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phase coherence

Stefan Stevanovic, Boris Pervan
We propose a novel GPS phase-lock loop (PLL) performance metric based on the standard deviation of tracking error (defined as the discriminator's estimate of the true phase error), and explain its advantages over the popular phase jitter metric using theory, numerical simulation, and experimental results. We derive an augmented GPS phase-lock loop (PLL) linear model, which includes the effect of coherent averaging, to be used in conjunction with this proposed metric. The augmented linear model allows more accurate calculation of tracking error standard deviation in the presence of additive white Gaussian noise (AWGN) as compared to traditional linear models...
January 19, 2018: Sensors
Federico Carollo, Juan P Garrahan, Igor Lesanovsky, Carlos Pérez-Espigares
We consider a class of either fermionic or bosonic noninteracting open quantum chains driven by dissipative interactions at the boundaries and study the interplay of coherent transport and dissipative processes, such as bulk dephasing and diffusion. Starting from the microscopic formulation, we show that the dynamics on large scales can be described in terms of fluctuating hydrodynamics. This is an important simplification as it allows us to apply the methods of macroscopic fluctuation theory to compute the large deviation (LD) statistics of time-integrated currents...
November 2017: Physical Review. E
Sajal Kumar Giri, Himangshu Prabal Goswami
By periodically driving the temperature of reservoirs in a quantum heat engine, geometric or Pancharatnam-Berry phaselike (PBp) effects in the thermodynamics can be observed. The PBp can be identified from a generating function (GF) method within an adiabatic quantum Markovian master equation formalism. The GF is shown not to lead to a standard open quantum system's fluctuation theorem in the presence of phase-different modulations with an inapplicability in the use of large deviation theory. Effect of quantum coherences in optimizing the flux is nullified due to PBp contributions...
November 2017: Physical Review. E
Gabriela Petrungaro, Koichiro Uriu, Luis G Morelli
We study the dynamics of mobile, locally coupled identical oscillators in the presence of coupling delays. We find different kinds of chimera states in which coherent in-phase and antiphase domains coexist with incoherent domains. These chimera states are dynamic and can persist for long times for intermediate mobility values. We discuss the mechanisms leading to the formation of these chimera states in different mobility regimes. This finding could be relevant for natural and technological systems composed of mobile communicating agents...
December 2017: Physical Review. E
Natalia Vladimirova
Here we study how coherence appears in a system driven by noise at small scales. In the wave turbulence modeled by the Gross-Pitaevskii or the nonlinear Schrödinger equation, we observe states with correlation scales smaller than the system size but much larger than the excitation scale. We call a such state precondensate to distinguish it from condensate defined as a systemwide coherent state. Both condensate and precondensate are characterized by large-scale phase coherence and a narrow distribution of amplitudes...
December 2017: Physical Review. E
Ali Ü C Hardal, Nur Aslan, C M Wilson, Özgür E Müstecaplıoğlu
We propose a quantum heat engine composed of two superconducting transmission line resonators interacting with each other via an optomechanical-like coupling. One resonator is periodically excited by a thermal pump. The incoherently driven resonator induces coherent oscillations in the other one due to the coupling. A limit cycle, indicating finite power output, emerges in the thermodynamical phase space. The system implements an all-electrical analog of a photonic piston. Instead of mechanical motion, the power output is obtained as a coherent electrical charging in our case...
December 2017: Physical Review. E
Alexey A Koronovskii, Maria K Kurovskaya, Olga I Moskalenko, Alexander Hramov, Stefano Boccaletti
We report that explosive synchronization of networked oscillators (a process through which the transition to coherence occurs without intermediate stages but is rather characterized by a sudden and abrupt jump from the network's asynchronous to synchronous motion) is related to self-similarity of synchronous clusters of different size. Self-similarity is revealed by destructing the network synchronous state during the backward transition and observed with the decrease of the coupling strength between the nodes of the network...
December 2017: Physical Review. E
J Shena, J Hizanidis, P Hövel, G P Tsironis
The dynamics of a large array of coupled semiconductor lasers is studied numerically for a nonlocal coupling scheme. Our focus is on chimera states, a self-organized spatiotemporal pattern of coexisting coherence and incoherence. In laser systems, such states have been previously found for global and nearest-neighbor coupling, mainly in small networks. The technological advantage of large arrays has motivated us to study a system of 200 nonlocally coupled lasers with respect to the emerging collective dynamics...
