Showing papers in "Annalen der Physik in 2018"

Non‐Hermitian Gauged Topological Laser Arrays

Abstract: Stable and phase-locked emission in an extended topological supermode of coupled laser arrays, based on concepts of non-Hermitian and topological photonics, is theoretically suggested. We consider a non-Hermitian Su-Schrieffer-Heeger chain of coupled microring resonators and show that application of a synthetic imaginary gauge field via auxiliary passive microrings leads to all supermodes of the chain, except one, to become edge states. The only extended supermode, that retains some topological protection, can stably oscillate suppressing all other non-topological edge supermodes. Numerical simulations based on a rate equation model of semiconductor laser arrays confirm stable anti-phase laser emission in the extended topological supermode and the role of the synthetic gauge field to enhance laser stability.

Astrophysical Black Holes: A Compact Pedagogical Review

Abstract: Black holes are among the most extreme objects that can be found in the Universe andan ideal laboratory for testing fundamental physics. Here, the basic properties ofblack holes as expected from general relativity, the main astronomical observations,and the leading astrophysical techniques to probe the strong gravity region of theseobjects are reviewed. The main intention is to provide a compact introductory overviewon astrophysical black holes to new students entering this research field, as wellas to senior researchers working in general relativity and alternative theories ofgravity, who wish to quickly learn the state of the art of astronomical observationsof black holes.

Freeform Metagratings Based on Complex Light Scattering Dynamics for Extreme, High Efficiency Beam Steering

Abstract: Conventional phased-array metasurfaces utilize resonant nanoparticles or nanowaveguides to specify spatially-dependent amplitude and phase responses to light. In nearly all these implementations, subwavelength-scale elements are stitched together while minimizing coupling between adjacent elements. In this report, we theoretically analyze an alternate method of metasurface design, utilizing freeform inverse design methods, which support significantly enhanced efficiencies compared to conventional designs. Our design process optimizes wavelength-scale elements, which dramatically increases the design space for optical engineering. An in-depth coupled mode analysis of ultra-wide-angle beam deflectors and wavelength splitters shows that the extraordinary performance of our designs originates from the large number of propagating modes supported by the metagrating, in combination with complex multiple scattering dynamics exhibited by these modes. We also apply our coupled mode analysis to conventional nanowaveguide-based metasurfaces to understand and quantify the factors limiting the efficiencies of these devices. We envision that freeform metasurface design methods will open new avenues towards truly high-performance, multi-functional optics by utilizing strongly coupled nanophotonic modes and elements.

FFLO States in Layered Organic Superconductors

Abstract: In this short review, the recently found experimental evidence that Fulde–Ferrell–Larkin–Ovchinnikov (FFLO) states are realized in quasi-two-dimensional (2D) organic superconductors is reported. At low temperatures and when a high magnetic field is aligned parallel to the conducting organic layers, an upturn of the upper critical field much beyond the Pauli limit is observed, as proven by thermodynamic measurements. Under certain conditions, a second thermodynamic transition emerges inside the FFLO state. Nuclear magnetic resonance (NMR) work has added strong microscopic support for the realization of the FFLO state. The NMR spectra in the FFLO phase can very well be explained by a nonuniform one-dimensionally modulated superconducting order parameter. All these features, appearing only in a very narrow angular region close to parallel-field orientation, give robust evidence for the realization of the FFLO state in organic superconductors.

Effects of Hawking Radiation on the Entropic Uncertainty in a Schwarzschild Space‐Time

Abstract: Heisenberg uncertainty principle describes a basic restriction on observer's ability of precisely predicting the measurement for a pair of non-commuting observables, and virtually is at the core of quantum mechanics. We herein aim to study entropic uncertainty relation under the background of the Schwarzschild black hole and its control. Explicitly, we develop dynamical features of the measuring uncertainty via entropy in a practical model where a stationary particle interacts with its surrounding environment while another particle --- serving as a quantum memory reservoir --- undergoes freefall in the vicinity of the event horizon of the Schwarzschild space-time. It shows higher Hawking temperatures would give rise to an inflation of the entropic uncertainty on the measured particle. This is suggestive the measurement uncertainty is strongly correlated with degree of mixing present in the evolving particles. Additionally, based on information flow theory, we provide a physical interpretation for the observed dynamical behaviors related with the entropic uncertainty in such a realistic scenario. Finally, an efficient strategy is proposed to reduce the uncertainty by non-tracing-preserved operations. Therefore, our explorations may improve the understanding of the dynamic entropic uncertainty in a curved space-time, and illustrate predictions of quantum measurements in relativistic quantum information sciences.

Photonic Hook Plasmons: A New Curved Surface Wave

Abstract: It ia well-known that surface plasmon wave propagates along a straight line, but this common sense was broken by the artificial curved light - plasmon Airy beam. In this paper we introduce a new class of curved surface plasmon wave - the photonic hook plasmon. It propagates along wavelength scaled curved trajectory with radius less than surface plasmon polariton wavelength, and can exist despite the strong energy dissipation at the metal surface.

