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Transient chaos is very common in periodically forced dynamical systems, but transient strange nonchaotic dynamics have not been studied by researchers. Therefore, it is meaningful to explore the dynamical phenomena of transient chaos and transient strange nonchaos. In this paper, we investigate a quasiperiodically forced cantilever beam system with impacts and discover abundant transient dynamic phenomena. Firstly, we determine the transient interval by the bifurcation diagram and the maximum Lyapunov exponent and investigate the correspondence between them. Secondly, we identify transient chaos and transient strange nonchaos and distinguish transient attractors and permanent attractors using the maximum Lyapunov exponent. Furthermore, we verify the strange property of attractors through the phase sensitivity and the power spectrum. [ABSTRACT FROM AUTHOR]

For the purpose of detecting waterborne bacteria, a high-phase-sensitivity SPR sensor with an Ag–TiO2–Franckeite–WS2 hybrid structure is designed using an improved seeker optimization algorithm (ISOA). By optimizing each layer of sensor construction simultaneously, the ISOA guarantees a minimum reflectance of less than 0.01 by Ag (20.36 nm)–TiO2 (6.08 nm)–Franckeite (monolayer)–WS2 (bilayer) after 30 iterations for E. coli. And the optimal phase sensitivity is 2.378 × 106 deg/RIU. Sensor performance and computing efficiency have been greatly enhanced using the ISOA in comparison to the traditional layer-by-layer technique and the SOA method. This will enable sensors to detect a wider range of bacteria with more efficacy. As a result, the ISOA-based design idea could provide SPR biosensors with new applications in environmental monitoring. [ABSTRACT FROM AUTHOR]

We have theoretically investigated the phase sensitivity of the hybrid interferometer with two coherent beams using the method of balance homodyne detection. The measurement device is a nonlinear–linear hybrid interferometer consisting of an optical parametric amplifier and a beam splitter. We prove that the phase sensitivity can beat the shot noise limit in the optimal conditions. Furthermore, we derive the quantum Cramér–Rao bound of the hybrid interferometer. The effects of transmission loss and detection loss on the measurement accuracy are discussed. The detection accuracy of this scheme is compared with that of the conventional SU (1,1) interferometer. Our results show that this scheme outperforms the conventional SU (1,1) interferometer scheme at high parametric strength. This scheme can be implemented with existing experimental techniques and will have important applications in quantum precision measurements. [ABSTRACT FROM AUTHOR]

A differential evolution particle swarm optimization (DEPSO) is presented for the design of a high-phase-sensitivity surface plasmon resonance (SPR) gas sensor. The gas sensor is based on a bilayer metal film with a hybrid structure of blue phosphorene (BlueP)/transition metal dichalcogenides (TMDCs) and MXene. Initially, a Ag-BlueP/TMDCs-Ag-MXene heterostructure is designed, and its performance is compared with that of the conventional layer-by-layer method and particle swarm optimization (PSO). The results indicate that optimizing the thickness of the layers in the gas sensor promotes phase sensitivity. Specifically, the phase sensitivity of the DEPSO is significantly higher than that of the PSO and the conventional method, while maintaining a lower reflectivity. The maximum phase sensitivity achieved is 1.866 × 106 deg/RIU with three layers of BlueP/WS2 and a monolayer of MXene. The distribution of the electric field is also illustrated, demonstrating that the optimized configuration allows for better detection of various gases. Due to its highly sensitive characteristics, the proposed design method based on the DEPSO can be applied to SPR gas sensors for environmental monitoring. [ABSTRACT FROM AUTHOR]

