Observation of Non-Hermitian Quantum Correlation Criterion in Mesoscopic Optomechanical System

Although many quantum correlation criteria have been proposed successively in recent years, it is still an open question how to observe these criteria with the non–Hermitian terms in themselves. We propose an indirect scheme in this paper to observe non-Hermitian criteria and to judge whether or not quantum correlation exists in the system even though the expectation value measurement of non-Hermitian operator is invalid in quantum mechanics system. Our idea is to establish a critical state of mesoscopic oscillator under mean–field approximation, and the oscillator state will take place transition when the quantum correlation destroys the mean–field approximation. The non–Hermitian measurement will replace the position measurement in this process and it can be seen as a non–destructive detection. We give an example to explain this idea in a designed mesoscopic optomechanical system.     

An Efficient Quantum Private Comparison of Equality over Collective-Noise Channels

This article proposes a collective-noise resistant QPC protocol with the help of an almostdishonest third party (TP) who may try to perform any sort of attacks to derive participants’ private secrets except colluding with any participant. The proposed scheme has some considerable advantages over the state-of-the-art QPC protocols over collective-noise channels, where it does not require any pre-shared key between the participants (Alice and Bob). Nevertheless, the proposed scheme can resist Trojan horse attacks without consuming half of the transmitted qubits and any additional equipment (wavelength filter and PNS) support. As a consequence, the proposed QPC protocol can guarantee higher qubit efficiency as compared to the others over collective noise channels.     

Controlled Dense Coding Using the Maximal Slice States

In this paper we investigate the controlled dense coding with the maximal slice states. Three schemes are presented. Our schemes employ the maximal slice states as quantum channel, which consists of the tripartite entangled state from the first party(Alice), the second party(Bob), the third party(Cliff). The supervisor(Cliff) can supervises and controls the channel between Alice and Bob via measurement. Through carrying out local von Neumann measurement, controlled-NOT operation and positive operator-valued measure(POVM), and introducing an auxiliary particle, we can obtain the success probability of dense coding. It is shown that the success probability of information transmitted from Alice to Bob is usually less than one. The average amount of information for each scheme is calculated in detail. These results offer deeper insight into quantum dense coding via quantum channels of partially entangled states.     

Even and Odd Charge Coherent States: Higher-Order Nonclassical Properties and Generation Scheme

We examine the higher-order nonclassical properties of the even and odd charge coherent states as well as proposing a scheme to generate these states whose modes can freely travel in open space. We show that the even and odd charge coherent states exhibit both higher-order antibunching and higher-order squeezing. While the two-mode higher-order antibunching occurs in any order and essentially depends on the charge number, the two-mode higher-order squeezing appears only in the even orders. We also prove that these states are genuinely entangled, and they can be generated by means of cross-Kerr media, beam splitters, phase shifts and threshold detectors. We find that the fidelity and the corresponding success probability to generate these states are dependent on the correlative parameters.     

Studies on Structural,Morphological and Optical Properties of Chemically Deposited CdS<Subscript>1-x</Subscript>Se<Subscript>x</Subscript> Thin Films

The thin films of CdS_1-xSe_x were successfully deposited over glass substrates by chemical bath deposition technique. Cadmium acetate, thiourea and sodium selenosulfate were used as source materials for Cd²⁺, S^2? and Se^2? ions, while 2-mercaptoethanol was used as capping agent. The various deposition conditions such as precursor concentration, deposition temperature, pH and deposition time were optimized for the deposition of CdS_1-xSe_x thin films of good quality and the films were annealed at 200° and 300 °C. The structural, morphological, chemical and optical properties were examined by various characterization techniques and discussed in detail. The optical band gap of CdS_1-xSe_x thin film samples were estimated and found in the range from 2.11 to 1.79 eV for as-deposited and annealed thin films.     

Synthesis and Properties of a Novel FRET-Based Ratiometric Fluorescent Sensor for Cu<Superscript>2+</Superscript>

A novel FRET-based probe LS3 was designed and synthesized. As expected, it exhibited high selectivity and sensitivity for detecting Cu²⁺ over other commonly coexistent metal ions. The detection limit was measured to be 0.0423 μM for Cu²⁺, which can meet the selective requirements for practical application. In addition, the newly synthesized compound 3a/b have potential value of further synthesizing more analogous FRET-based probes.     

Synthesis of 2-Mercaptonicotinic Acid-Capped CdSe Quantum Dots and its Application to Spectrofluorometric Determination of Cr(VI) in Water Samples

The CdSe quantum dots (QDs) capped with 2-mercaptonicotinic acid (H₂MN) were prepared through a controllable process at 80 °C. The prepared QDs were characterized by XRD, TEM, IR, UV–Vis and fluorescence (FL) techniques. It was found that the QDs were nearly mono-disperse with the diameters in the range of 8–10 nm. These QDs are capable to exhibit strong FL even in concentrated acidic media. They exhibit an enhanced fluorescence in the presence of Cr(VI), which was used for the determination of Cr(VI) in water samples. The linear range was found to be 1?×?10^?7–6.0?×?10^?6 M with the RSD and DL of 0.92 % and 5?×?10^?8 M, respectively. Except that Ca²⁺ and Fe³⁺ which can be eliminated through a simple precipitation process, the other co-existent ions present in natural water were not interfered. The recoveries obtained for the added amounts of Cr(VI) were in the range of 96.9–103.2 %, which denote on application of the method, satisfactorily.     

Steady State and Time Resolved Spectroscopic Study of CdSe and CdSe/ZnS QDs:FRET Approach

This article highlights some physical studies on the relaxation dynamics and Förster resonance energy transfer (FRET) of semiconductor quantum dots (QDs) to proximal dye molecule and the way these phenomena change with core to core-shell QD is discussed. Efforts to understand the optical and carrier relaxation dynamics of CdSe and CdSe/ZnS QDs are made by using absorption, steady-state fluorescence and time-resolved fluorescence (TCSPC) techniques. Steady-state as well as time-resolved fluorescence measurements were employed to evaluate the QD PL quenching induced by the proximal Rhodamine 101 dye molecule and to examine the influence of deep trap states on energy transfer efficiency. The FRET parameters such as spectral overlap, Förster distance, intermolecular distance for each donor-acceptor pair are determined and variation of these parameters from core to core-shell QD is discussed.     

A Turn-on and Reversible Fluorescence Sensor for Zinc Ion Based on 4,5-Diazafluorene Schiff Base

A new 4,5-diazafluorene-based fluorescent chemosensor has been synthesized by Schiff base condensation of 9,9-bis(3,5-dimethyl-4-aminophenyl)-4,5-diazafluorene with salicylaldehyde. The interaction of Schiff base with different metal ions has been studied over photofluorescent spectra. The results showed that Schiff base exhibited 194-fold enhancements in fluorescence at 465 nm after Zn²⁺ ions. Such fluorescent responses could be detected by naked eye under UV-lamp. The complex solution (L-Zn²⁺) exhibited reversibility with EDTA.     

Inequalities for Purity Parameters of Multiqudit and Single-Qudit States

We analyze the recently found inequality for eigenvalues of the density matrix and purity parameters describing either a bipartite-system state or a single-qudit state. We rewrite the Minkowski-type trace inequality for the density matrices of the qudit states in terms of the purity parameters and discuss the properties of the inequality obtained, paying special attention to the X-states of two qubits and a single qudit. Also we study the relation of the purity inequalities obtained with the entanglement.