Impulsive forces of two spark-generated cavity bubbles with phase differences

The characteristics of synchronous and phase difference bubble pairs in axisymmetric configuration near a boundary are investigated experimentally by the spark discharge method. Their destructive forces on nearby boundaries are measured using a polyvinylidene fluoride sensor. The bubble pair interactions and deformed features in the boundary vicinity are dissimilar to those in bulk water. Moreover, significant discrepancies between in-phase and out-of-phase pair interactions and their intensities of impulses are also witnessed. The interbubble distance (η), stand-off distance from the boundary (γ), and phase offset (τ) are crucial parameters affecting the shape evolutions and impulsive forces. From the qualitative analysis of sensor acquisition and high-speed imaging, it is observed that bubble periods are either prolonged or shorter than their corresponding isolated single cavity according to different parameters and arrangements. Additionally, the strongest impingements are produced by in-phase pairs. The impulses of phase difference bubble pairs are remarkably lower than in-phase pairs and even lower than a single bubble in some arrangements.     

Improvement on the manipulation of a single nitrogen-vacancy spin and microwave photon at single-quantum level

It remains a great challenge to realize direct manipulation of a nitrogen-vacancy(NV) spin at the single-quantum level with a microwave(MW) cavity. As an alternative, a hybrid system with the spin–phonon–photon triple interactions mediated by a squeezed cantilever-type harmonic resonator is proposed. According to the general mechanical parametric amplification of this in-between phonon mode, the direct spin–phonon and photon–phonon couplings are both exponentially enhanced, which can even further improve the coherent manipulation of a single NV spin and MW photon with a higher efficiency. In view of this triple system with enhanced couplings and the additional sideband adjustable designs, this scheme may provide a more efficient phonon-mediated platform to bridge or manipulate the MW quantum and a single electron spin coherently. It is also hoped to evoke wider applications in the areas of quantum state transfer and preparation,ultrasensitive detection and quantum nondestructive measurement, etc.     

Preparation of two and four atom entangled states

A scheme for preparing two and four atom entangled states is presented. It is based on atom cavity field interactions. Firatly, the cavity is prepared in the superposition of the number states through the atom undergoing a two photon transition, the secondly, the two or four identical two level atoms, which are all initially in their ground states, are sent through the cavity sequentially and can make resonant single photon transition in the cavity. Then atomic entangled states are created and the cav     

Investigation of soliton pairs in an erbium-doped fiber laser with large normal dispersion

We experimentally investigate the soliton pairs in a passively mode-locked erbium-doped fiber laser with large normal cavity dispersion. By adjusting the polarization state, four different kinds of soliton pairs are achieved. The pulses in soliton pairs exhibit different temporal separations, and show randomly distributed spikes on the top-flat of spectra. The pulse-pulse interactions in the soliton pairs are investigated, and it is suggested that the pulse separation, pulse duration, and their relative intensities all determine the strength of pulse interactions.     

Plasmon-mediated interaction between physically adsorbed atoms — curvature effect

The quantum-mechanical formulation of the non-retarded interaction of a single atom with a metallic surface is extended to the study of two neighboring atoms in the presence of a metallic surface. The atoms are represented as fluctuating three-dimensional oscillators, whereas the metal gives a dynamical response through the interaction of the surface plasma oscillations with the external fluctuating dipole. In the total energy balance, one finds, besides the two-body atom-atom and atom-surface interactions, a three-body contribution arising from the surface mediated atom-atom interaction. The flat-surface case is first treated to illustrate how this plasmon-mediated interaction takes place. Then for the general case of two atoms in presence of a curved surface, the three-body interaction term is evaluated. Application is made to the case of a surface having the shape of a spherical particle or a spherical cavity. Numerical evaluation for the case of two argon atoms on solid aluminium has been made in order to determine the relative importance of the modified lateral interaction and the dependence on the radius for the particle or the cavity configuration.     

Entanglement purification of gaussian continuous variable quantum states

We describe an entanglement purification protocol to generate maximally entangled states with high efficiencies from two-mode squeezed states or from mixed Gaussian continuous entangled states. The protocol relies on a local quantum nondemolition measurement of the total excitation number of several continuous variable entangled pairs. We propose an optical scheme to do this kind of measurement using cavity enhanced cross-Kerr interactions.     

