Collective atomic motion in an optical lattice formed inside a high finesse cavity

We report on collective nonlinear dynamics in an optical lattice formed inside a high finesse ring cavity in a so far unexplored regime, where the light shift per photon times the number of trapped atoms exceeds the cavity resonance linewidth. We observe bistability and self-induced squeezing oscillations resulting from the retroaction of the atoms upon the optical potential wells. We can well understand most of our observations within a simplified model assuming adiabaticity of the atomic motion. Nonadiabatic aspects of the atomic motion are reproduced by solving the complete system of coupled nonlinear equations of motion.     

Velocity field vortices and Mermin-Ho vortices in two-component spinor BEC

In light of the φ-mapping topological current theory, two important vortex structures in two-component spinor BEC—the velocity field vortices and the Mermin-Ho vortices are discussed. It is revealed that these two different kinds of vortices are created respectively from the zero points of two different order parameter configurations in the condensates, and both their topological charges, locations and motions can be determined by the φ-mapping theory.     

High temperature BEC with photon-like atomic polaritons

We consider the problem of high temperature (room and beyond) true Bose-Einstein condensation (BEC) of trapped ideal 1D gas of low branch (LB) atomic polaritons for the system of two-level atomic ensemble interacting with a quantized single-mode electromagnetic field in the presence of optical collisions (OC) with buffer gas atoms. We discuss the application of biconical waveguide cavity (BWC) for observing predicted effects.     

Buongiorno's model nanofluid natural convection inside a square cavity with thermal radiation

Natural convection flow and heat transfer characteristics of Buongiorno's mathematical model nanofluid flow inside square cavity with isothermal conditions on both side walls and adiabatic conditions on top and bottom walls is studied numerically in this analysis. Finite difference method is employed to solve the governing partial differential equations formulated in stream function, nanoparticle volume fraction and temperature numerically. The results are presented in the form of streamlines, isotherms, isoconcentrations, local Nusselt number and Sherwood number for various values of influenced parameters, such as, Rayleigh number (100 ≤ Ra ≤ 300), buoyancy ratio parameter (0.1 ≤ Nr ≤ 0.9), Lewis number (1.0 ≤ Le ≤ 10), thermophoresis number (0.1 ≤ Nt ≤ 0.5), Brownian motion number (0.1 ≤ Nb ≤ 0.9) and radiation number (0.1 ≤ R ≤ 0.9) and are represented through graphs. It is detected that the values of rate of heat transfer elevates with rising values of Rayleigh number (Ra).     

Preparation of optimal entropy squeezing state of atomic qubit inside the cavity via two-photon process and manipulation of atomic qubit outside the cavity

Considering two atomic qubits initially in Bell states, we send one qubit into a vacuum cavity with two-photon resonance and leave the other one outside. Using quantum information entropy squeezing theory, the time evolutions of the entropy squeezing factor of the atomic qubit inside the cavity are discussed for two cases, i.e., before and after rotation and measurement of the atomic qubit outside the cavity. It is shown that the atomic qubit inside the cavity has no entropy squeezing phenomenon and is always in a decoherent state before the operating atomic qubit outside the cavity. However,the periodical entropy squeezing phenomenon emerges and the optimal entropy squeezing state can be prepared for the atomic qubit inside the cavity by adjusting the rotation angle, choosing the interaction time between the atomic qubit and the cavity, controlling the probability amplitudes of subsystem states. Its physical essence is cutting the entanglement between the atomic qubit and its environment, causing the atomic qubit inside the cavity to change from the initial decoherent state into maximum coherent superposition state, which is a possible way of recovering the coherence of a single atomic qubit in the noise environment.     

A simple model for maser action obtained through a magnetic tunnel junction placed inside a resonant cavity

Magnetic tunnel junctions are currently being used in magnetoresistive reading heads, magnetic field sensors and MRAMs, due to its giant magnetoresistance effect whose roots are linked to strong spin-dependent scattering mechanisms. The existence of spin-polarized currents in such devices posed us the question over the possibility to generate coherent microwave radiation in a spin inverted population medium, maintained through a spin-polarized current. In this paper we investigate the possibility of obtaining a maser effect considering a magnetic tunnel junction placed inside a resonant cavity. We put forward a simple model based on phenomenological rate equations, being the spin-polarized currents determined by the physics of the magnetic tunnel junction.     

Time-of-flight flow imaging of two-component flow inside a microfluidic chip

Here we report on using NMR imaging and spectroscopy in conjunction with time-of-flight tracking to noninvasively tag and monitor nuclear spins as they flow through the channels of a microfluidic chip. Any species with resolvable chemical-shift signatures can be separately monitored in a single experiment, irrespective of the optical properties of the fluids, thereby eliminating the need for foreign tracers. This is demonstrated on a chip with a mixing geometry in which two fluids converge from separate channels, and is generally applicable to any microfluidic device through which fluid flows within the nuclear spin-lattice relaxation time.     

Quantum Fisher information for a qubit system placed inside a dissipative cavity

We study the time evolution of the quantum Fisher information of a system whose the dynamics is described by the phase-damped model. We discuss the correlation between the Fisher information and entanglement dynamics of a qubit and single-mode quantized field in a coherent state inside phase-damped cavity. Analytic results under certain parametric conditions are obtained, by means of which we analyze the influence of dissipation on the negativity and quantum Fisher information for different values of the estimator parameter. An interesting monotonic relation between the Fisher information and nonlocal correlation behavior is observed during the time evolution.     

