Optical gap solitons: Past,present, and future; theory and experiments

Optical gap solitons refer to nonlinear waves propagating in optical fibers whose linear refractive index has a periodic variation. Stationary gap solitons came to light first in 1987 [Chen and Mills, Phys. Rev. Lett. 58, 160 (1987)]; two years later, they re-emerge in Christodoulides and Joseph [Phys. Rev. Lett. 62, 1746 (1989)] and are first extended to a more general traveling wave form in Aceves and Wabnitz [Phys. Lett. A 141, 37 (1989)]. But it was not until seven years later, that the first experimental demonstration [Eggleton et al., Phys. Rev. Lett. 76, 1627 (1996); J. Opt. Soc. Am. B 14, 2980 (1997)] was reported. Since then, there has been an increase in the study of the dynamics and applications of such solitons. This paper is a brief survey of some of the ongoing and future research on optical gap solitons. (c) 2000 American Institute of Physics.     

Tkachenko modes of vortex lattices in rapidly rotating bose-einstein condensates

We calculate the in-plane modes of the vortex lattice in a rotating Bose condensate, from the slowly rotating to mean-field quantum Hall limits. The Tkachenko mode frequency, linear in wave vector k for lattice rotational velocities Omega much smaller than the lowest sound wave frequency in a finite system, becomes quadratic in k in the opposite limit. The system also supports an inertial mode of frequency >or=2omega. The calculated frequencies are in excellent agreement with recent observations of Tkachenko modes by Phys. Rev. Lett., 91, 100402 (2003)].     

Asymmetric, helical, and mirror-symmetric traveling waves in pipe flow

New families of three-dimensional nonlinear traveling waves are discovered in pipe flow. In contrast with known waves [H. Faisst and B. Eckhardt, Phys. Rev. Lett. 91, 224502 (2003); H. Wedin and R. R. Kerswell, J. Fluid Mech. 508, 333 (2004), they possess no discrete rotational symmetry and exist at a significantly lower Reynolds numbers (Re). First to appear is a mirror-symmetric traveling wave which is born in a saddle node bifurcation at Re=773. As Re increases, "asymmetric" modes arise through a symmetry-breaking bifurcation. These look to be a minimal coherent unit consisting of one slow streak sandwiched between two fast streaks located preferentially to one side of the pipe. Helical and nonhelical rotating waves are also found, emphasizing the richness of phase space even at these very low Reynolds numbers.     

Bloch-like oscillations in a one-dimensional lattice with long-range correlated disorder

We study the dynamics of an electron subjected to a uniform electric field within a tight-binding model with long-range-correlated diagonal disorder. The random distribution of site energies is assumed to have a power spectrum S(k) approximately 1/k(alpha) with alpha>0. de Moura and Lyra [Phys. Rev. Lett. 81, 3735 (1998)]] predicted that this model supports a phase of delocalized states at the band center, separated from localized states by two mobility edges, provided alpha>2. We find clear signatures of Bloch-like oscillations of an initial Gaussian wave packet between the two mobility edges and determine the bandwidth of extended states, in perfect agreement with the zero-field prediction.     

Exact Entanglement Dynamics in Three Interacting Qubits

Motivated by recent experimental studies on coherent dynamics transfer in three interacting atoms or electron spins [Phys. Rev. Lett 114(2015) 113002, Phys. Rev. Lett 120(2018) 243604], here we study entanglement entropy transfer in three interacting qubits. We analytically calculate time evolutions of wave function, density matrix and entanglement of the system. We find that initially entangled two qubits may alternatively transfer their entanglement entropy to other two qubit pairs. Thus dynamical evolution of three interacting qubits may produce a genuine three-partite entangled state through entanglement entropy transfers. In particular, different pairwise interactions of the three qubits endow symmetric and asymmetric evolutions of the entanglement transfer,characterized by the quantum mutual information and concurrence. Finally, we discuss an experimental proposal of three Rydberg atoms for testing the entanglement dynamics transfer of this kind.     

