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  • Propagation and ramification of a solitary pulse through an environmentally coupled qubit
    New J. Phys. (IF 3.539) Pub Date : 2020-10-18
    Yibo Gao, Shijie Jin and Hou Ian

    We compute the relaxations experienced by a superconducting qubit and the simultaneous variation induced on the shape of a microwave pulse during the propagation of the pulse through the qubit. The environmentally affected propagation and the dressed relaxations are accounted by a microscopic-master-Maxwell equation pair. It is shown that the qubit longitudinal relaxation vanishes when the pulse envelope

    更新日期:2020-10-19
  • Thermodynamics of optical Bloch equations
    New J. Phys. (IF 3.539) Pub Date : 2020-10-18
    Cyril Elouard, David Herrera-Martí, Massimiliano Esposito and Alexia Auffèves

    Optical Bloch equations (OBE) describe the coherent exchange of energy between a quantum bit (qubit) and a quasi-resonant driving field in the presence of a thermal bath. Despite it being an ubiquitous process in quantum technologies, a sound thermodynamic analysis is still missing. We hereby provide such an analysis, by deriving the relevant framework from first principles. We start from a complete

    更新日期:2020-10-19
  • Exact lattice-model calculation of boundary modes for Weyl semimetals and graphene
    New J. Phys. (IF 3.539) Pub Date : 2020-10-18
    Vardan Kaladzhyan, Sarah Pinon, Jens H Bardarson and Cristina Bena

    We provide an exact analytical technique to obtain within a lattice model the wave functions of the edge states in zigzag- and bearded-edge graphene, as well as of the Fermi-arc surface states in Weyl semimetals described by a minimal bulk model. We model the corresponding boundaries as an infinite scalar potential localized on a line, and respectively within a plane. We use the T -matrix formalism

    更新日期:2020-10-19
  • Terahertz pulse generation by two-color laser fields with circular polarization
    New J. Phys. (IF 3.539) Pub Date : 2020-10-15
    C Tailliez, A Stathopulos, S Skupin, D Buožius, I Babushkin, V Vaičaitis and L Bergé

    We study the influence of the polarization states of ionizing femtosecond two-color pulses on the emitted terahertz radiation in gases. A local-current model and plane-wave evaluations justify the previously-reported impact on the THz energy yield and a (almost) linearly-polarized THz field when using circularly-polarized laser harmonics. For such pump pulses, the THz yield is independent of the relative

    更新日期:2020-10-19
  • Production of energetic protons, deuterons, and neutrons up to 60 MeV via disruption of a current-carrying plasma column at 3 MA
    New J. Phys. (IF 3.539) Pub Date : 2020-10-15
    D Klir, A V Shishlov, V A Kokshenev, S L Jackson, K Rezac, R K Cherdizov, J Cikhardt, G N Dudkin, F I Fursov, J Krasa, J Kravarik, P Kubes, N E Kurmaev, V Munzar, N A Ratakhin, K Turek and V A Varlachev

    Acceleration of ions to multi-MeV energies is investigated in various plasma devices to better understand processes in astrophysical plasmas and to develop efficient accelerators for a variety of applications. This paper reports the production of proton, deuteron, and electron beams in a z-pinch—a cylindrically symmetric plasma column that is compressed by its own magnetic field. For this work, the

    更新日期:2020-10-19
  • Circularly polarized coherent light-induced boosting of polymer solar cells photovoltaic performance
    New J. Phys. (IF 3.539) Pub Date : 2020-10-15
    Longlong Zhang, Yuying Hao, Wei Qin, Shijie Xie and Fanyao Qu

    We report a microscopic quantum theory which can be used to study circularly polarized light (CPL) induced singlet to triplet conversions in polymer solar cells (PSCs). We demonstrate that by properly adjusting CPL irradiation parameters, the photo-created singlet excitons can be efficiently converted into non radiative triplet excitons. The maximum singlet–triplet conversion ratio might be reached

    更新日期:2020-10-19
  • Simulating extremal temporal correlations
    New J. Phys. (IF 3.539) Pub Date : 2020-10-15
    Cornelia Spee, Costantino Budroni and Otfried Gühne

    The correlations arising from sequential measurements on a single quantum system form a polytope. This is defined by the arrow-of-time (AoT) constraints, meaning that future choices of measurement settings cannot influence past outcomes. We discuss the resources needed to simulate the extreme points of the AoT polytope, where resources are quantified in terms of the minimal dimension, or ‘internal

    更新日期:2020-10-19
  • Mitigating decoherence in hot electron interferometry
    New J. Phys. (IF 3.539) Pub Date : 2020-10-14
    Lewis A Clark, Masaya Kataoka and Clive Emary

