Theoretical study of indirect excitons’ lifetime in coupled AlGaN/GaN quantum wells in the presence of an electrostatic trap

The lifetime of electrostatically trapped indirect excitons in a field-effect structure based on coupled AlGaN/GaN quantum wells has been theoretically studied. Within the plane of a double quantum well, indirect excitons are trapped between the surfaces of the AlGaN/GaN heterostructures and a semitransparent metallic top gate. The trapping mechanism has been assumed to be a combination of the quantum confined Stark effect and local field enhancement. In order to study the trapped exciton lifetime, the binding energy of indirect excitons in coupled quantum wells is calculated by finite difference method in the presence of an electric field. Thus, the lifetime of trapped excitons is computed as a function of well width, AlGaN barrier width, the position of double quantum well in the device and applied voltage.     

Simple Scheme for Realizing the General Conditional Phase Shift Gate and aSimulation of Quantum Fourier Transform in Circuit QED

We propose a theoretical scheme for realizing the generalconditional phase shift gate of charge qubits situated in ahigh-Q superconducting transmission line resonator. Thephase shifting angle can be tuned from 0 to 2π by simplyadjusting the qubit-resonator detuning and the interaction time.Based on this gate proposal, we give a detailed procedure toimplement the three-qubit quantum Fourier transform withcircuit quantum electrodynamics (QED). A careful analysis of thedecoherence sources shows that the algorithm can be achieved with ahigh fidelity using current circuit QED techniques.     

Vacuum-Induced Abelian and Non-Abelian Gauge Potentials in CavityQuantum Electrodynamics

Gauge potential plays an important role in exploring exotic phenomena in the single- and many-body quantum systems. In this paper, we propose a scheme to create both new Abelian and non-Abelian gauge potentials by adiabatically controlling the degenerate Dicke model in cavity quantum electrodynamics. It is shown that a non-Abelian gauge potential is achieved only for a single atom, whereas an Abelianizen diagonal gauge potential is realized for the atomic ensemble. More importantly, two interesting quantum phenomena such as the geometric phase and the magnetic monopole induced by our created gauge potentials are also predicted. The possible physical realization is presented in the macroscopic circuit quantum electrodynamics with the Cooper pair boxes, which act as the artificial two-level atoms controlled by the gate voltage and the external magnetic flux.     

Quantum Information Splitting of an Arbitrary Three-Qubit State by Using Cluster States and Bell States

A new application of cluster states is investigated for quantum information splitting (QIS) of an arbitrary three-qubit state. In our scheme, a four-qubit cluster state and a Bell state are shared by a sender (Alice), a controller (Charlie), and areceiver (Bob). Both the sender and controller only need to perform Bell-state measurements (BSMs), the receiver can reconstruct the arbitrary three-qubit state by performing some appropriately unitary transformations on his qubits after he knows the measured results of both the sender and the controller. This QIS scheme is deterministic.     

Quantum Secret Sharing Based on Chinese Remainder Theorem

A novel quantum secret sharing (QSS) scheme is proposed on the basis of Chinese Remainder Theorem (CRT). In the scheme, the classical messages are mapped to secret sequences according to CRT equations, and distributed to different receivers by different dimensional superdense-coding respectively. CRT's secret sharing function,together with high-dimensional superdense-coding, provide convenience, security, and large capability quantum channel forsecret distribution and recovering. Analysis shows the security of the scheme.     

Effects of external electric and magnetic fields on the linear and nonlinear intersubband optical properties of finite semi-parabolic quantum dots

In this work, influences of external electric and magnetic fields on the optical rectification coefficient, the linear and the third-order nonlinear optical absorption coefficients as well as refractive index changes of finite semi-parabolic quantum dots are investigated. In this regard, energy eigenvalues and eigenfunctions of the system are calculated numerically, and optical properties are obtained using the compact density matrix approach. The results show that external electric and magnetic fields have a great influence on these optical quantities.     

量子系统保结构计算新进展

本文主要介绍量子系统保结构计算最新进展情况,分以下几部分内容:哈密顿系统的辛算法、适合于量子系统的哈密顿量显含时间的辛算法、A2B模型分子和双原子分子系统的经典轨迹辛算法计算、双原子分子CO在激光场中的经典轨迹的辛算法计算及其振动和解离、定态Schr dinger方程的辛形式及求解定态Schr dinger方程本征值问题的辛 打靶法、含时Schr dinger方程的保结构算法及其在激光原子物理中的应用、伪分立态模型、强激光与原子相互作用的渐近边界条件、"非齐线性正则方程"的辛算法及其在计算强激光场中一维原子的多光子电离和高次谐波发射中的应用以及Heisenberg方程的保结构计算等等。