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。     

Phase-field crystals with elastic interactions

We report on a novel extension of the recently introduced phase-field crystal (PFC) method [Elder, Phys. Rev. Lett. 88, 245701 (2002)10.1103/PhysRevLett.88.245701], which incorporates elastic interactions as well as crystal plasticity and diffusive dynamics. In our model, elastic interactions are mediated through wave modes that propagate on time scales many orders of magnitude slower than atomic vibrations but still much faster than diffusive time scales. This allows us to preserve the quintessential advantage of the PFC model: the ability to simulate atomic-scale interactions and dynamics on time scales many orders of magnitude longer than characteristic vibrational time scales. We demonstrate the two different modes of propagation in our model and show that simulations of grain growth and elastoplastic deformation are consistent with the microstructural properties of nanocrystals.     

Simplified models for vibrational energy transfer in proteins

We consider the transfer of vibrational energy in proteins and derive a simplified model for the resonant energy exchange between different vibrational modes. We use the parameters of an earlier study [K. Moritsugu, et al., Phys. Rev. Lett. 85 (2000) 3970 ] to compare our predictions with the results of the molecular dynamics simulations, and reveal an excellent agreement.     

Hawking radiation and near horizon universality of chiral Virasoro algebra

We show that the diffeomorphism anomaly together with the trace anomaly reveal a chiral Virasoro algebra near the event horizon of a black hole. This algebra is the same irrespective of whether the anomaly is covariant or consistent, thereby manifesting its universal character and the fact that only the outgoing modes are relevant near the horizon. Our analysis therefore clarifies the role of the trace anomaly in the diffeomorphism anomaly approach [Robinson and Wilczek in Phys. Rev. Lett. 95:011303, 2005; Iso et al. in Phys. Rev. Lett. 96:151302, 2006; Banerjee and Kulkarni in Phys. Rev. D 77:024018, 2008; Gangopadhyay and Kulkarni in Phys. Rev. D 77:024038, 2008] to the Hawking radiation.     

Dynamics of geometric discord and measurement-induced nonlocality at finite temperature

By using geometric measure of discord (GMOD) [B. Dakić, V. Vedral, Č. Brukner, Phys. Rev. Lett. 105, 109502 (2010)] and measurement-induced nonlocality (MIN) [S. Luo, S. Fu, Phys. Rev. Lett. 106, 120401 (2011)], we investigate quantum correlation of a pair of two-level systems, each of which is interacting with a reservoir at finite temperature T. We show that, for a broad class of states of the system, GMOD and MIN can endure sudden death, and there is no asymptotic decay for MIN while asymptotic decay exists for GMOD. We also give the dynamics of GMOD and MIN with respect to the temperature and illustrate their different characteristics.     

Experimental observation of high-order quantum accelerator modes

Using a freely falling cloud of cold cesium atoms periodically kicked by pulses from a vertical standing wave of laser light, we present the first experimental observation of high-order quantum accelerator modes. This confirms the recent prediction by Fishman, Guarneri, and Rebuzzini [Phys. Rev. Lett. 89, 084101 (2002)]]. We also show how these accelerator modes can be identified with the stable regions of phase space in a classical-like chaotic system, despite their intrinsically quantum origin.     

Experimental identification of electromagnetically induced transparency in magnetized plasma

We report the first experimental identification of the new wave branch at electron cyclotron frequency produced by the injection of a frequency-matched intense pump wave in magnetized plasma [A.?G. Litvak and M.?D. Tokman, Phys. Rev. Lett. 88, 095003 (2002); G. Shvets and J.?S. Wurtele, Phys. Rev. Lett. 89, 115003 (2002)], which is a classical phenomenon analogous to electromagnetically induced transparency (EIT) in quantum systems. By using a frequency-sweep interferometer, we directly detected the dispersion relation of the plasma EIT branch for propagation parallel to the background magnetic field. The bandwidth of the EIT window was correlated with the pump-wave electric field and was found to agree with the theoretical prediction.     

Collective modes and ballistic expansion of a fermi gas in the BCS-BEC crossover

We evaluate the frequencies of collective modes and the anisotropic expansion rate of a harmonically trapped Fermi superfluid at varying coupling strengths across a Feshbach resonance driving a BCS-BEC crossover. The equations of motion for the superfluid are obtained from a microscopic mean-field expression for the compressibility and are solved within a scaling ansatz. Our results confirm nonmonotonic behavior in the crossover region and are in quantitative agreement with current measurements of the transverse breathing mode by Kinast et al. [Phys. Rev. Lett. 92, 150402 (2004)]] and of the axial breathing mode by Bartenstein et al. [Phys. Rev. Lett. 92, 203201 (2004)]].     

