Quantum phase diagram for homogeneous Bose‐Einstein condensate

We calculate the quantum phase transition for a homogeneous Bose gas in the plane of s‐wave scattering length a_s and temperature T. This is done by improving a one‐loop result near the interaction‐free Bose‐Einstein critical temperature T_c⁽⁰⁾ with the help of recent high‐loop results on the shift of the critical temperature due to a weak atomic repulsion based on variational perturbation theory. The quantum phase diagram shows a nose above T_c⁽⁰⁾, so that we predict the existence of a reentrant transition above T_c⁽⁰⁾, where an increasing repulsion leads to the formation of a condensate.     

Solitons and intrinsic localized modes in a one-dimensional antiferromagnetic chain

By use of the Hartree approximation and the method of multiple scales, we investigate quantum solitons and intrinsic localized modes in a one-dimensional antiferromagnetic chain. It is shown that there exist solitons of two different quantum frequency bands: i.e., magnetic optical solitons and acoustic solitons. At the boundary of the Brillouin zone, these solitons become quantum intrinsic localized modes: their quantum eigenfrequencies are below the bottom of the harmonic optical frequency band and above the top of the harmonic acoustic frequency band.     

基于光环路正交频分多址无源光网络的光拍频噪声避免方案及性能仿真(英文)

在正交频分多址无源光网络上行传输中,不同光网络单元的上行信号如果采用相同波长的不同激光器将会产生光拍频噪声,使得光网络单元的无色性难以实现.本文以正交频分多址无源光网络为研究对象,通过对系统结构的研究和相关公式的推导,分析了信号上行传输中光拍频噪声的产生原因和避免方式.针对下行发送上行载波结合光线路终端相干接收的光拍频噪声避免方案进行了仿真研究.分析了系统的抗色散方案以及色散累积和训练序列长度对系统性能的影响,给出了优化的参数设置,为系统实际应用提供了理论参考.     

基于脉冲石英增强光声光谱的中红外超高灵敏CO探测

发展了一种超高灵敏的CO痕量气体测量装置,该装置采用4.65μm脉冲式中红外外腔量子级联激光器作为激发光源,结合石英增强光声光谱技术,对2135~2225cm-1之间的CO基频振动光谱带R支进行连续光谱扫描。水被加入到被测气体中,以加快较慢的CO分子振动-平动弛豫率。在锁相放大器时间常数为3ms,激光器占空比和扫描速率为50%和18cm-1/s时,获得的最小探测极限为4.6×10-8(体积分数),与之对应的归一化噪声等效吸收系数为1.07×10-8 cm-1 W/Hz。     

Uncertainty and Certainty Relations for Pauli Observables in Terms of Renyi Entropies of Order α∈ （0; 1]

We obtain uncertainty and certainty relations of state-independent form for the three Paufi observables with use of the Renyi entropies of order α∈ （0; 1]. It is shown that these entropic bounds are tight in the sense that they are always reached with certain pure states. A new result is the condition for equality in Renyi-entropy uncertainty relations for the Pauli observables. Upper entropic bounds in the pure-state case are also novel. Combining the presented bounds leads to a band, in which the rescaled average Renyi a-entropy ranges for a pure measured state. A width of this band is compared with the Tsallis formulation derived previously.     

Energy spectrum of multi-radiation of X-rays in a low energy Mather-type plasma focus device

The multi-radiation of X-rays was investigated with special attention to their energy spectrum in a Mather-type plasma focus device （operated with argon gas）. The analysis is based on the effect of anomalous resistances. To study the energy spectrum, a four-channel diode X-ray spectrometer was used along with a special set of filters. The filters were suitable for detection of medium range X-rays as well as hard X-rays with energy exceeding 30 keV. The results indicate that the anomalous resistivity effect during the post pinch phase may cause multi-radiation of X-rays with a total duration of 300 ± 50 ns. The significant contribution of Cu-Kα was due to the medium range X-rays, nonetheless, hard X-rays with energies greater than 15 keV also participate in the process. The total emitted X-ray energy in the forms of Cu-K and Cu-K/3 was around 0.14 ± 0.02 （J/Sr） and 0.04 ±0.01 （J/Sr）, respectively. The total energy of the emitted hard X-ray （〉 15 keV） was around 0.12± 0.02 （J/Sr）.     

New 3-mode bosonic operator realization of SU（2） Lie algebra： From the point of view of squeezing

We consider the quantum mechanical SU(2) transformation e2λ JzJ± e-2λJz= e±2λJ± as if the meaning of squeezing with e±2λbeing squeezing parameter. By studying SU(2) operators(J±,Jz) from the point of view of squeezing we find that(J±,Jz) can also be realized in terms of 3-mode bosonic operators. Employing this realization, we find the natural representation(the eigenvectors of J+ or J-) of the 3-mode squeezing operator e2λ Jz. The idea of considering quantum SU(2) transformation as if squeezing is liable for us to obtain the new bosonic operator realization of SU(2) and new squeezing operators.     

Effects of shaded facets on the performance of metal-coated etched diffraction grating demultiplexer

A finite-difference time-domain (FDTD) method combined with a periodic boundary condition is used to analyze the diffraction efficiency of an etched diffraction grating (EDG) demultiplexer coated with a metallic film at the backside. The numerical results show that the diffraction loss is mainly due to the scattering effect of shaded facets of a metal-coated grating at both the polarizations. However, the same shaded facets can produce a higher loss for a TM polarization than that for a TE polarization, which induces a higher polarization dependent loss (PDL) of the demultiplexer.     

PTCDA/P-Si光电探测器欧姆接触层的XPS测试分析

在光电探测器PTCDA/P-Si芯片的有机层表面,成功制作出了比接触电阻为4.5×10-5Ω·cm2的低阻欧姆接触层。利用X射线光电子能谱(XPS)对Al/Ni/ITO的欧姆接触层界面的电子状态进行了测试和分析。结果表明,ITO中的In3d及Sn3d各出现两个分裂能级的谱峰,它们是In和Sn原子处于氧化环境的结合能。Ni2p有两个谱峰Ni2p(1)及Ni2p(2),低结合能位置Ni2p(1)对应于Ni原子被X射线激发产生的谱峰,说明NiITO之间没有发生化学反应,Ni层阻止了Al层被氧化成Al2O3;高结合能Ni2p(2)谱峰说明已形成了Al3Ni冶金相,有利于低阻欧姆接触层的形成。     

In-situ EXAFS study on the thermal decomposition of TiH_2

Thermal decomposition behaviors of TiH_2 powder under a flowing helium atmosphere and in a low vacuum condition have been studied using an in situ EXAFS technique.By an EXAFS analysis containing the multiple scattering paths including H atoms,the changes of the hydrogen stoichiometric ratio and the phase transformation sequence are obtained.The results demonstrate that the initial decomposition temperature is dependent on experimental conditions,which occurs,respectively,at about 300 and 400℃ in a low vacuum condition and under a flowing helium atmosphere.During the decomposition process of TiH_2 in a low vacuum condition,the sample experiences a phase change process:δ(TiH_2)→δ(TiH_x)→δ(TiH_1)+β(TiH_x)→δ(TiH_x)+β(TiH_x)+α(Ti)→β(TiH_x)+α(Ti)→α(Ti)+β(Ti).This study offers a way to detect the structural information of hydrogen.A detailed discussion about the decomposition process of TiH_2 is given in this paper.