    Due to their high energy, hot electrons in quantum Hall edge (QHE) states can be considered as single particles that have the potential to be used for quantum optics-like experiments. Unlike photons, however, electrons typically undergo scattering processes in transport, which results in a loss of coherence and limits their ability to show quantum-coherent behaviour. Here we study theoretically the

    更新日期:2020-10-16
  • Topologically nontrivial interband plasmons in type-II Weyl semimetal MoTe 2
    New J. Phys. (IF 3.539) Pub Date : 2020-10-14
    Xun Jia, Maoyuan Wang, Dayu Yan, Siwei Xue, Shuyuan Zhang, Jianhui Zhou, Youguo Shi, Xuetao Zhu, Yugui Yao and Jiandong Guo

    In many realistic topological materials, more than one kind of fermions contribute to the electronic bands crossing the Fermi level, leading to various novel phenomena. Here, using momentum-resolved inelastic electron scattering, we investigate the plasmons and their evolution across the phase transition in a type-II Weyl semimetal MoTe 2 , in which both Weyl fermions and trivial electrons contribute

    更新日期:2020-10-16
  • Decreased resilience in power grids under dynamically induced vulnerabilities
    New J. Phys. (IF 3.539) Pub Date : 2020-10-14
    C C Galindo-González, D Angulo-Garcia and G Osorio

    In this paper, a methodology inspired on bond and site percolation methods is applied to the estimation of the resilience against failures in power grids. Our approach includes vulnerability measures with both dynamical and structural foundations as an attempt to find more insights about the relationships between topology and dynamics in the second-order Kuramoto model on complex networks. As test

    更新日期:2020-10-16
  • From the open generalized Heisenberg model to the Landau–Lifshitz equation
    New J. Phys. (IF 3.539) Pub Date : 2020-10-14
    Ariel Norambuena, Andrés Franco and Raúl Coto

    Magnetic systems can be described by the classical Landau–Lifshitz (LL) equation or the fully quantum open generalized Heisenberg model. Using the Lindblad master equation and the mean-field approximation, we demonstrate that the open generalized Heisenberg model is reduced to a generalized LL equation. The open dynamic is modeled using spin-boson interactions with a common bosonic reservoir at thermal

    更新日期:2020-10-16
  • Minimal informationally complete measurements for probability representation of quantum dynamics
    New J. Phys. (IF 3.539) Pub Date : 2020-10-14
    V I Yashin, E O Kiktenko, A S Mastiukova and A K Fedorov

    In the present work, we suggest an approach for describing dynamics of finite-dimensional quantum systems in terms of pseudostochastic maps acting on probability distributions, which are obtained via minimal informationally complete quantum measurements. The suggested method for probability representation of quantum dynamics preserves the tensor product structure, which makes it favourable for the

    更新日期:2020-10-16
  • Dual-frequency on–off modulation and slow light analysis based on dual plasmon-induced transparency in terahertz patterned graphene metamaterial
    New J. Phys. (IF 3.539) Pub Date : 2020-10-14
    Min Li, Hongjian Li, Hui Xu, Cuixiu Xiong, Mingzhuo Zhao, Chao Liu, Banxian Ruan, Baihui Zhang and Kuan Wu

    A dual-frequency on–off modulator with considerable modulation depth (MD) and relatively low insertion loss (IL) is performed with patterned monolayer graphene metamaterial. Destructive interference in this structure gives rise to the dual plasmon-induced transparency (DPIT) phenomenon. The coupled mode theory, confirmed by simulated values, is comprehensively introduced to expound the physical mechanism

    更新日期:2020-10-16
  • From the Jaynes–Cummings model to non-abelian gauge theories: a guided tour for the quantum engineer
    New J. Phys. (IF 3.539) Pub Date : 2020-10-12
    Valentin Kasper, Gediminas Juzeliūnas, Maciej Lewenstein, Fred Jendrzejewski and Erez Zohar

    The design of quantum many body systems, which have to fulfill an extensive number of constraints, appears as a formidable challenge within the field of quantum simulation. Lattice gauge theories are a particular important class of quantum systems with an extensive number of local constraints and play a central role in high energy physics, condensed matter and quantum information. Whereas recent experimental

    更新日期:2020-10-13
  • Ultrafast dynamics and evolution of ion-induced opacity in transparent dielectrics
    New J. Phys. (IF 3.539) Pub Date : 2020-10-12
    M Coughlan, H Donnelly, N Breslin, C Arthur, G Nersisyan, M Yeung, B Villagomez-Bernabe, M Afshari, F Currell, M Zepf and B Dromey

    Recently, measurements of few-picosecond (ps, 10 −12 s) pulses of laser-driven protons were realised by the observation of transient opacity in SiO 2 . This ultrafast response could be understood by the formation of self-trapped excitonic states in the material, creating a rapid de-excitation channel for conduction band electrons. Here we extend this work to examine the onset and evolution of an ion-induced