Attention can be selectively tuned to particular features at different spatial locations or objects. The deployment of attention can be guided by properties, such as color, orientation, and so forth, as guiding features. What might be such guiding features for visual stimuli under dynamic rhythmic conditions? We asked specifically what might be the parameters that attract attention when perceiving a visual rhythm. We used a visual search paradigm, in which a dynamic search display consisted of vertically "bouncing balls" with regular rhythms. The search target was defined by a unique visual rhythm (i.e., with either a shorter or longer period) among rhythmic distractors sharing an identical period. We modulated amplitudes and phases of the distractor balls systematically. The results showed a crucial factor of the phase, not the amplitude. If the phase is violated, the target suddenly "pops out" as an "oddball," showing an efficient parallel search. The findings indicate in general the essential role of the phase in conjunction with amplitude and period for visual rhythm perception. Furthermore, a higher saliency of moving objects with a higher frequency component has also been disclosed. [ABSTRACT FROM AUTHOR]

In this paper, we study strange nonchaotic attractors (SNAs) and multistable dynamics in a class of nonlinear economic systems. For quasiperiodically forced case, the generation and evolution mechanisms of SNAs are discussed. The fractal, Heagy–Hammel, torus doubling, and intermittency routes to SNAs are identified. The Lyapunov exponent, phase-sensitive function and power spectrum are used to characterize the dynamical and geometrical properties of SNAs. Moreover, when multistable phenomenon occur in the system, the boundaries of the basin of attraction may become intertwined, which leads to the economic unpredictability in the long run. [ABSTRACT FROM AUTHOR]

We study the improvement in the phase sensitivity of a Mach–Zehnder interferometer (MZI) using the superposition of 'Schrödinger's cat-like state with the vacuum state (SCVS)' and the vacuum state as inputs. With this setup, we examine the effect on the phase sensitivity of the interferometer using a parity detection scheme. We find better phase sensitivity under some conditions for this setup having potential application in quantum sensing. [ABSTRACT FROM AUTHOR]

We have conducted a study on a very-low-frequency acoustic-velocity sensor which is based on a cantilever of distributed-feedback (DFB) fiber laser immersed in castor oil. A mathematical model of the frequency dependent response of the proposed sensor to the acoustic pressure signal influenced by the fluid viscosity is established. We have fabricated the proposed sensor and conducted experimental measurements in the standing wave tube. The results show that the sensor has an average phase sensitivity of −179.5 dB (0 dB = 1 rad/μPa) with ±1.45 dB fluctuation over the frequency range of 20–38 Hz. It has good cosine directivity with a directivity index of 32.5 dB and axial maximum asymmetry of 0.4 dB. The sensor presents promising applications for detecting very-low-frequency underwater acoustic signals. [ABSTRACT FROM AUTHOR]

We attempt to demonstrate optical phase switches in a typical light storage experiment. We computed propagation dynamics of light pulses in sodium-23, rubidium-87, and potassium-39 vapors. These vapors have the same tensorial sets of the density matrix with a nuclear spin I = 3/2. The energy scheme is known as the double-Λ system. We considered an excitation mechanism in which one of two Λ systems was excited by two-color pulses, probe, and drive, following the standard electromagnetically induced transparency configuration. The probe channel contains delayed two pulses after the first probe pulse. Gain is generated through the drive channel and is exposed during propagation. We further investigated the spatiotemporal phase variations in the pulses and found discrete phase distribution for different vapors. The spatiotemporal evolution of the irreducible tensorial sets defines structural differential equations. Additionally, it is particularly suitable for parallel processing. We hope our study finds an application in comparison to alkali vapor magnetometry. [ABSTRACT FROM AUTHOR]

An optical refractive index sensor with a metal-multilayer dielectric film structure based on Fano resonance (FR) is proposed to solve the low sensitivity of traditional surface plasmon resonance (SPR) sensors. The sensor’s performance can be optimized, and a plasmon-induced reflection (PIR) of incident light can also be achieved by adjusting the thickness of each layer. Through an innovative experimental design, the practical measurement phase sensitivity of the sensor based on FR is achieved for the first time, which provides a reference for subsequent theoretical research and experimental preparation. The wavelength sensitivity and the phase sensitivity can reach 345 nm/RIU and $4.00\times 10^{{5}\circ }$ /RIU, which experimentally proves that phase interrogation has higher sensitivity than traditional wavelength interrogation. The sensor can be a promising candidate for exploiting novel plasmonic sensors with ultrahigh sensitivity and resolution for biosensing applications. [ABSTRACT FROM AUTHOR]