September 2017: Physical Review. E
Megan O Hill, Irene Calvo-Almazan, Mark Allain, Martin Holt, Andrew Ulvestad, Julian Treu, Gregor Koblmueller, Chunyi Huang, Xiaojing Huang, Hanfei Yan, E Nazarestski, Yong S Chu, G Brian Stephenson, Virginie Chamard, Lincoln Lauhon, Stephan O Hruszkewycz
III-As nanowires are candidates for near infrared light emitters and detectors that can be directly integrated onto silicon. However, nanoscale to microscale variations in structure, composition, and strain within a given nanowire, as well as variations between nanowires, pose challenges to correlating microstructure with device performance. In this work, we utilize coherent nano-focused x-rays to characterize stacking defects and strain in a single InGaAs nanowire supported on Si. By reconstructing diffraction patterns from the 2-1-10 Bragg peak, we show that the lattice orientation varies along the length of the wire, while the strain field along the cross-section is largely unaffected, leaving the band structure unperturbed...
January 18, 2018: Nano Letters
Paola Palladino, Caterina Artuso
In the present study, we aimed to examine how specific objects are updated in working memory. We compared conditions in which contents or content-context bindings from working memory were both encoded and updated (Experiment 1). In addition, for bindings, we manipulated the memory load (i.e., number of contents) to maintain during updating. Results indicated that memory load did not specifically affect the process; rather, the content-context binding (vs. single contents) was critical in determining the increase in response latencies...
January 18, 2018: Journal of General Psychology
Orit Markowitz, Katie Wang, Amanda Levine, Michelle Schwartz, Sumeet Minhas, Eleanor Feldman, Daniel M Siegel
OBJECTIVE: To determine whether actinic keratosis and photodamaged perilesional areas (field cancerization) treated successfully with topical ingenol mebutate gel 0.015% remained clear one year later, and to treat actinic keratosis and perilesional skin not treated one year earlier. DESIGN: Single-center, single-arm, open-label extension of an original clinical study completed one year earlier. SETTING: An outpatient clinic. PARTICIPANTS: Fifteen of the original 28 study patients enrolled in and who completed the extension phase...
October 2017: Journal of Clinical and Aesthetic Dermatology
K Ohmi, N Kuroo, K Oide, D Zhou, F Zimmermann
In recent years the "crab-waist collision" scheme [P. Raimondi, Proceedings of 2nd SuperB Workshop, Frascati, 2006.; M. Zobov et al., Phys. Rev. Lett. 104, 174801 (2010)PRLTAO0031-900710.1103/PhysRevLett.104.174801] has become popular for circular e^{+} e^{-} colliders. The designs of several future colliders are based on this scheme. So far the beam-beam effects for collisions under a large crossing angle with or without crab waist were mostly studied using weak-strong simulations. We present here strong-strong simulations showing a novel strong coherent head-tail instability, which can limit the performance of proposed future colliders...
September 29, 2017: Physical Review Letters
Pietro Liuzzo-Scorpo, Andrea Mari, Vittorio Giovannetti, Gerardo Adesso
Given a certain amount of entanglement available as a resource, what is the most efficient way to accomplish a quantum task? We address this question in the relevant case of continuous variable quantum teleportation protocols implemented using two-mode Gaussian states with a limited degree of entanglement and energy. We first characterize the class of single-mode phase-insensitive Gaussian channels that can be simulated via a Braunstein-Kimble protocol with nonunit gain and minimum shared entanglement, showing that infinite energy is not necessary apart from the special case of the quantum limited attenuator...
September 22, 2017: Physical Review Letters
I-D Potirniche, A C Potter, M Schleier-Smith, A Vishwanath, N Y Yao
We propose and analyze two distinct routes toward realizing interacting symmetry-protected topological (SPT) phases via periodic driving. First, we demonstrate that a driven transverse-field Ising model can be used to engineer complex interactions which enable the emulation of an equilibrium SPT phase. This phase remains stable only within a parametric time scale controlled by the driving frequency, beyond which its topological features break down. To overcome this issue, we consider an alternate route based upon realizing an intrinsically Floquet SPT phase that does not have any equilibrium analog...