    更新日期:2020-10-13
  • Gratings with longitudinal variations in coupling coefficients: super-efficiency and unidirectionality in distributed feedback Raman fiber lasers
    New J. Phys. (IF 3.539) Pub Date : 2020-10-12
    Amirhossein Tehranchi and Raman Kashyap

    We propose a technique to design highly-efficient and -unidirectional DFB Raman fiber lasers based on the engineering of the grating’s coupling coefficient including a π -phase shift position in the fiber. For this purpose, first the ideal intra-cavity signal powers for different pump power levels are determined for given fiber lengths. Then, the sum and difference between the counter-propagating wave

    更新日期:2020-10-13
  • Bistability of Bose–Fermi mixtures
    New J. Phys. (IF 3.539) Pub Date : 2020-10-12
    Tomasz Karpiuk, Mariusz Gajda and Miros∤aw Brewczyk

    We study formation of a Bose–Fermi droplet in realistic experimental setting. We start with a typical experimental arrangement of two atomic species—bosons and fermions in a harmonic axially symmetric confinement. The variational analysis shows that the system exhibits bistability. For weak repulsion between bosons, one of the equilibrium states, smaller in size, spherically symmetric, and with negative

    更新日期:2020-10-13
  • Ultra-fast two-qubit ion gate using sequences of resonant pulses
    New J. Phys. (IF 3.539) Pub Date : 2020-10-12
    E Torrontegui, D Heinrich, M I Hussain, R Blatt and J J García-Ripoll

    We propose a new protocol to implement ultra-fast two-qubit phase gates with trapped ions using spin-dependent kicks induced by resonant transitions. By only optimizing the allocation of the arrival times in a pulse train sequence the gate is implemented in times faster than the trapping oscillation period T < 2 π / ω . Such gates allow us to increase the number of gate operations that can be completed

    更新日期:2020-10-13
  • Nanocluster glass-formation: a potential energy landscape perspective
    New J. Phys. (IF 3.539) Pub Date : 2020-10-12
    D Y Sun and X G Gong

    The intrinsic nature of glass states or glass transitions has been a mystery for a long time. Recent studies have suggested that glass-formation versus crystallization occurs for potential energy landscapes (PEL) having a specific structure and the present work is an elaboration of this perspective. To explore how the flatness of the PEL related to glass transition, we develop a method to adjust the

    更新日期:2020-10-13
  • A quantum heat machine from fast optomechanics
    New J. Phys. (IF 3.539) Pub Date : 2020-10-12
    James S Bennett, Lars S Madsen, Halina Rubinsztein-Dunlop and Warwick P Bowen

    We consider a thermodynamic machine in which the working fluid is a quantized harmonic oscillator that is controlled on timescales that are much faster than the oscillator period. We find that operation in this ‘fast’ regime allows access to a range of quantum thermodynamical behaviors that are otherwise inaccessible, including heat engine and refrigeration modes of operation, quantum squeezing, and

    更新日期:2020-10-13
  • How magnetic field can transform a superconductor into a Bose metal
    New J. Phys. (IF 3.539) Pub Date : 2020-10-12
    Tianhao Ren and Alexei M Tsvelik

    We discuss whether a simple theory of superconducting stripes coupled by Josephson tunneling can describe a metallic transport, once the coherent tunneling of pairs is suppressed by the magnetic field. For a clean system, the conclusion we reached is negative: the excitation spectrum of preformed pairs consists of Landau levels, and once the magnetic field exceeds a critical value, the transport becomes

    更新日期:2020-10-13
  • An analytical velocity field of spiral tips in reaction–diffusion systems
    New J. Phys. (IF 3.539) Pub Date : 2020-10-11
    De-Bei Pan, Bing-Wei Li, Jun-Ting Pan, Qi-Hao Li and Hong Zhang

    Spiral waves are ubiquitous in diverse physical, chemical, and biological systems. The tip (phase singularity) of a spiral wave is considered to represent its organizing center. Here, we derive an analytical velocity field of spiral tips based on the variables of a general two-variable reaction–diffusion (RD) equation. From this velocity field, we can predict the velocities of spiral tips at time t

    更新日期:2020-10-12
  • Twin-field quantum key distribution with passive-decoy state
    New J. Phys. (IF 3.539) Pub Date : 2020-10-08
    Jun Teng, Feng-Yu Lu, Zhen-Qiang Yin, Guan-Jie Fan-Yuan, Rong Wang, Shuang Wang, Wei Chen, Wei Huang, Bing-Jie Xu, Guang-Can Guo and Zheng-Fu Han