The phase image of tapping‐mode atomic force microscopy (TM‐AFM) contains energy dissipation, which is related to the sample information on the physical properties such as the sample Young's modulus, adhesion, surface morphology and subsurface morphology. When TM‐AFM is used for sample measurement, the frequency near the first resonance peak of probe is usually selected to drive the probe vibration. When the probe vibration is driven by the frequency, the probe has a high amplitude sensitivity, but the phase sensitivity is relatively low. In this paper, the frequency at the probe phase resonance peak was selected for driving the probe vibration to measure the sample, which improved the image resolution. Phase imaging was performed on three uniform photoresist samples with different thicknesses and the same structure. When the scanning parameters were fixed and the probe setpoint value was changed alone, it was found that with the decrease of setpoint value the horizontal resolution of the phase subsurface image was decreased, and the depth sensitivity was increased first and then decreased. The result shows that TM‐AFM working at the phase resonance peak can better realise the subsurface imaging of samples at different depths. Phase subsurface imaging at the resonance can be used to quantitatively obtain subsurface phase images of different depths. [ABSTRACT FROM AUTHOR]

The phase sensitivity of the condenser type acoustic transducers at low frequencies is crucial for locating large-scale natural and manmade activities, but is now commonly calibrated based on comparison methods. Although the primary method, which traces its sensitivity back to the international standard unit is few studied. Recently, the explicit sensitivity models of the condenser type acoustic transducers based on the laser-pistonphone technique are built, and can be used to study the phase responses of acoustic transducers at infrasonic frequencies. So that, in this paper, the phase sensitivities of acoustic transducers when its rear vent connected to the calibrating sound field or outside atmosphere are studied in detail. Secondly, time domain analysis of generated sound pressures by displacement excitation are derived to reveal the mechanism of phase variation. Calculations show two distinct sensitivities with 90° phase lead and −10° phase lag limits for vent in field and vent out field calibrations, which are dominated by the pressure leakage and heat conduction effects at infrasonic frequencies. [ABSTRACT FROM AUTHOR]

The basins of attraction of periodic orbits or focus equilibria of a given vector field are foliated by forward-time isochrons, defined as all initial conditions that synchronize under the flow with a given phase. Similarly, backward-time isochrons of repelling periodic orbits or focus equilibria foliate their respective basins of repulsion. We present a case study of a planar system that features a sequence of bifurcations, including a saddle-node bifurcation of periodic orbits, a homoclinic bifurcation and Hopf bifurcations, that change the nature and existence of periodic orbits. We explain how the basins and isochron foliations change throughout the sequence of bifurcations. In particular, we identify structurally stable tangencies between the foliations by forward-time and backward-time isochrons, which are curves in the plane, in regions of phase space where they exist simultaneously. Such tangencies are generically quadratic and associated with sharp turns of isochrons and phase sensitivity of the system. In contrast to the earlier reported cubic isochron foliation tangency (CIFT) mechanism, which generates a pair of tangency orbits, we find isochron foliation tangencies that occur along single specific orbits in the respective basin of attraction or repulsion. Moreover, the foliation tangencies we report arise from actual bifurcations of the system, while a CIFT is not associated with a topological change of the underlying phase portrait. The properties and interactions of isochron foliations are determined and illustrated by computing a representative number of forward-time and backward-time isochrons as arclength-parametrized curves with a boundary value problem set-up. Our algorithm for computing isochrons has been further refined and implemented in the Matlab package CoCo; it is made available as Matlab code in the supplementary material of this paper, together with a guide that walks the user through the computation of two specific isochron foliations. [ABSTRACT FROM AUTHOR]