Broadband resonant cavity inside a two-dimensional sonic crystal

A rectangular cavity inside a two-dimensional sonic crystal was theoretically and experimentally characterized by examining its response to a cylindrical source emitting narrow-band filtered noise bursts with central frequencies ranging from 2 to 12 kHz. A broadband intensity resonance was observed for frequencies within the full band-gap region of the sonic crystal (5.5–6.5 kHz). Unlike ordinary resonances, this broadband resonance depends on the reflection properties of the sonic crystal forming the surrounding walls rather than on the geometry of the cavity.     

Nonlinear dissipative dynamics of a two-component atomic condensate coupling with a continuum

We investigate the nonlinear dissipative coherence bifurcation and population dynamics of a two-component atomic Bose-Einstein condensate coupling with a continuum. The coupling between the two-component condensates and the continuum brings effective dissipations to the two-component condensates. The steady states and the coherence bifurcation depend on both dissipation and the nonlinear interaction between condensed atoms. The coherence among condensed atoms may be even enhanced by the effective dissipations. The combination of dissipation and nonlinearity allows one to control the switching between different self-trapped states or the switching between a self-trapped state and a non-self-trapped state.     

Quantum computation with quantum-dot spin qubits inside a cavity

Universal set of quantum gates are realized from quantum-dot spin qubits inside a cavity via two-channel Raman interactions. Individual addressing and effective switch of the cavity mediated interaction are directly possible here. This simple realization of all wanted interaction for selective qubits makes current scenario more suitable for scalable quantum computation.     

Prong cross-sections from a realistic two-component model

The inclusive pp → pX data, supporting a large triple Pomeron contribution, is invoked to predict the diffractive multiplicity distributions. Poisson decay is assumed for the excited cluster. The predicted diffractive prong cross-sections agree with the empirical estimates at 200 $\text{GeV}\text{c}$ and suggest a significant broadening at 1500 $\text{GeV}\text{c}$ (giving a rise in σ_T ～ 2.5 mb). Consequently the full prong distribution should develop no dip.     

Forward-backward multiplicity distribution in a two-component model

We calculate stochastic quantities in a two-component model which is a product of a negative binomial and a Poisson distribution. The generating function and the KNO scaling function are obtained. A formula for the forward-backward (F-B) multiplicity correlation is derived from the generating function. We consider the case in which particles are produced in pairs and compare with experiment.     

Correlation and entanglement of a three-level atom inside a dissipative cavity

We discuss the correlation and entanglement of a three-level atom with a single-mode quantized field in a coherent state inside a phase-damped cavity. We analyze the influence of dissipation on the quantum and classical entropy. It has been shown that the quantum, classical and nonextensive entropy are sensitive to any change in the initial state setting of the atom and the quantized field. The relation between the long lived entanglement and dissipation is observed. On the other hand, a short disentanglement can be generated through special values of the atomic motion parameter.     

基于腔QED技术的原子态纠缠纯化方案

基于两能级原子与单模腔场之间的失谐相互作用,我们提出了一个有效的且能够纯化任意未知原子纠缠态的纠缠纯化方案。将量子逻辑门(Phys.Rev.Lett.74,4087(1995))和纠缠纯化(Phys.Rev.Lett.76,722(1996))的理论研究的最新进展相结合提出了一个在实验上可行的纠缠纯化物理方案。     

Entropy of a two-component fluid in a square-well model

An analytical expression valid for two approximations, notably, the random phase approximation (RPA) and the mean spherical approximation (MSA), is derived for entropy of a two-component system with the pair potential of a square well (SW). This expression is applied to calculate the excess entropy of mixing of the Na-K and Na-Cs equiatomic compositions. It is shown that the use of the SW model leads to better results than the application of the hard-sphere model. The MSA gives better convergence with the experiment compared with the RPA.     

A simplified finite element method for studying acoustic characteristics inside a car cavity

A simplified finite element method has been developed for analyzing the acoustic resonances of a prismatic car cavity. Use is made of the non-variant geometric and material properties of such a cavity in one direction (across the width of the car) and the solution of the full three-dimensional problem is related very simply to the solution of a single two-dimensional problem, with a consequent reduction of computing effort. Some experimental results obtained for a half-size model of a car cavity are compared with the finite element results. The accuracy of the finite element solution is assessed by analyzing a rectangular cavity and a cylindrical cavity, for which analytical solutions are already available.     

Scalable quantum computing with Josephson charge-phase qubits inside a cavity

This Letter proposes a theoretical scheme for scalable quantum computing with charge-phase qubits inside a common cavity. Individually addressing the applied gate pulses, we obtain the switchable interqubit couplings mediated by the cavity mode, from which a universal set of logic gates can be constructed. In our scheme the interqubit couplings are completely feasible to perform conditional gates, and the classical microwaves cause negligible leakage errors.     

在腔耦合的超导量子比特中实现几何量子信息处理

用量子空腔耦合的超导电荷比特器件被认为是实现量子信息处理的相当有希望的体系之一.如何在这种可集成的量子体系中实现高保真度的操作是量子信息处理领域的重要课题.文章介绍作者最近提出的在量子腔耦合的超导量子比特中用具有内禀容错功能的几何操作来实现普适量子逻辑门,产生多比特量子纠缠及实现量子纠错编码的一个可行方案.