    Twin-Field quantum key distribution (TF-QKD) and its variants, e.g. phase-maching QKD, sending-or-not-sending QKD, and no phase post-selection TFQKD promise high key rates at long distance to beat the rate distance limit without a repeater. The security proof of these protocols are based on decoy-state method, which is usually performed by actively modulating a variable optical attenuator together

    更新日期:2020-10-12
  • On space charge effects in laboratory-based photoemission electron microscopy using compact gas discharge extreme ultraviolet sources
    New J. Phys. (IF 3.539) Pub Date : 2020-10-08
    Daniel Wilson, Christoph Schmitz, Denis Rudolf, Carsten Wiemann, Claus M Schneider and Larissa Juschkin

    The analysis of electronic and structural properties of surfaces has been greatly advanced by photoemission electron microscopy and spectroscopy techniques. To further improve lateral and energy resolution of the instruments, it is necessary to optimize parameters of the radiation sources employed for photoemission studies (e.g. photon flux, pulse duration, spot size etc). We studied space charge effects

    更新日期:2020-10-12
  • Current propagation behaviors and spin filtering effects in three-terminal topological-insulator junctions
    New J. Phys. (IF 3.539) Pub Date : 2020-10-08
    Jia-En Yang, Xiao-Long Lü and Hang Xie

    Understand the spin and current behavior in the topological-insulator (TI) system is crucial for the design of electronic and spintronic devices. To study these behaviors, some three-terminal hetero-junction TI systems made from the zigzag silicene-like nanoribbons (ZSiNRs) are investigated. Different external fields are applied in the leads and conductor regions, which result in the expected topological

    更新日期:2020-10-12
  • Loss tolerant quantum absorption measurement
    New J. Phys. (IF 3.539) Pub Date : 2020-10-08
    Ryo Okamoto, Yuta Tokami and Shigeki Takeuchi

    The quantum statistics of entangled photon pairs promise greater performance for absorption measurements than can be achieved classically. However, the performance of a quantum approach is easily degraded under a loss of photons caused by experimental limitations. Here, we propose a loss-tolerant quantum scheme using quantum destructive interference in a nonlinear interferometer. Our theoretical results

    更新日期:2020-10-12
  • On the long-term stability of space-time crystals
    New J. Phys. (IF 3.539) Pub Date : 2020-10-08
    J Smits, H T C Stoof and P van der Straten

    We investigate a space-time crystal in a superfluid Bose gas. Using a well-controlled periodic drive we excite only one crystalline mode in the system, which can be accurately modeled in the rotating frame of the drive. Using holographic imaging we observe the stability of the crystal over an extended period of time and show the robustness of its structure in both space and time. By introducing a fourth-order

    更新日期:2020-10-12
  • Stable two-dimensional soliton complexes in Bose–Einstein condensates with helicoidal spin–orbit coupling
    New J. Phys. (IF 3.539) Pub Date : 2020-10-07
    Y V Kartashov, E Ya Sherman, B A Malomed and V V Konotop

    We show that attractive two-dimensional (2D) spinor Bose–Einstein condensates with helicoidal spatially periodic spin–orbit coupling (SOC) support a rich variety of stable fundamental solitons and bound soliton complexes. Such states exist with chemical potentials belonging to the semi-infinite gap in the band spectrum created by the periodically modulated SOC. All these states exist above a certain

    更新日期:2020-10-08
  • Polarization-gradient cooling of 1D and 2D ion Coulomb crystals
    New J. Phys. (IF 3.539) Pub Date : 2020-10-07
    M K Joshi, A Fabre, C Maier, T Brydges, D Kiesenhofer, H Hainzer, R Blatt and C F Roos

    We present experiments on polarization gradient cooling of Ca + multi-ion Coulomb crystals in a linear Paul trap. Polarization gradient cooling of the collective modes of motion whose eigenvectors have overlap with the symmetry axis of the trap is achieved by two counter-propagating laser beams with mutually orthogonal linear polarizations that are blue-detuned from the S 1/2 ↔ P 1/2 transition. We

    更新日期:2020-10-08
  • Tilted double Dirac cone and anisotropic quantum-spin-Hall topological insulator in mechanical granular graphene
    New J. Phys. (IF 3.539) Pub Date : 2020-10-07
    Li-Yang Zheng, Georgios Theocharis, Romain Fleury, Vincent Tournat and Vitalyi Gusev

    Dirac degeneracies are essential ingredients to control topological charge exchanges between bands and trigger the unique edge transport properties of topological materials. In addition, when Dirac cones are tilted, exotic phenomena can emerge such as anomalous Hall effect or unconventional Klein tunneling. However, the unique topological transport properties arising from the opening of tilted Dirac