Questioning the Recent Observation of Quantum Hawking Radiation

Abstract: A recent article [J. Steinhauer, Nat. Phys. 12, 959 (2016)] has reported the observation of quantum Hawking radiation and its entanglement in an analogue black hole. This paper analyses the published evidence, its consistency with theoretical bounds and the statistical significance of the results. The analysis raises severe doubts on the observation of Hawking radiation.

Is Teleparallel Gravity Really Equivalent to General Relativity

Abstract: Fil: Combi, Luciano. Provincia de Buenos Aires. Gobernacion. Comision de Investigaciones Cientificas. Instituto Argentino de Radioastronomia. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - La Plata. Instituto Argentino de Radioastronomia; Argentina

Holographical aspects of dyonic black holes: Massive gravity generalization

Abstract: The content of this paper includes studying holographical and thermodynamical aspects of dyonic black holes in the presence of massive gravity. For the first part of paper, thermodynamical properties of the bulk which includes black holes are studied and the main focus is on critical behavior. It will be shown that the existence of massive gravitons introduces remnant for temperature after evaporation of black holes, van der Waals phase transition for non-spherical black holes and etc. The consistency of different thermodynamical approaches toward critical behavior of the black holes is presented and the physical properties near the region of thermal instability are given. Next part of the paper studies holographical aspects of the boundary theory. Magnetization and susceptibility of the boundary are extracted and the conditions for having diamagnetic and paramagnetic behaviors are investigated. It will be shown that generalization to massive gravity results into the existence of diamagnetic/paramagnetic phases in phase structure of the hyperbolic and horizon flat of boundary conformal field theory.

Intensity‐Enhanced Apodization Effect on an Axially Illuminated Circular‐Column Particle‐Lens

Abstract: A particle can function as a refractive lens to focus a plane wave, generating a narrow, high intensive, weak-diverging beam within a sub-wavelength volume, known as the ‘photonic nanojet’. It is known that apodization method, in the form of an amplitude pupil-mask centrally situated on a particle-lens, can further reduce the waist of a photonic nanojet, however, it usually lowers the intensity at the focus due to blocking the incident light. In this paper, the anomalously intensity-enhanced apodization effect was discovered for the first time via numerical simulation of focusing of the axially illuminated circular-column particle-lenses, and a greater than 100% peak intensity increase was realised for the produced photonic nanojets.

The Chern‐Simons Current in Systems of DNA‐RNA Transcriptions

Abstract: A Chern-Simons current, coming from ghost and anti-ghost fields of supersymmetry theory, can be used to define a spectrum of gene expression in new time series data where a spinor field, as alternative representation of a gene, is adopted instead of using the standard alphabet sequence of bases $A, T, C, G, U$. After a general discussion on the use of supersymmetry in biological systems, we give examples of the use of supersymmetry for living organism, discuss the codon and anti-codon ghost fields and develop an algebraic construction for the trash DNA, the DNA area which does not seem active in biological systems. As a general result, all hidden states of codon can be computed by Chern-Simons 3 forms. Finally, we plot a time series of genetic variations of viral glycoprotein gene and host T-cell receptor gene by using a gene tensor correlation network related to the Chern-Simons current. An empirical analysis of genetic shift, in host cell receptor genes with separated cluster of gene and genetic drift in viral gene, is obtained by using a tensor correlation plot over time series data derived as the empirical mode decomposition of Chern-Simons current.

Wide-Bandpass Filtering Due to Multipole Resonances of Spoof Localized Surface Plasmons

Abstract: We propose wideband bandpass filters based on multipole resonances of spoof localized surface plasmons (SLSPs). The resonance characteristics and geometric tunability of SLSPs are investigated under microstrip excitations. Strong coupling with interlayer microstrip lines is proposed to join discrete multipole resonances into a continuous and flat passband. The SLSP filters exhibit wide passbands in compact sizes and well-balanced shapes, while holding satisfactory spurious rejection bands, group delays, and geometric tunability. This work exposes the SLSPs' application potential in filters as novel resonators.

Dynamics and Recovery of Genuine Multipartite Einstein–Podolsky–Rosen Steering and Genuine Multipartite Nonlocality for a Dissipative Dirac System via the Unruh Effect

Abstract: In this paper, we investigate the dynamics behaviors of genuine multipartite Einstein-Podolsky-Rosen steering (GMS) and genuine multipartite nonlocality (GMN), and explore how to recover the lost GMS and GMN under a decoherence mixture system. Explicitly, the mixed decoherence system can be modeled by that a tripartite Werner-type state suffers from the non-Markovian regimes and one subsystem of the tripartite is under non-inertial frame. The conditions for steerable and nonlocal states can be obtained with respect to the tripartite Werner-type state established initially. GMS and GMN are very fragile and vulnerable under the influence of the collective decoherence. GMS and GMN will vanish with growing intensity of Unruh effect and the non-Markovian reservoir. If the GMS and GMN could achieve again with the increase of {\\gamma}_0t, only if the value of {\\lambda}/{\\gamma}_0 is small enough.Besides, all achievable GMN's states are steerable, while not every steerable state (GMS's state) can achieve nonlocality. It means that the steering-nonlocality hierarchy is still tenable and GMN's states are a strict subset of the GMS's states in such a scenario. Subsequently, we put forward an available methodology to recover the lost GMS and GMN. It turns out that the lost GMS and GMN can be effectively restored, and the ability of GMS and GMN to suppress the collective decoherence can be enhanced.

