Generation of atomic cluster states through the cavity input-output process

We propose a scheme to implement a two-qubit controlled-phase gate for single atomic qubits, which works in principle with nearly ideal success probability and fidelity. Our scheme is based on the cavity input-output process and the single-photon polarization measurement. We show that, even with the practical imperfections such as atomic spontaneous emission, weak atom-cavity coupling, violation of the Lamb-Dicke condition, cavity photon loss, and detection inefficiency, the proposed gate is feasible for generation of a cluster state in that it meets the scalability criterion and it operates in a conclusive manner. We demonstrate a simple and efficient process to generate a cluster state with our high probabilistic entangling gate.     

Excitation of a cavity by a microwave pulse transmitted through a nonreflective cavity compressor

Excitation of a cavity by a phase-modulated pulse transmitted through a chain of nonreflective cavities is considered. It is shown that for a linear frequency-modulated rectangular pulse, the use of a two-cavity compressor increases the energy stored in the cavity fourfold for the same efficiency of its excitation.     

Optical Bell state and Greenberger-Horne-Zeilinger-state analyzers through the cavity input-output process

With the ancillary one-sided cavities each trapping an alkali atom, the schemes for the analyzers of two-photon Bell states and three-photon Greenberger-Horne-Zeilinger (GHZ) states are proposed, respectively. Moreover, all of two-photon Bell states and three-photon GHZ states can be nondestructively distinguished. The influence of atomic spontaneous emission and output coupling inefficiency are discussed.     

Simulation of convective flows in irregular channels on the example of the human nasal cavity and paranasal sinuses

Technical Physics - Here we explore possibilities of the detached eddy simulation models (DES-models) in relation to a human nasal cavity as to a complicated structure of variable section with...     

Preparation of Greenberger-Horne-Zeilinger and W states of three atoms trapped in one cavity through cavity output process

We propose a protocol to generate Greenberger-Horne-Zeilinger (GHZ) and W states of three atoms trapped in only one cavity. The setup involves one cavity and linear optical elements. The quantum information of each qubit is skillfully encoded on the degenerate ground states of the three different atoms, hence the entanglement between them is relatively stable against spontaneous emission. The advantages of the protocol are their robustness against detection inefficiency and asynchronous emission of the photons. We discuss the issue related to the practical implementation and show that the protocol is accessible within the current cavity QED technology and linear optical technology.     

Measure of the tunnelling time of a single photon through a Fabry-Perot cavity

The displacement of the peak of a wavepacket that crosses an empty Fabry-Perot cavity is measured by using photon pairs generated by parametric down conversion, a Hong-Ou-Mandel (HOM) interferometer and coincidence detection. The Fabry-Perot cavity distorts the photon wavepacket. The HOM interferometer is a good tool to map this distortion. We discuss the corrections which must be made in the two-photon inteference results, in order to achieve the true data researched. Even in the absence of active absorbers media or media with inverted atomic populations, superluminal-like effects connected with the tunnelling phenomena are observed. An interpretation of the experimental results in the causality frame is given.     

Nonclassicality generated by propagation of atoms through a cavity field

We successively pass two V-type three-level atoms through a single-mode cavity field. Considering the field to be initially in a classical state, we evaluate various statistical properties such as the quasiprobability Q function, Wigner distribution, Mandel?s Q parameter and normal squeezing of the resulted field. We notice that the sequential crossing of atoms induces nonclassicality into the character of a pure classical state (coherent field). The initial thermal field shows sub-Poissonian as well as squeezing property after interacting with the V atoms.     

Optical bistability through the cavity effect in a four-level open atomic medium

The optical bistability and multistability behavior in a ring cavity for the four-level open atomic system, driven by two coupling fields has been analyzed. It is shown that the presence of exit rate from cavity is having a dominant effect on generating the optical bi(multi) stability on the system. It is found that the effects of the injection rates can be used to control the threshold intensity. It is also found that optical bistability can convert to optical multistability or vice versa via the effect of intensity and detuning of the coupling fields.     

