXTTF) derivatives connected to π-nitro phenyl by density functional method
摘要： In these study we have been obtained the structural properties of (exTTF) derivatives 1-4 by using B3LYP/6-31G(d,p) of Density Functional Theory (DFT) utilizing Becke three exchange functional and Lee Yang Paar correlation functional. The calculation of first hyperpolarizability shows that the molecules are attractive molecules for future applications in non-linear optics. Molecular electrostatic potential (MEP) at a point in the space around a molecule gives an indication of the net electrostatic effect produced at that point by the total charge distribution of the molecule. The calculated HOMO and LUMO energies show that charge transfer occurs within these molecules.
关键词： Density Functional Theory,Quantum Chemical Calculations,Computational Chemistry,Electronic Structure,Tetrathiafulvalenes
更新于2025-09-23 15:23:52
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High Quantum Yield Single-Band Green Upconversion in La <sub/>2</sub> O <sub/>3</sub> :Yb <sup>3+</sup> , Ho <sup>3+</sup> Microcrystals for Anticounterfeiting and Plastic Recycling
摘要： Single-band green upconversion (UC) with high green purity and color stability is urgently required for plastic recycling and anticounterfeiting. However, it is very difficult to obtain single-band green emission for benchmark Yb3+/Er3+ activated UC materials (such as NaYF4:Yb3+,Er3+) due to the strong accompanying red UC. Herein, highly efficient and stable single-band green UC is reported in La2O3:Yb3+/Ho3+ (LYH) microcrystals with record high absolute UC quantum yield (UCQY) of 2.6% for single-band green UC. LYH yields pure green UC with large and stable intensity ratio, IGreen/IRed ≈ 18. LYH presents not only higher UCQY for a single-band green UC but also much more pure and stable green UC than the benchmark UC materials such as NaYF4:Yb3+,Er3+ and Gd2O2S:Yb3+,Er3+. These results suggest that the newly developed LYH can, in principle, be promising for anticounterfeiting and plastic recycling. Its proof-of-concept is demonstrated as a security label based on a transparent institute logo.
关键词： anticounterfeiting,high UC quantum yield,plastic recycling,upconversion materials,pure green UC
更新于2025-09-23 15:23:52
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Highly Luminescent Nitrogen-Doped Carbon Dots as “Turn-On” Fluorescence Probe for Selective Detection of Melamine
摘要： In our work, a new and simple method for selective detection of melamine is established by developing a "turn-on" fluorescence probe based on nitrogen-doped carbon dots (N-CQDs). The N-CQDs have been facilely prepared by one-step simple hydrothermal reaction and it is highly luminescent that with 51% fluorescent quantum yield. In this sensor, the fluorescent intensity of N-CQDs was found to be efficient quenched by Fe3+, upon addition of melamine the fluorescent intensity of N-CQDs-Fe3+ could gradually recover, which may because of the competitive combination of Fe3+ and melamine leading to the departure of Fe3+ from the N-CQDs' surface. Under optimum conditions, the fluorescence intensity has a good liner relationship with melamine in the range of 2.0 to 290 μM. The probe displayed good sensitivity toward melamine with a lower detection limit of 0.67 μM. In addition, this fluorescence probe has been used for the analysis of milk samples, demonstrating the fluorescence probe has potential application in the detection of melamine.
关键词： selective detection,turn-on fluorescence probe,melamine,carbon quantum dot
更新于2025-09-23 15:23:52
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Quantum encryption and generalized Shannon impossibility
摘要： The famous Shannon impossibility result says that any encryption scheme with perfect secrecy requires a secret key at least as long as the message. In this paper we provide its quantum analogue with imperfect secrecy and imperfect correctness. We also give a systematic study of information-theoretically secure quantum encryption with two secrecy definitions. We show that the weaker one implies the stronger but with a security loss in d, where d is the dimension of the encrypted quantum system. This is good enough if the target secrecy error is of o(d?1).
关键词： Quantum one-time pad,Shannon impossibility,Information-theoretic security,Key length
更新于2025-09-23 15:23:52
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Quantum Dialogue Based on Entanglement Swapping and Hadamard Operation via Cavity QED
摘要： A quantum dialogue scheme based on entanglement swapping and Hadamard operation via cavity QED is proposed, which effectively uses the evolution law of atom in cavity QED. The proposed scheme uses Bell states and GHZ states as quantum resource and only needs single-atom measurements. The proposed scheme is secure against active attacks from an eavesdropper and can transmit 4 secret bits per round communication.
关键词： Entanglement swapping,Hadamard operation,Quantum dialogue,Cavity QED
更新于2025-09-23 15:23:52
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Pairwise nonclassical correlations for superposition of Dicke states via local quantum uncertainty and trace distance discord
摘要： The pairwise nonclassical correlations for two-qubit states, extracted from multi-qubit system with exchange symmetry and parity, are quanti?ed by local quantum uncertainty and trace distance discord. The explicit expressions of local quantum uncertainty and geometric trace distance discord for Dicke states and their superpositions are given. A comparison between the two quantum correlations quanti?ers is discussed.
关键词： Pairwise nonclassical correlations,Trace distance discord,Dicke states,Local quantum uncertainty
更新于2025-09-23 15:23:52
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Photochemical multivariate curve resolution models for the investigation of photochromic systems under continuous irradiation
摘要： We propose a multivariate curve resolution approach for the investigation of photochromic systems using UV-Visible spectroscopy. The incorporation of photochemical hard-models as constraints in multivariate curve resolution alternating least squares (MCR-ALS) allows extracting reaction quantum yields in situations where a complete knowledge of the system is not available. We apply this approach to the study of the photochromism of CMTE (cis-1,2-dicyano-1,2-bis(2,4,5-trimethyl-3-thienyl)ethene) under continuous monochromatic irradiation. The mechanism, involving 3 species and 2 reversible reactions, is written and translated into a kinetic constraint that can be applied to the concentration profiles within ALS. First, ambiguity of the solution obtained for photochemical model(s) is calculated and discussed for single set analysis. Multiset analysis is then proposed combining data obtained under different irradiation wavelengths to provide more reliable results. Finally, the photochemical reactivity of CMTE is widely unraveled, and some description of the mechanism observed under irradiation at 365 nm is given.
关键词： Multivariate curve resolution,Quantum yield,Hard-soft modelling,Parameter ambiguity,Photochemical reaction
更新于2025-09-23 15:23:52