On the thermodynamic behaviors and interactions between bubble pairs: A numerical approach

Thermodynamic behaviors and interactions between bubble pairs are important to better understand the cavitation phenomena. In this study, a compressible two-phase model, accounting for thermal effects to investigate the thermodynamic behaviors and interactions between bubble pairs, is developed in OpenFOAM. The volume of fluid (VOF) method is adopted to capture the interface. Validations are performed by comparing the simulation results of a single bubble and bubble pairs with corresponding experimental data. The dynamical behaviors of bubble pairs and their thermodynamic effect at different relative distances γ are investigated and discussed, which help reveal the bubble cloud dynamics. The quantitative analysis of γ effects on the maximum temperature during bubble collapse is performed with three distinct stages identified. For a single bubble collapsing near the rigid surface, the thermodynamic characteristics at different relative distances are similar to that of the bubble pairs, but the maximum temperature is higher since the single bubble can collapse to a smaller volume.     

Scheme for Realizing Deterministic Entanglement Concentration with Atoms Via Cavity QED

A scheme for concentrating entanglement in two partially entangled Einstein-Podolsky-Rosen (EPR) pairs using repetitious resonant interactions of the atoms with a single-mode cavity field is proposed. A maximally entangled EPR pair can be deterministically extracted with the success probability of 1.0. In the scheme, the two logical states of a qubit are represented by the two lowest levels of an atom while a higher-energy intermediate level is used to facilitate the realization of the unitary operations, and all the operations required to realize deterministic entanglement concentration can be implemented in a reasonable amount of time before decoherence sets in. The scheme might be experimentally realizable with presently available cavity QED techniques and gives a realistic means to realize entanglement concentration deterministically.     

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.     

Quantum dynamics of atomic magnets: cotunneling and dipolar-biased tunneling

Multispin tunneling cross relaxations in an ensemble of weakly coupled Ho3+ ions, mediated by weak anisotropic dipolar interactions, can be evidenced by ac-susceptibility measurements in a high temperature regime. Based on a four-body representation, including the rare-earth nuclear spin, two-ion tunneling mechanisms can be attributed to both dipolar-biased tunneling and cotunneling processes. The coreversal involving entangled pairs of magnetic moments is discussed with a particular emphasis, giving new evidence to elucidate the many-body quantum dynamics in dipolar spin glasses.     

Bound soliton pulses in passively mode-locked fiber laser

A passively mode-locked soliton fiber ring laser was successfully demonstrated, and bound soliton pulses with an FWHM pulsewidth of 326 fs and fixed separation of 938 fs were first observed. The number of bound soliton pairs in the cavity can be controlled under lower pump power. The transmission effects were investigated by injecting bound soliton pulses into a single mode fiber.     

Environment induced entanglement in cavity-QED

The effects of dissipative dynamics on the magnitude of entanglement generated In atom-photon interactions inside cavities is studied. We present some concrete examples of environment Induced entanglement in alom-photon interactions. We consider various dissipative atom-cavity systems and show that their collective dynamics can be used to maximize entanglement for intermediate values of the cavity leakage parameter κ. We first consider the interaction of a single two-level atom with one of two coupled microwave cavities and show analytically that the atom-cavity entanglement increases with cavity leakage. We next consider a system of two atoms passing successively through a cavity and derive the expression for the maximum value of in terms of the Rabi angle gt, for which the two-atom entanglement can be Increased. Finally, numerical investigation of micromaser dynamics also reveals the increase of two-atom entanglement with stronger cavity-environment coupling for experimentally attainable values of the micromaser parameters.     

Mutual preservation of entanglement

We study a generalized double Jaynes–Cummings (JC) model where two entangled pairs of two-level atoms interact indirectly. We show that there exist initial states of the qubit system so that two entangled pairs are available at all times. In particular, the minimum entanglement in the pairs as a function of the initial state is studied. Finally, we extend our findings to a model consisting of multi-mode atom–cavity interactions. We use a non-Markovian quantum state diffusion (QSD) equation to obtain the steady-state density matrix for the qubits. We show that the multi-mode model also displays dynamical preservation of entanglement.     