Low frequency primary calibrations of condenser microphones are the basis of accurate measurement of low frequency sound and infrasound. Prior arts on the primary phase calibrations differ greatly, simultaneous primary amplitude and phase calibrations are rarely seen. Recently, two infrasonic sensitivity models of condenser microphones based on the pistonphone technique, for the vent immersed in sound field and outside are derived. The relevant models can explicitly characterize the influence of pistonphone, microphone and environment on the voltage output and sensitivity of the microphone. On this basis, simultaneous primary amplitude and phase calibration tests are evaluable. Based on adequate performance tests of the designed laser pistonphone, this paper carries out in-depth primary microphone calibrations. The calibrated infrasonic amplitude and phase sensitivities are in good agreement with theoretical results, thus proves their values to reveal and quantify the influence of various factors on the calibration results based on the pistonphone technique. [ABSTRACT FROM AUTHOR]

Multimode integrated interferometers have great potential for both spectral engineering and metrological applications. However, the material dispersion of integrated platforms constitutes an obstacle that limits the performance and precision of such interferometers. At the same time, two-colour nonlinear interferometers present an important tool for metrological applications, when measurements in a certain frequency range are difficult. In this manuscript, we theoretically developed and investigated an integrated multimode two-colour SU(1,1) interferometer operating in a supersensitive mode. By ensuring the proper design of the integrated platform, we suppressed the dispersion, thereby significantly increasing the visibility of the interference pattern. The use of a continuous wave pump laser provided the symmetry between the spectral shapes of the signal and idler photons concerning half the pump frequency, despite different photon colours. We demonstrate that such an interferometer overcomes the classical phase sensitivity limit for wide parametric gain ranges, when up to 3 × 10 4 photons are generated. [ABSTRACT FROM AUTHOR]

In this study, we propose an improved theoretical model for the phase estimation scheme with inverse operations and compare it with the conventional phase estimation model in terms of the Fisher information and error propagation equation. In addition, we analyse the phase sensitivity of Mach-Zehnder Interferometer (MZI) and SU(1,1) interferometer (SU(1,1)I) with the coherent or squeezed states as input for intensity detection. We also discuss the phase sensitivity of MZI and SU(1,1)I with inverse displaced and inverse squeezed operations for intensity detection, and extensively compare them with and without the inverse operation scheme. Accordingly, we conclude that the phase sensitivity of interferometers can be significantly enhanced by embedding additional inverse operations. [ABSTRACT FROM AUTHOR]

We theoretically analyze the phase sensitivity of an SU (1 , 1) interferometer with various input states by product detection in this paper. This interferometer consists of two parametric amplifiers that play the role of beam splitters in a traditional Mach–Zehnder interferometer. The product of the amplitude quadrature of one output mode and the momentum quadrature of the other output mode is measured via balanced homodyne detection. We show that product detection has the same phase sensitivity as parity detection for most cases, and it is even better in the case with two coherent states at the input ports. The phase sensitivity is also compared with the Heisenberg limit and the quantum Cramér–Rao bound of the SU (1 , 1) interferometer. This detection scheme can be easily implemented with current homodyne technology, which makes it highly feasible. It can be widely applied in the field of quantum metrology. [ABSTRACT FROM AUTHOR]

The design, development, fabrication, and testing of a wideband reflectarray antenna with a novel concentric ring element operating over Ku/K band frequencies is presented in this paper. The element characterization is performed using the infinite array approach and is inferred that the proposed unit cell offers a higher phase variation of 643° by changing the size of the concentric rings. The proposed reflectarray antenna has a circular geometry and is constructed using 437 elements with an element separation of 0.43λ0. The proposed reflectarray offers a 3 dB gain bandwidth of 35% (15–21 GHz). The aperture efficiency is estimated to be 58.78% at 16.5 GHz. The prototype reflectarray is fabricated and tested to validate the simulation results. The measured peak gain of the reflectarray is 28.4 dBi with a side lobe level of −17.6 dB. The measured cross‐polarization level is less than −32 dB. Furthermore, it is inferred that the proposed unit cell has a reduced maximum phase sensitivity of 246°/mm with a gain selectivity of 6 dB at the lowest operating frequency. The proposed broadband reflectarray with enhanced performance characteristics is suitable for application in satellite communication and aeronautical radio navigation. [ABSTRACT FROM AUTHOR]