September 22, 2017: Physical Review Letters
Nils Raabe, Tianli Feng, Tobias Witting, Ayhan Demircan, Carsten Brée, Günter Steinmeyer
The concept of coherence is of fundamental importance for describing the physical characteristics of light and for evaluating the suitability for experimental application. In the case of pulsed laser sources, the pulse-to-pulse coherence is usually considered for a judgment of the compressibility of the pulse train. This type of coherence is often lost during propagation through a highly nonlinear medium, and pulses prove incompressible despite multioctave spectral coverage. Notwithstanding the apparent loss of interpulse coherence, however, supercontinua enable applications in precision frequency metrology that rely on coherence between different spectral components within a laser pulse...
September 22, 2017: Physical Review Letters
Sebastian Maehrlein, Alexander Paarmann, Martin Wolf, Tobias Kampfrath
In stimulated Raman scattering, two incident optical waves induce a force oscillating at the difference of the two light frequencies. This process has enabled important applications such as the excitation and coherent control of phonons and magnons by femtosecond laser pulses. Here, we experimentally and theoretically demonstrate the so far neglected up-conversion counterpart of this process: THz sum-frequency excitation of a Raman-active phonon mode, which is tantamount to two-photon absorption by an optical transition between two adjacent vibrational levels...
September 22, 2017: Physical Review Letters
Nyeonju Kang, James H Cauraugh
Neural coupling across hemispheres and homologous muscles often appears during bimanual motor control. Force coupling in a specific frequency domain may indicate specific bimanual force coordination patterns. This study investigated coherence on pairs of bimanual isometric index finger force while manipulating visual gain and task asymmetry conditions. We used two visual gain conditions (low and high gain = 8 and 512 pixels/N), and created task asymmetry by manipulating coefficient ratios imposed on the left and right index finger forces (0...
January 11, 2018: Neuroscience Letters
Surajit Kayal, Khokan Roy, Siva Umapathy
Ultrafast torsional dynamics plays an important role in the photoinduced excited state dynamics. Tetraphenylethylene (TPE), a model system for the molecular motor, executes interesting torsional dynamics upon photoexcitation. The photoreaction of TPE involves ultrafast internal conversion via a nearly planar intermediate state (relaxed state) that further leads to a twisted zwitterionic state. Here, we report the photoinduced structural dynamics of excited TPE during the course of photoisomerization in the condensed phase by ultrafast Raman loss (URLS) and femtosecond transient absorption (TA) spectroscopy...
January 14, 2018: Journal of Chemical Physics
Jan W van der Scheer, Yoshi-Ichiro Kamijo, Christof A Leicht, Philip J Millar, Manabu Shibasaki, Victoria L Goosey-Tolfrey, Fumihiro Tajima
STUDY DESIGN: Experimental study. OBJECTIVES: To characterize static and dynamic cerebral autoregulation (CA) of individuals with cervical spinal cord injury (SCI) compared to able-bodied controls in response to moderate increases in mean arterial pressure (MAP) caused by mild whole-body cold stress. SETTING: Japan METHODS: Five men with complete autonomic cervical SCI (sustained > 5 y) and six age-matched able-bodied men participated in hemodynamic, temperature, catecholamine and respiratory measurements for 60 min during three consecutive stages: baseline (10 min; 33 °C water through a thin-tubed whole-body suit), mild cold stress (20 min; 25 °C water), and post-cold recovery (30 min; 33 °C water)...
January 12, 2018: Spinal Cord
Yael Oran, Izhar Bar-Gad
Fast spiking interneurons (FSIs) exert powerful inhibitory control over the striatum and are hypothesized to balance the massive excitatory cortical and thalamic input to this structure. We recorded neuronal activity in the dorsolateral striatum and globus pallidus (GP) concurrently with the detailed movement kinematics of freely behaving female rats prior to and following selective inhibition of FSI activity using IEM-1460 microinjections. The inhibition led to the appearance of episodic rest tremor in the body part that depended on the somatotopic location of the injection within the striatum...
January 12, 2018: Journal of Neuroscience: the Official Journal of the Society for Neuroscience
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