Tests of quantum mechanics with single atoms in high Q cavities

A Rydberg atom coupled to a single field mode in a high Q superconducting cavity is an ideal tool to perform experiments testing the most puzzling aspects of the quantum theory. The coupling between the atom and the field is either resonant or dispersive. In the resonant case, quantum Rabi oscillations in the vacuum or in a small coherent field injected in the cavity are observed. The analysis of these signals reveals in a striking way the quantization of the field. Quantum Rabi oscillations are also used to produce entanglement between successive atoms crossing the cavity. Dispersive atom-field coupling is used to prepare coherent superpositions of field states with different phases (Schrödinger cat states). The progressive decoherence of these states is studied by measuring correlations between the energies of pairs of atoms sent through the cavity with a variable delay between them. These experiments provide fundamental tests of quantum theory and shed light on the transition from quantum to classical in mesoscopic systems.     

Unusual directional dependence of exchange energies in GaAs diluted with Mn: is the RKKY description relevant?

Ferromagnetism in Mn-doped GaAs, the prototypical dilute magnetic semiconductor (DMS), has so far been attributed to hole mediated RKKY-type interactions. First-principles calculations reveal a strong direction dependence of the ferromagnetic (FM) stabilization energy for Mn pairs, a dependence that cannot be explained within RKKY. In the limit of a hostlike hole engineered here where the RKKY model is applicable, the exchange energies are strongly reduced, suggesting that this limit cannot explain the observed ferromagnetism. The dominant contribution stabilizing the FM state is found to be maximal for 110-oriented Mn pairs and minimal for 100-oriented Mn pairs, providing an alternate explanation for magnetism in such materials in terms of energy lowering due to p-d hopping interactions, and offering a new design degree of freedom to enhance FM.     

双电极对双脉冲激光器结构分析

本文对双电极对双脉冲激光器的谐振腔结构进行了分析,结果表明采用双非稳腔和增大反射镜的曲率半径可分别获得单纵模和基横模输出。为使输出能量稳定,则双电极对的间距有一最小值的限制。     

Vibrating soliton pairs in a mode-locked laser cavity

We show numerically the existence of vibrating soliton pairs that are consistent with observations performed with a passively mode-locked fiber laser. These vibrating pairs are new types of multisoliton complexes that exist in the vicinity of the phase-locked soliton pairs discovered a few years ago [Opt. Lett.27, 966 (2002)]. The pairs are found numerically with a laser propagation model that includes nonlinear dissipation and cavity periodicity, and they can appear following a Hopf-type bifurcation when a cavity parameter is tuned.     

Dynamical coupling between a Bose–Einstein condensate and a cavity optical lattice

A Bose–Einstein condensate is dispersively coupled to a single mode of an ultra-high finesse optical cavity. The system is governed by strong interactions between the atomic motion and the light field even at the level of single quanta. While coherently pumping the cavity mode the condensate is subject to the cavity optical lattice potential whose depth depends nonlinearly on the atomic density distribution. We observe optical bistability already below the single photon level and strong back-action dynamics which tunes the coupled system periodically out of resonance.     

双共焦波导结构二次谐波太赫兹回旋管谐振腔设计

准光共焦波导具有功率容量大、模式密度低的特点,能够有效地减少模式竞争对回旋管互作用的影响,有利于高次谐波太赫兹回旋管的设计.为提高太赫兹准光回旋管的互作用效率,在共焦柱面波导的基础上,研究了一种新型高频互作用结构——双共焦波导结构,设计了一种330 GHz二次谐波双共焦结构回旋管谐振腔并对其进行了理论分析和粒子模拟.研究结果表明,双共焦谐振腔中的高阶模式能够与高次电子回旋谐波发生稳定的相互作用,并且没有模式竞争现象,具备工作在太赫兹波段的潜力.相比普通共焦波导谐振腔,双共焦谐振腔能够增强准光回旋管的注波互作用强度,提高回旋管的输出功率和工作效率.此外,结果还表明双共焦波导中的电磁波模式是一种由两个独立的共焦波导模式叠加而成的混合模式.利用这种混合模式有望实现太赫兹回旋管的单注双频工作,为新型太赫兹辐射源的研究提供了新的途径.     

Continuous-wave, totally fiber integrated optical parametric oscillator using holey fiber

We present, for the first time to our knowledge, a cw, all-fiber optical parametric oscillator that uses a holey fiber. The oscillator operates at 1.55 microns and can yield an oscillating parametric signal that consists of a single line with a 30-dB extinction ratio and a 10-pm linewidth or that consists of multiple lines. In addition to the signal and the idler, five other pairs of spectral lines can be observed that are due to multiple parametric interactions. The source reaches threshold for a pump power of 1.28 W and saturates for pump powers in excess of approximately 1.6 W.