    更新日期:2020-10-08
  • Target finding in fibrous biological environments
    New J. Phys. (IF 3.539) Pub Date : 2020-10-06
    David Gomez, Eial Teomy, Ayelet Lesman and Yair Shokef

    We use a lattice model to study first-passage time distributions of target finding events through complex environments with elongated fibers distributed with different anisotropies and volume occupation fractions. For isotropic systems and for low densities of aligned fibers, the three-dimensional search is a Poisson process with the first-passage time exponentially distributed with the most probable

    更新日期:2020-10-07
  • Emergent pattern formation of active magnetic suspensions in an external field
    New J. Phys. (IF 3.539) Pub Date : 2020-10-06
    Fabian R Koessel and Sara Jabbari-Farouji

    We study collective self-organization of weakly magnetic active suspensions in a uniform external field by analyzing a mesoscopic continuum model that we have recently developed. Our model is based on a Smoluchowski equation for a particle probability density function in an alignment field coupled to a mean-field description of the flow arising from the activity and the alignment torque. Performing

    更新日期:2020-10-07
  • Many-body interference in bosonic dynamics
    New J. Phys. (IF 3.539) Pub Date : 2020-10-05
    Gabriel Dufour, Tobias Brünner, Alberto Rodríguez and Andreas Buchleitner

    We develop a framework to systematically investigate the influence of many-particle interference on the dynamics of generic—possibly interacting—bosonic systems. We consider mixtures of bosons which belong to several distinguishable species, allowing us to tune the level of many-particle interference, and identify the corresponding signatures in the time-dependent expectation values of observables

    更新日期:2020-10-06
  • A non-Hermitian PT -symmetric kicked top
    New J. Phys. (IF 3.539) Pub Date : 2020-10-05
    Steve Mudute-Ndumbe and Eva-Maria Graefe

    A non-Hermitian PT -symmetric version of the kicked top is introduced to study the interplay of quantum chaos with balanced loss and gain. The classical dynamics arising from the quantum dynamics of the angular momentum expectation values are derived. It is demonstrated that the presence of PT -symmetry can lead to ‘stable’ mixed regular chaotic behaviour without sinks or sources for subcritical values

    更新日期:2020-10-06
  • Strong connection between single-particle and density excitations in Bose–Einstein condensates
    New J. Phys. (IF 3.539) Pub Date : 2020-10-05
    Shohei Watabe

    Strong connection between the single-particle excitation and the collective excitation stands out as one of the features of Bose–Einstein condensates (BECs). We discuss theoretically these single-particle and density excitations of BECs focusing on the exact properties of the one-body and two-body Green’s functions developed by Gavoret and Nozières. We also investigate these excitations by using the

    更新日期:2020-10-06
  • Suppressing excess noise for atmospheric continuous-variable quantum key distribution via adaptive optics approach
    New J. Phys. (IF 3.539) Pub Date : 2020-10-04
    Geng Chai, Peng Huang, Zhengwen Cao and Guihua Zeng

    The excess noise inducing in the process of the quantum communication procedure is the major obstacle restricting the performance of continuous-variable quantum key distribution (CVQKD). In order to effectively suppress the excess noise through correcting the propagation-induced distortions on the quality of the propagated quantum signal, we propose a general scheme of suppressing excess noise for

    更新日期:2020-10-05
  • Finite-key analysis for memory-assisted decoy-state quantum key distribution
    New J. Phys. (IF 3.539) Pub Date : 2020-10-04
    Guillermo Currás Lorenzo and Mohsen Razavi

    Memory-assisted quantum key distribution (MA-QKD) systems are among novel promising solutions that can improve the key-rate scaling with channel loss. By using a middle node with quantum storage and measurement functionalities, they offer the same key-rate scaling with distance as a single-node quantum repeater. However, the distance at which they can surpass the nominal key rate of repeaterless systems

    更新日期:2020-10-05
  • Multiple-scattering approach for multi-spin chiral magnetic interactions: application to the one- and two-dimensional Rashba electron gas
    New J. Phys. (IF 3.539) Pub Date : 2020-09-30
    Samir Lounis

    Various multi-spin magnetic exchange interactions (MEI) of chiral nature have been recently unveiled. Owing to their potential impact on the realisation of twisted spin-textures, their future implication in spintronics or quantum computing is very promising. Here, I address the long-range behavior of multi-spin MEI on the basis of a multiple-scattering formalism implementable in Green functions based

    更新日期:2020-10-02
  • Emitter-site specificity of hard x-ray photoelectron Kikuchi-diffraction
    New J. Phys. (IF 3.539) Pub Date : 2020-09-30
    O Fedchenko, A Winkelmann, S Chernov, K Medjanik, S Babenkov, S Y Agustsson, D Vasilyev, M Hoesch, H-J Elmers and G Schönhense

