A new model analysis of the third harmonic voltage in inductive measurement for critical current density of superconducting films＊

The critical current density Jc is one of the most important parameters of high temperature superconducting films in superconducting applications, such as superconducting filter and superconducting Josephson devices. This paper presents a new model to describe inhomogeneous current distribution throughout the thickness of superconducting films applying magnetic field by solving the differential equation derived from Maxwell equation and the second London equation. Using this model, it accurately calculates the inductive third-harmonic voltage when the film applying magnetic field with the inductive measurement for Jc. The theoretic curve is consistent with the experimental results about measuring superconducting film, especially when the third-harmonic voltage just exceeds zero. The Jc value of superconducting films determined by the inductive method is also compared with results raeasured by four-probe transport method. The agreements between inductive method and transport method are very good.

Design of two-dimensional elliptically cylindrical invisible cloaks with multiple regions

Two-dimensional （2D） elliptically cylindrical invisible cloaks with multiple regions are designed based on the trans-formation optics and the complementary media theory. Multiple invisible cloak regions can be obtained by properly using the compressed or folded transformation in each space layer. The constitutive parameter tensor expressions for each re- gion have been obtained. The results of full wave simulations by using finite element software confirm the validity of the constitutive parameter tensor expressions. In addition, the parameters are relatively easier to realize.

Topological phase transitions driven by next-nearest-neighbor hopping in noncentrosymmetric cold Fermi gases

We investigate the topological phase marked by the Thouless–Kohmoto–Nightingale–Nijs（TKNN） number and the phase transitions driven by the next nearest neighbor（NNN） hopping in noncentrosymmetric cold Fermi gases, both spinsinglet pairing and spin-triplet pairing are considered. There exists a critical t＇c for the NNN hopping, at which the quantum phase transition occurs, and the system changes from an Abelian（non-Abelian） phase to a non-Abelian（Abelian） one. By numerically diagonalizing the Hamiltonian in the real space, the energy spectra with edge states for different topological phases and the Majorana zero modes are discussed. Although the spin-triplet pairing does not contribute to the gap closing and the phase diagram, it induces gapless states in the presence of a magnetic field, and the TKNN number in this region is still zero.

Locality Violation with Spin-Type W States without Using Inequalities

Using even and odd coherent states, we define a new state, which is called the spin-type W state. With the spin-type W states, we provide a new scheme for testing fundamental aspects of quantum mechanics and refuting local hidden variable theory without using inequalities. Finally, a scheme for preparing the spin-type W states, and discussion of experimental possibility and the effect of the measurement on physical observables due to a close orthogonality of the two coherent states are given.

Unconventional Geometric Phase-Shift Gates Based on Superconducting Quantum Interference Devices Coupled to a Single-Mode Cavity

We present a scheme to realize geometric phase-shift gate for two superconducting quantum interference device （SQUID） qubits coupled to a single-mode microwave field. The geometric phase-shift gate operation is performed in two lower flux states, and the excited state [2〉 would not participate in the procedure. The SQUIDs undergo no transitions during the gate operation. Thus, the docoherence due to energy spontaneous emission based on the levels of SQUIDs are suppressed. The gate is insensitive to the cavity decay throughout the operation since the cavity mode is displaced along a circle in the phase space, acquiring a phase conditional upon the two lower flux states of the SQUID qubits, and the cavity mode is still in the original vacuum state. Based on the SQUID qubits interacting with the cavity mode, our proposed approach may open promising prospects for quantum iogic in SQUID-system.

A high-precision system of fiber Bragg grating temperature sensing demodulation based on light power detection

A system of fiber Bragg grating(FBG)temperature sensing demodulation based on light power detection is proposed in this paper.Compared with the traditional demodulation method based on wavelength scanning,light power detection is more direct and avoids the use of spectrometer.Moreover,the light power in the system is converted into the electrical signal by the receiver optical subassembly(ROSA)and converted to the digital signal.The micro controller unit(MCU)processes the digital signal to realize the real-time temperature monitoring,which avoids the use of optical power meter(OPM).With the advantages of simple structure and low cost,the system is portable and practical.The experimental results show that the linearity coefficients R-square between light power and the sampling voltage are 0.99908 and 0.99893 in the temperature range from 10°C to 85°C,respectively.According to the results,the proved sensor has a repeatability error of 1%,a linearity error of 1.35%,and a hysteresis error of 0.7%,which indicates that the system is of high stability and high precision.The experimental results are consistent with the theory,which verifies the system’s feasibility.

An all-dielectric chiral metasurface with circular dichroism and asymmetric transmission characteristics

This paper designs an all-dielectric metasurface with tunable chiral properties in the near-infrared range,whose working wavelength is 1250-2200 nm.The metasurface exhibits circular dichroism(CD)and asymmetric transmission(AT)characteristics for circularly polarized light.The metasurface is a double-layer structure composed of Ge_(2)Sb_(2)Se_(4)Te_(1)(GSST).

A high-drop hole-type photonic crystal add-drop filter

Based on the effect of total internal reflection(TIR)and photonic band gap,a new type of hexagonal-lattice hole-type silicon photonic crystal add-drop filter is proposed with a large circular hole as inner ring.The single mode operation is realized by compressing the two rows of photonic crystal above and below the line defect waveguide.Two-dimensional(2D)finite-difference time-domain(FDTD)method is then applied to investigate the impacts of side length of inner ring and coupling strength on its drop efficiency.It is also fairly compared with the traditional inner ring structure composed of hexagonal-lattice holes.The results show that the proposed structure can offer higher spectral selectivity than the traditional one.Two channel wavelengths of 1.425μm and 1.45μm can be simultaneously dropped at corresponding ports with drop efficiency of more than 90%and quality factor of 900 in the proposed configuration when the width of bus waveguide,the side length of inner ring and the coupling strength are 0.8 3 a,4a and 0,respectively,where a is the lattice constant.