Magnetoelastic sensors for the detection of low-frequency and low-amplitude magnetic fields are in the focus of research for more than 30 years. In order to minimize the limit of detection (LOD) of such sensor systems, it is of high importance to understand and to be able to quantify the relevant noise sources. In this contribution, cantilever-type electromechanical and magnetoelastic resonators, respectively, are comprehensively investigated and mathematically described not only with regard to their phase sensitivity but especially to the extent of the sensor-intrinsic phase noise. Both measurements and calculations reveal that the fundamental LOD is limited by additive phase noise due to thermal-mechanical noise of the resonator, i.e. by thermally induced random vibrations of the cantilever, and by thermal-electrical noise of the piezoelectric material. However, due to losses in the magnetic material parametric flicker phase noise arises, limiting the overall performance. In particular, it is shown that the LOD is virtually independent of the magnetic sensitivity but is solely determined by the magnetic losses. Instead of the sensitivity, the magnetic losses, represented by the material’s effective complex permeability, should be considered as the most important parameter for the further improvement of such sensors in the future. This implication is not only valid for magnetoelastic cantilevers but also applies to any type of magnetoelastic resonator. [2020-0219] [ABSTRACT FROM AUTHOR]

This work elucidates the numerical simulations carried out for the performance analysis of surface plasmon resonance (SPR)–based fiber-optic sensors using thin layers of tantalum (v) oxide (Ta2O5) and graphene in phase interrogation scheme. For this purpose, fiber-optic sensing probes with three distinct configurations have been used which include consecutive as well as individual layers of Ta2O5 and graphene over silver-coated unclad core of a silica optical fiber. The performance of sensing probes is studied in terms of the phase difference arising between TM and TE polarized components of the incident light as they propagate through the sensing region, besides their SPR responses towards varying refractive index of analyte layer, making use of the transfer matrix theory for stratified isotropic optical media in conjunction with geometrical optics. Theoretical investigations reveal that the probe having multi-layered arrangement of Ta2O5 and graphene possesses maximum sensitivity of propagating phase difference with magnitude 4.852 × 105 Deg/RIU at analyte refractive index of 1.33 in comparison to probes with individual Ta2O5 (3.731 × 105 Deg/RIU) and graphene (0.362 × 105 Deg/RIU) layers. Moreover, the design parameters of the probes have been numerically maneuvered with an aim of achieving an analyte refractive index of 1.33 in transmitted light spectrum to display the feasibility of proposed sensor in biochemical fields. The reported results unfold an innovative perspective to widen the application horizon of fiber-optic SPR sensors in phase interrogation scheme. [ABSTRACT FROM AUTHOR]

Surface plasmon resonance (SPR) biosensor is widely used for its high precision and real-time analysis. In this paper, SPR biosensor based on the hybrid structure of metal–indium tin oxide (ITO)–WS2 are proposed and investigated. By optimizing the thickness of metals (Au, Cu, Ag), ITO and WS2, the reflectivity of 2.932 × 10−7 a.u and highest phase sensitivity of 1.711 × 106 deg/RIU are obtained by using Ag–ITO–WS2-dielectric structure. Compared with the traditional metal-based SPR sensor, the performance of the proposed one is improved up to ~ 25.8 times. The results show that ITO and WS2 have an important effect on enhancing SPR sensing performance. [ABSTRACT FROM AUTHOR]