    High-resolution full-field imaging of ( k x , k y ) photoelectron distributions ( k -resolution 0.03 Å −1 , angular resolution 0.03° at 6.7 keV) in a large field of view (up to 16 Å −1 dia.) allows to observe fine details in Kikuchi-type diffractograms. Alongside with the element specificity via core-level spectra, this method opens a new avenue to structural analysis using hard x-ray photoelectron

    更新日期:2020-10-02
  • From single-particle stochastic kinetics to macroscopic reaction rates: fastest first-passage time of N random walkers
    New J. Phys. (IF 3.539) Pub Date : 2020-09-30
    Denis S Grebenkov, Ralf Metzler and Gleb Oshanin

    We consider the first-passage problem for N identical independent particles that are initially released uniformly in a finite domain Ω and then diffuse toward a reactive area Γ, which can be part of the outer boundary of Ω or a reaction centre in the interior of Ω. For both cases of perfect and partial reactions, we obtain the explicit formulas for the first two moments of the fastest first-passage

    更新日期:2020-10-02
  • Extreme renormalisations of dimer eigenmodes by strong light–matter coupling
    New J. Phys. (IF 3.539) Pub Date : 2020-09-30
    Thomas J Sturges, Taavi Repän, Charles A Downing, Carsten Rockstuhl and Magdalena Stobińska

    We explore by theoretical means an extreme renormalisation of the eigenmodes of a dimer of dipolar meta-atoms due to strong light–matter interactions. Firstly, by tuning the height of an enclosing photonic cavity, we can lower the energy level of the symmetric ‘bright’ mode underneath that of the anti-symmetric ‘dark’ mode. This is possible due to the polaritonic nature of the symmetric mode, that

    更新日期:2020-10-02
  • Noise-induced stabilization of saddle-node ghosts
    New J. Phys. (IF 3.539) Pub Date : 2020-09-29
    Josep Sardanyés, Carles Raich and Tomás Alarcón

    It is known that saddle-node (s-n) bifurcations leave a saddle remnant (or ghost) in the region of the phase space where the annihilation of the fixed points occurred. The corresponding time delay, t d , found right after the bifurcation is known to follow the scaling law ##IMG## [http://ej.iop.org/images/1367-2630/22/9/093064/njpabb549ieqn1.gif] {${t}_{\mathrm{d}}\sim {\left({\epsilon}-{{\epsilon

    更新日期:2020-09-30
  • Evolution mechanism of principal modes in climate dynamics
    New J. Phys. (IF 3.539) Pub Date : 2020-09-29
    Yongwen Zhang, Jingfang Fan, Xiaoteng Li, Wenqi Liu and Xiaosong Chen

    Eigen analysis has been a powerful tool to distinguish multiple processes into different simple principal modes in complex systems. For a non-equilibrium system, the principal modes corresponding to the non-equilibrium processes are usually evolving with time. Here, we apply the eigen analysis into the complex climate systems. In particular, based on the daily surface air temperature in the tropics

    更新日期:2020-09-30
  • Abruptly autofocusing polycyclic tornado ring Airy beam
    New J. Phys. (IF 3.539) Pub Date : 2020-09-29
    You Wu, Chuangjie Xu, Zejia Lin, Huixin Qiu, Xinming Fu, Kaihui Chen and Dongmei Deng

    We introduce numerically a new polycyclic tornado ring Airy beam (PTRAB) induced by annular spiral zone phases with the second order chirped factor. The PTRAB has such properties of controllable multi focuses, the multi optical bottles and rotation. By choosing appropriate parameters, we can control the times of the multi autofocus and the autofocusing distance, the size and the number of the OBs,

    更新日期:2020-09-30
  • Quasi-nondegenerate pump–probe magnetooptical experiment in GaAs/AlGaAs heterostructure based on spectral filtration
    New J. Phys. (IF 3.539) Pub Date : 2020-09-29
    M Surýnek, L Nádvorník, E Schmoranzerová and P Němec

    We report on a quasi-nondegenerate pump–probe technique that is based on spectral-filtration of femtosecond laser pulses by a pair of mutually-spectrally-disjunctive commercially available interference filters. The described technique enables to obtain pump and probe pulses with wavelengths that are spectrally close but distinct. These contradictory requirements, which are dictated, for example, by

    更新日期:2020-09-30
  • Density functional theory studies of hydrogen bonding vibrations in sI gas hydrates
    New J. Phys. (IF 3.539) Pub Date : 2020-09-29
    Hao-Cheng Wang, Xu-Liang Zhu, Jing-Wen Cao, Xiao-Ling Qin, Ye-Chen Yang, Tian-Xiao Niu, Ying-Bo Lu and Peng Zhang