Propagation of polarized photons through a cavity with an anisotropic metamaterial

We present a theoretical study of the propagation properties of polarized photons passing through the cavity with an anisotropic metamaterial. We find that the resonant peaks of transmission appear for photons polarized in a certain direction corresponding to a negative element of the permittivity tensor. This indicates the potential for applying such cavity structures as filters for photons with certain polarizations. The resonant peak of transmission for photons having a given frequency can be achieved by adjusting the thicknesses of the air and metamaterial. If the frequency of the incident photons and the thickness of the metamaterial are fixed, the cavity structure can be used as a photon switch controlled by the thickness of the air. The effect of the absorption is considered, and the result shows that the transmission peak always appears, even for metamaterials with large absorption. Finally, the polarization manipulation of such structures is explored.     

The Evaluation of the Flow of Agents with Isotopic Tracers through Tanks

In this paper the existing methods of evaluating the effectiveness of mixing processes are presented. Starting from the results of experiments based on the use of isotopic technique, a new criterion for the mixing effect of the component flowing through a tank has been found. For this reason, model tests in aerated rooms have been carried out. Properties of the new criterion as well as the relationships to the existing methods of evaluation are given.     

On the Theory of Electric-Current Flow through a Mixture of Charged Particles

Current conduction through a mixture made of two species of positively charged particles is considered where one of the latter species participates in the exchange with the surrounding medium. A solution to the electrodiffusion equations together with Poisson's equation is obtained in the first approximation in terms of the small parameter. A condition is determined where the distribution of charged particles involved in the exchange with the surrounding medium is derived using the diffusion equation for neutral particles. It is shown that the solution to the electrodiffusion equations contains a component decaying with time.     

原子在双腔场间的光子辐射

考虑单个二能级原子穿过两个空间分离的单模腔场,研究原子质心运动的动能、腔长和腔间距对原子的光子辐射率的影响.结果表明,在原子的动能较小时,光子辐射率在双腔系统中出现多共振峰结构并且这种共振峰的数目随腔间距的增大而增加,此时原子在第一个腔中的光子辐射率普遍大于在第二个腔中的;在原子的动能较大时,原子在第一个腔中的光子辐射率与第二个腔中的光子辐射率呈交替变化.该结果说明,可以通过控制原子的速度而对原子的光子辐射率进行调控. 关键词： 光子辐射率 单模腔场 二能级原子     

Theoretical investigation of an electron beam propagating through a wide gap cavity

This paper presents a self-consistent nonlinear theory of the current and energy modulations when an electron beam propagates through an inductively-loaded wide gap cavity. The integro-differential equations axe obtained to describe the modulation of the beam current and kinetic energy. A relativistic klystron amplifier （RKA） model is introduced, which uses an inductively-loaded wide gap cavity as an input cavity. And a numerical code is developed for the extended model based on the equations, from which some relations about the modulated current and modulated energy are numerically given.     

Generation of field cluster states through collective operation of cavity QED disentanglement eraser

We investigate effects of a collective disentanglement eraser performed over states of two pairs of pre-entangled cavities tagged independently with two identical three-level atoms. It is shown that the collective disentanglement operation ensures not only the recovery of initial coherence but also its extension from the initial two to four qubits, generating four-qubit field cluster states. We also propose a cavity QED scheme to generate an arbitrary field graph state by means of a collective operation of disentanglement erasers.     

Current correlations for the transport of interacting electrons through parallel quantum dots in a photon cavity

We calculate the current correlations for the steady-state electron transport through multi-level parallel quantum dots embedded in a short quantum wire, that is placed in a non-perfect photon cavity. We account for the electron–electron Coulomb interaction, and the para- and diamagnetic electron–photon interactions with a stepwise scheme of configuration interactions and truncation of the many-body Fock spaces. In the spectral density of the temporal current–current correlations we identify all the transitions, radiative and non-radiative, active in the system in order to maintain the steady state. We observe strong signs of two types of Rabi oscillations.