In this paper, a surface plasmon resonance (SPR) sensor based on the hybrid structure of silver (Ag)-indium tin oxide (ITO)-graphene is proposed and investigated. SPR biosensors are subdivided into three kinds of structures Ag, Ag-graphene, and Ag-ITO-graphene, when carried out using their respective optimized structure parameters. According to our analysis and comparison, the ITO-assisted SPR biosensor has an optimal reflectivity of 3.587 × 10−8 and a maximum phase sensitivity of 1.707 × 106°/RIU, which shows that ITO can be employed to further enhance the SPR sensing performance even with the existence of graphene. [ABSTRACT FROM AUTHOR]

Improving the phase sensitivity of the optical fiber Sagnac sensor is very important for accurately detecting weak signals of acoustic emission. Theoretical analysis shows that the initial phase of the sensor is π under ideal conditions, and the maximum phase sensitivity is obtained when the bias phase is π/2. In this work, an experimental system was built with an aluminum alloy plate as the experimental object. The initial phase of the sensor was modulated by a Y-branch waveguide, and the fitting curve of the experimental data was in good agreement with the curve of the numerical simulation. Moreover, our experiments show there was a single value for the bias phase of π/2, which significantly deviated from the theoretical value. The results show that the greatest phase sensitivity of the sensor not only could be increased by nearly nine times through modulating the initial phase, but also could suppress the harmonic interferences in the sensing system. This study can provide a useful reference for improving the phase sensitivity of the optical fiber Sagnac AE sensor in practical applications. [ABSTRACT FROM AUTHOR]

In rodents, the progression of extrastriate areas located laterally to primary visual cortex (VI) has been assigned to a putative objectprocessing pathway (homologous to the primate ventral stream), based on anatomical considerations. Recently, we found functional support for such attribution (Tafazoli et al., 2017), by showing that this cortical progression is specialized for coding object identity despite view changes, the hallmark property of a ventral-like pathway. Here, we sought to clarify what computations are at the base of such specialization. To this aim, we performed multielectrode recordings from VI and laterolateral area LL (at the apex of the putative ventral-like hierarchy) of male adult rats, during the presentation of drifting gratings and noise movies. We found that the extent to which neuronal responses were entrained to the phase of the gratings sharply dropped from VI to LL, along with the quality of the receptive fields inferred through reverse correlation. Concomitantly, the tendency of neurons to respond to different oriented gratings increased, whereas the sharpness of orientation tuning declined. Critically, these trends are consistent with the nonlinear summation of visual inputs that is expected to take place along the ventral stream, according to the predictions of hierarchical models of ventral computations and a meta-analysis of the monkey literature. This suggests an intriguing homology between the mechanisms responsible for building up shape selectivity and transformation tolerance in the visual cortex of primates and rodents, reasserting the potential of the latter as models to investigate ventral stream functions at the circuitry level. [ABSTRACT FROM AUTHOR]

Purpose: Acquisition of high‐resolution imaging data using multiple excitations without the sensitivity to fluctuations of the transverse magnetization phase, which is a major problem of multi‐shot MRI. Theory and Methods: The concept of superresolution MRI based on microscopic tagging is analyzed using an analogy with the optical method of structured illumination. Sinusoidal tagging is shown to provide subpixel resolution by mixing of neighboring spatial frequency (k‐space) bands. It represents a phaseless modulation added on top of the standard Fourier encoding, which allows the phase fluctuations to be discarded at an intermediate reconstruction step. Improvements are proposed to correct for tag distortions due to magnetic field inhomogeneity and to avoid the propagation of Gibbs ringing from intermediate low‐resolution images to the final image. The method was applied to diffusion‐weighted EPI. Results: Artifact‐free superresolution images can be obtained despite a finite duration of the tagging sequence and related pattern distortions by a field map based phase correction of band‐wise reconstructed images. The ringing effect present in the intermediate images can be suppressed by partial overlapping of the mixed k‐space bands in combination with an adapted filter. High‐resolution diffusion‐weighted images of the human head were obtained with a three‐shot EPI sequence despite motion‐related phase fluctuations between the shots. Conclusion: Due to its phaseless character, tagging‐based sub‐pixel encoding is an alternative to k‐space segmenting in the presence of unknown phase fluctuations, in particular those due to motion under strong diffusion gradients. Proposed improvements render the method practicable in realistic conditions. [ABSTRACT FROM AUTHOR]