    To analyze the vibrational modes of water and methane in structure I gas hydrates, we constructed a 178-atom supercell with two small cages of type 5 12 and six large cages of type 5 12 6 2 . We applied the density functional theory method to simulate the vibrational spectrum and normal modes of methane hydrates. In accord with our previous studies, we confirmed that two groups of hydrogen bond (H-bond)

    更新日期:2020-09-30
  • Estimating the privacy of quantum-random numbers
    New J. Phys. (IF 3.539) Pub Date : 2020-09-27
    Johannes Seiler, Thomas Strohm and Wolfgang P Schleich

    We analyze the information an attacker can obtain on the numbers generated by a user by measurements on a subsystem of a system consisting of two entangled two-level systems. The attacker and the user make measurements on their respective subsystems, only. Already the knowledge of the density matrix of the subsystem of the user completely determines the upper bound on the information accessible to

    更新日期:2020-09-28
  • Quasiclassical approach to synergic synchrotron–Cherenkov radiation in polarized vacuum
    New J. Phys. (IF 3.539) Pub Date : 2020-09-27
    I I Artemenko, E N Nerush and I Yu Kostyukov

    Photon emission by an ultrarelativistic charged particle in extremely strong magnetic field is analyzed, with vacuum polarization and photon recoil taken into account. Vacuum polarization is treated phenomenologically via refractive index. The photon emission occurs in the synergic (cooperative) synchrotron–Cherenkov process [J Schwinger et al 1976 Annals of Physics 96 303] which is similar to the

    更新日期:2020-09-28
  • Hydrogenic entanglement
    New J. Phys. (IF 3.539) Pub Date : 2020-09-27
    Sofia Qvarfort, Sougato Bose and Alessio Serafini

    Is there any entanglement in the simplest ubiquitous bound system? We study the solutions to the time-independent Schrödinger equation for a hydrogenic system and devise two entanglement tests for free and localised states. For free hydrogenic systems, we compute the Schmidt basis diagonalisation for general energy eigenstates, and for a hydrogenic system localised to a three-dimensional Gaussian wavepacket

    更新日期:2020-09-28
  • An ultra-compact x-ray free-electron laser
    New J. Phys. (IF 3.539) Pub Date : 2020-09-27
    J B Rosenzweig, N Majernik, R R Robles, G Andonian, O Camacho, A Fukasawa, A Kogar, G Lawler, Jianwei Miao, P Musumeci, B Naranjo, Y Sakai, R Candler, B Pound, C Pellegrini, C Emma, A Halavanau, J Hastings, Z Li, M Nasr, S Tantawi, P. Anisimov, B Carlsten, F Krawczyk, E Simakov, L Faillace, M Ferrario, B Spataro, S Karkare, J Maxson, Y Ma, J Wurtele, A Murokh, A Zholents, A Cianchi, D Cocco and S B

    In the field of beam physics, two frontier topics have taken center stage due to their potential to enable new approaches to discovery in a wide swath of science. These areas are: advanced, high gradient acceleration techniques, and x-ray free electron lasers (XFELs). Further, there is intense interest in the marriage of these two fields, with the goal of producing a very compact XFEL. In this context

    更新日期:2020-09-28
  • Investigation of underwater quantum channels in a 30 meter flume tank using structured photons
    New J. Phys. (IF 3.539) Pub Date : 2020-09-21
    Felix Hufnagel, Alicia Sit, Frédéric Bouchard, Yingwen Zhang, Duncan England, Khabat Heshami, Benjamin J Sussman and Ebrahim Karimi

    Underwater quantum communication has recently been explored using polarization and orbital angular momentum (OAM). Here, we show that spatially structured modes, e.g., a coherent superposition of beams carrying both polarization and OAM, can also be used for underwater quantum cryptography. We also use the polarization degree of freedom to investigate the impact of the channel length on key rates for

    更新日期:2020-09-22
  • Entropy production at criticality in a nonequilibrium Potts model
    New J. Phys. (IF 3.539) Pub Date : 2020-09-21
    Thomas Martynec, Sabine H L Klapp and Sarah A M Loos

    Understanding nonequilibrium systems and the consequences of irreversibility for the system’s behavior as compared to the equilibrium case, is a fundamental question in statistical physics. Here, we investigate two types of nonequilibrium phase transitions, a second-order and an infinite-order phase transition, in a prototypical q -state vector Potts model which is driven out of equilibrium by coupling

    更新日期:2020-09-22
  • Experimental implementation of arbitrary entangled operations
    New J. Phys. (IF 3.539) Pub Date : 2020-09-21
    Seongjin Hong, Chang Hoon Park, Yeon-Ho Choi, Yong-Su Kim, Young-Wook Cho, Kyunghwan Oh and Hyang-Tag Lim

