Complementarity via Minimum Error Measurement in a Two-Path Interferometer

We study the fringe visibility and the which-path information(WPI) of a general Mach-Zehnder interferometer with an asymmetric beam splitter(BS). A minimum error measurement in the detector is used to extract the WPI. Both the fringe visibility V and the WPI I_(path) are affected by the initial state of the photon and the second asymmetric BS. The condition in which the WPI takes the maximum is obtained. The complementarity relationship V~2 + I_(path)~2 ≤ 1 is found, and the conditions for equality are also presented.     

A certain critical two-soliton solution of the nonlinear Schroedinger equation

An exact two-soliton solution of the nonlinear Schroedinger equation is derived by using the Hirota direct approach. This solution describes such a critical process that two still solitons separated infinitely approach and then pass through each other and keep straight on infinitely.     

Linear optical implementation of optimal unambiguous discrimination among quantum states

In this paper, we present a linear optical scheme for optimal unambiguous discrimination among nonorthogonal quantum states in terms of the multiple-rail and polarization representation of a single photon. In our scheme, discriminated quantum states are expressed by using the spatial degree of freedom of a single photon while the polarization degree of freedom of the single photon is used to act as an auxiliary qubit. The optical components used in our scheme are only passive linear optical elements such as polarizing beam splitters, wave plates, polarizers, single photon detectors, and single photon source.     

Fringe visibility for two qubits interacting with a macroscopic medium

We study both the two-particle and single-particle fringe visibility in the generalized version of the Nakazato–Pascazio model where two qubits interact with a finite length one-dimensional array.Both the two-particle and single-particle fringe visibilities are investigated with different initial states of the particles spin.For different initial states of the particles spin,the two-particle fringe visibility either decreases or increases over time,and may even decrease first and increase later.Due to the interaction between the particles and the one-dimensional array,the single-particle fringe visibility increases over time when the initial state of the two particles spin is independent.The single-particle fringe visibility is equal to 0 as the two-particle spin is initially in the completely entangled state or in the singlet state.     

Spatial Dependent Spontaneous Emission of an Atom in a Semi-Infinite Waveguide of Rectangular Cross Section

We study a quantum electrodynamics(QED) system made of a two-level atom and a semi-infinite rectangular waveguide, which behaves as a perfect mirror in one end. The spatial dependence of the atomic spontaneous emission has been included in the coupling strength relevant to the eigenmodes of the waveguide. The role of retardation is studied for the atomic transition frequency far away from the cutoff frequencies. The atom-mirror distance introduces different phases and retardation times into the dynamics of the atom interacting resonantly with the corresponding transverse modes. It is found that the upper state population decreases from its initial as long as the atom-mirror distance does not vanish, and is lowered and lowered when more and more transverse modes are resonant with the atom. The atomic spontaneous emission can be either suppressed or enhanced by adjusting the atomic location for short retardation time.There are partial revivals and collapses due to the photon reabsorbed and re-emitted by the atom for long retardation time.     

非线性偏微分方程的多孤子解

对齐次平衡法的一些关键步骤进行拓宽,获得了一系列非线性方程的多孤子解,使得对非线性方程的多孤子解的求解方法更加直接,且许多步骤可以利用计算机完成. 关键词： 齐次平衡法 非线性方程 多孤子解     

Quantum routing of few photons using a nonlinear cavity coupled to two chiral waveguides

We investigate few-photon scattering properties in two one-dimensional waveguides chirally coupled to a nonlinear cavity. The quantum states of scattered few photons are solved analytically via a real-space approach, and the solution indicates the few-photon reflection and transmission properties. When inputting two photons of equal energy to resonate with the cavity, the propagation characteristics of the two photons will be interesting, which is different from the previous anti-bunching effects with a quantum emitter. More importantly, when the total energy of the two incident photons equals the energy of a nonlinear cavity accommodating two photons, influence of the bound state will become larger to result in disappearance of antibunching effect. However, the bound state has no effect on probability of routing to another waveguide.     

Bose—Einstein Condensation in a Spherical Symmetric Harmonic Trap

Using a perturbation theory approach,we derive an approximate analytical solution of the Gross-Pitaevskii equation in a spherical symmetric harmonic trap.This solution is consistent with that obtained numerically.