Continuous variable entanglement using cold atoms

We present an experimental demonstration of both quadrature and polarization entanglement generated via the interaction between a coherent linearly polarized field and cold atoms in a high finesse optical cavity. The nonlinear atom-field interaction produces two squeezed modes with orthogonal polarizations which are used to generate a pair of nonseparable beams, the entanglement of which is demonstrated by checking the inseparability criterion for continuous variables recently derived by Duan et al. [Phys. Rev. Lett. 84, 2722 (2000)]] and calculating the entanglement of formation [Phys. Rev. Lett. 91, 107901 (2003)]].     

Periodic entanglement of magnons in an antiferromagnet

The dynamics of entanglement for two-mode magnons in an antiferromagnet is investigated according to the entanglement criterion proposed by Duan et al. [L.M. Duan, G. Giedke, J.I. Cirac, P. Zoller, Phys. Rev. Lett. 84 (2000) 2722]. It is shown that entanglement between the two modes of magnons can be generated and occurs periodically with time.     

Destabilization of fast-ion-induced long sawteeth by localized current drive in the JET tokamak

In a tokamak fusion reactor the energetic alpha particles will transiently stabilize the magnetohydrodynamic activity causing sawtooth oscillations. The crash events terminating long sawtooth free periods can provide seed islands for neoclassical tearing modes [Phys. Rev. Lett. 88, 105001 (2002)]]. To shorten the sawtooth periods localized current drive near the q=1 surface is a possibility. This Letter provides the first experimental evidence for the effectiveness of this method in the different physics regime associated with fast-ion-induced long sawteeth on the JET tokamak.     

Beliaev damping and Kelvin mode spectroscopy of a Bose-Einstein condensate in the presence of a vortex line

It is demonstrated theoretically that the counter-rotating quadrupole mode in a vortex of Bose-Einstein condensates can decay into a pair of Kelvin modes via the Beliaev process. We calculate the spectral weight of a density-response function within the Bogoliubov framework, taking account of both Beliaev and Landau processes. Good agreement with experiment on 87 Rb by Bretin et al. [Phys. Rev. Lett., 100403 (2003)]] allows us to unambiguously identify the decayed mode as the Kelvin wave propagating along a vortex line.     

Collective excitations of a trapped Bose-Einstein condensate in the presence of a 1D optical lattice

We study low-lying collective modes of an elongated 87Rb condensate produced in a 3D magnetic harmonic trap with the addition of a 1D periodic potential which is provided by a laser standing wave along the axial direction. While the transverse breathing mode remains unperturbed, quadrupole and dipole oscillations along the optical lattice are strongly modified. Precise measurements of the collective mode frequencies at different heights of the optical barriers provide a stringent test of the theoretical model recently introduced [M. Kr?mer, Phys. Rev. Lett. 88, 180404 (2002)]].     

Non-Abelian states with negative flux: a new series of quantum Hall states

By applying the idea of parafermionic clustering to composite bosons with positive as well as negative flux, a new series of trial wave functions to describe fractional quantum Hall states is proposed. These states compete at filling factors nu=k/(3k+/-2) with other ground states like stripes or composite-fermion states. These series contain all the states recently discovered by Pan et al. [Phys. Rev. Lett. 90, 016801 (2003)10.1103/Phys. Rev. Lett. 90, 016801(2003)] including the even-denominator cases. Exact diagonalization studies on the sphere and torus point to their relevance for nu=3/7, 3/11, and 3/8.     

Are avalanches in sandpiles a chaotic phenomenon?

We show that deterministic systems with strong nonlinearities seem to be more appropriate to model sandpiles than stochastic systems or deterministic systems in which discontinuities are the only nonlinearity. In particular, we are able to reproduce the breakdown of self-organized criticality found in two well known experiments, that is, a centrally fueled pile [Phys. Rev. Lett. 65 (1990) 1120] and sand in a rotating tray [Phys. Rev. Lett. 69 (1992) 2431]. By varying the parameters of the model we recover self-organized criticality, in agreement with other experiments and other models. We show that chaos plays a fundamental role in the dynamics of the system.