    Quantum entanglement lies at the heart of quantum mechanics in both fundamental and practical aspects. The entanglement of quantum states has been studied widely both theoretically and experimentally, however, the entanglement of operators has not been studied much experimentally in spite of its importance. Here, we propose a scheme to realize arbitrary entangled operations based on a coherent superposition

    更新日期:2020-09-22
  • On the effect of linear feedback and parametric pumping on a resonator’s frequency stability
    New J. Phys. (IF 3.539) Pub Date : 2020-09-21
    Zohreh Mohammadi, Toni L Heugel, James M L Miller, Dongsuk D Shin, Hyun-Keun Kwon, Thomas W Kenny, Ramasubramanian Chitra, Oded Zilberberg and Luis Guillermo Villanueva

    Resonant sensors based on micro- and nano-electro mechanical systems (M/NEMS) are ubiquitous in many sensing applications due to their outstanding performance capabilities, which are directly proportional to the quality factor ( Q ) of the devices. We address here a recurrent question in the field: do dynamical techniques that modify the effective Q (namely parametric pumping and direct drive velocity

    更新日期:2020-09-22
  • Testing generalised uncertainty principles through quantum noise
    New J. Phys. (IF 3.539) Pub Date : 2020-09-21
    Parth Girdhar and Andrew C Doherty

    Motivated by several approaches to quantum gravity, there is a considerable literature on generalised uncertainty principles particularly through modification of the canonical position–momentum commutation relations. Some of these modified relations are also consistent with general principles that may be supposed of any physical theory. Such modified commutators have significant observable consequences

    更新日期:2020-09-22
  • Macroscopic quantumness of optically conditioned mechanical systems
    New J. Phys. (IF 3.539) Pub Date : 2020-09-21
    Hannah McAleese and Mauro Paternostro

    We address the macroscopic quantumness of the state of mechanical systems subjected to conditional protocols devised for state engineering in cavity optomechanics. We use a measure of macroscopicity based on phase-space methods. We cover the transition regime into strong single-photon coupling, illustrating how measurements performed over the cavity field that drives the dynamics of a mechanical system

    更新日期:2020-09-22
  • Optimisation of diamond quantum processors
    New J. Phys. (IF 3.539) Pub Date : 2020-09-21
    YunHeng Chen, Sophie Stearn, Scott Vella, Andrew Horsley and Marcus W Doherty

    Diamond quantum processors consisting of a nitrogen-vacancy centre and surrounding nuclear spins have been the key to significant advancements in room-temperature quantum computing, quantum sensing and microscopy. The optimisation of these processors is crucial for the development of large-scale diamond quantum computers and the next generation of enhanced quantum sensors and microscopes. Here, we

    更新日期:2020-09-22
  • Sub-wavelength spin excitations in ultracold gases created by stimulated Raman transitions
    New J. Phys. (IF 3.539) Pub Date : 2020-09-21
    Yigal Ilin, Shai Tsesses, Guy Bartal and Yoav Sagi

    Raman transitions are used in quantum simulations with ultracold atoms for cooling, spectroscopy and creation of artificial gauge fields. Spatial shaping of the Raman fields allows local control of the effective Rabi frequency, which can be mapped to the atomic spin. Evanescent Raman fields are of special interest as they can provide a new degree of control emanating from their rapidly decaying profile

    更新日期:2020-09-22
  • Quantum device fine-tuning using unsupervised embedding learning
    New J. Phys. (IF 3.539) Pub Date : 2020-09-21
    N M van Esbroeck, D T Lennon, H Moon, V Nguyen, F Vigneau, L C Camenzind, L Yu, D M Zumbühl, G A D Briggs, D Sejdinovic and N Ares

    Quantum devices with a large number of gate electrodes allow for precise control of device parameters. This capability is hard to fully exploit due to the complex dependence of these parameters on applied gate voltages. We experimentally demonstrate an algorithm capable of fine-tuning several device parameters at once. The algorithm acquires a measurement and assigns it a score using a variational

    更新日期:2020-09-22
  • Spatial localization and pattern formation in discrete optomechanical cavities and arrays
    New J. Phys. (IF 3.539) Pub Date : 2020-09-21
    J Ruiz-Rivas, G Patera, C Navarrete-Benlloch, E Roldán and G J de Valcárcel

    We investigate theoretically the generation of nonlinear dissipative structures in optomechanical (OM) systems containing discrete arrays of mechanical resonators. We consider both hybrid models in which the optical system is a continuous multimode field, as it would happen in an OM cavity containing an array of micro-mirrors, and also fully discrete models in which each mechanical resonator interacts

    更新日期:2020-09-22
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