Bright‐Dark Rogue Waves

Abstract: During the last two decades, revealing mechanisms of origin waves with anomalous amplitude (rogue waves) have been in the focus of researchers from different fields ranging from oceanography to laser physics. Mode-locked lasers, as a test bed system, provide a unique opportunity to collect more dataon rogue waves in the form of random pulses (soliton rain) and to clarify the mechanisms of rogue-wave emergence caused by soliton–soliton and soliton–dispersive wave interactions. Here, for the first time, for an Er-doped mode-locked laser, a new type of vector rogue waves is demonstrated experimentally and theoretically, which is driven by desynchronization of the orthogonal linear states of polarization, so leading to output power oscillations in the form of anomalous spikes-dips (bright-dark rogue waves).The results can pave the way to unlocking the universal nature of the origin of rogue waves and thus can be of interest to the broad scientific community.

Quantum Information Measures of the One‐Dimensional Robin Quantum Well

Abstract: Shannon quantum information entropies $S_{x,k}$, Fisher informations $I_{x,k}$, Onicescu energies $O_{x,k}$ and statistical complexities $e^{S_{x,k}}O_{x,k}$ are calculated both in the position (subscript $x$) and momentum ($k$) representations for the Robin quantum well characterized by the extrapolation lengths $\Lambda_-$ and $\Lambda_+$ at the two confining surfaces. The analysis concentrates on finding and explaining the most characteristic features of these quantum information measures in the whole range of variation of the Robin distance $\Lambda$ for the symmetric, $\Lambda_-=\Lambda_+=\Lambda$, and antisymmetric, $\Lambda_-=-\Lambda_+=\Lambda$, geometries. Analytic results obtained in the limiting cases of the extremely large and very small magnitudes of the extrapolation parameter are corroborated by the exact numerical computations that are extended to the arbitrary length $\Lambda$. It is confirmed, in particular, that the entropic uncertainty relation $S_{x_n}+S_{k_n}\geq1+\ln\pi$ and general inequality $e^SO\geq1$, which is valid both in the position and momentum spaces, hold true at any Robin distance and for every quantum state $n$. For either configuration, there is a range of the extrapolation lengths where the rule $S_{x_{n+1}}(\Lambda)+S_{k_{n+1}}(\Lambda)\geq S_{x_n}(\Lambda)+S_{k_n}(\Lambda)$ that is correct for the Neumann ($\Lambda=\infty$) or Dirichlet ($\Lambda=0$) boundary conditions, is violated. Other analytic and numerical results for all measures are discussed too and their physical meaning is highlighted.

Electronic Properties of Strained Double‐Weyl Systems

Abstract: The effects of strains on the low-energy electronic properties of double-Weyl phases are studied in solids and cold-atom optical lattices. The principal finding is that deformations do not couple, in general, to the low-energy effective Hamiltonian as a pseudoelectromagnetic gauge potential. The response of an optical lattice to strains is simpler, but still only one of several strain-induced terms in the corresponding low-energy Hamiltonian can be interpreted as a gauge potential. Most interestingly, the strains can induce a nematic order parameter that splits a double-Weyl node into a pair of Weyl nodes with the unit topological charges. The effects of deformations on the motion of wavepackets in the double-Weyl optical lattice model are studied. It is found that, even in the undeformed lattices, the wavepackets with opposite topological charges can be spatially split. Strains, however, modify their velocities in a very different way and lead to a spin polarization of the wavepackets.

Improving Shortcuts to Non‐Hermitian Adiabaticity for Fast Population Transfer in Open Quantum Systems

Abstract: It is still a challenge to experimentally realize shortcuts to adiabaticity (STA) for a non-Hermitian quantum system since a non-Hermitian quantum system's counterdiabatic driving Hamiltonian contains some unrealizable auxiliary control fields. In this paper, we relax the strict condition in constructing STA and propose a method to redesign a realizable supplementary Hamiltonian to construct non-Hermitian STA. The redesigned supplementary Hamiltonian can be eithersymmetric or asymmetric. For the sake of clearness, we apply this method to an Allen-Eberly model as an example to verify the validity of the optimized non-Hermitian STA. The numerical simulation demonstrates that a ultrafast population inversion could be realized in a two-level non-Hermitian system.