Laue microdiffraction is used to determine the full elastic strain tensor of the γ and γ′ phases in grains of a nickel-based superalloy with a coarse-grained microstructure. A `rainbow' filter and an energy dispersive point detector are employed to measure the energy of Bragg reflections. For the two techniques, an uncertainty of ±2.5 × 10−3 Å is obtained for the undetermined crystal lattice parameter. Our measurements show that the filter method provides better confidence, energy resolution, accuracy and acquisition time. The sensitivity of each method with respect to the γ-γ′ lattice mismatch is demonstrated with measurements in samples with average precipitate sizes of 200 and 2000 nm. For the 200 nm precipitate size, the lattice mismatch is less than 2 × 10−3 Å and the dilatational strains are close to ±1.5 × 10−3 depending on the considered phase. For the 2000 nm precipitate size, the lattice mismatch is close to 8 × 10−3 Å and almost no elastic strain occurs in the microstructure. [ABSTRACT FROM AUTHOR]

Purpose Fourier encoded MRI signal is complex and, therefore, sensitive to uncontrolled phase variations caused, e.g., by object motion. An alternative encoding is proposed which leads to phaseless (positive real) signals and allows the phase fluctuations to be removed by simple magnitude calculation before the Fourier transform. Theory and Methods Phaseless encoding uses harmonic modulation of the longitudinal magnetization with different frequencies and phases before excitation. It can be combined with Fourier encoding of complementary dimensions to produce, e.g., a 3D version of echo planar imaging insensitive to intershot phase variations. It can also be mixed with Fourier encoding of the same dimension allowing a high-resolution image to be obtained from magnitude-reconstructed low-resolution components. The latter is a generalization of the super-resolution MRI with microscopic tagging proposed recently. Improved reconstruction for this technique was adopted from its optical analogue, harmonic excitation light microscopy (HELM). Results Artifact free images were obtained despite phase fluctuations caused by random receiver reference and object motion during diffusion weighting. Proposed reconstruction of mixed-encoded data reaches higher resolution than the original super-resolution method. Conclusion Spatial information can be encoded in the magnitude of the MR signal rendering the experiment insensitive to phase fluctuations. Magn Reson Med 78:1029-1037, 2017. © 2016 International Society for Magnetic Resonance in Medicine [ABSTRACT FROM AUTHOR]

Metamaterials are artificial structures composed of subwavelength unit cells to control electromagnetic (EM) waves. The spatial coding representation of metamaterial has the ability to describe the material in a digital way. The spatial coding metamaterials are typically constructed by unit cells that have similar shapes with fixed functionality. Here, the concept of frequency coding metamaterial is proposed, which achieves different controls of EM energy radiations with a fixed spatial coding pattern when the frequency changes. In this case, not only different phase responses of the unit cells are considered, but also different phase sensitivities are also required. Due to different frequency sensitivities of unit cells, two units with the same phase response at the initial frequency may have different phase responses at higher frequency. To describe the frequency coding property of unit cell, digitalized frequency sensitivity is proposed, in which the units are encoded with digits “0” and “1” to represent the low and high phase sensitivities, respectively. By this merit, two degrees of freedom, spatial coding and frequency coding, are obtained to control the EM energy radiations by a new class of frequency‐spatial coding metamaterials. The above concepts and physical phenomena are confirmed by numerical simulations and experiments. [ABSTRACT FROM AUTHOR]

We propose a multi-mode nonlinear interferometer and study its phase sensitivity for two, three and four modes with single photons as inputs. We find that the phase sensitivity of the nonlinear interferometers can be improved by increasing the nonlinear index k. And when the total number of the input photons is fixed, increasing the number of modes is detrimental to the phase sensitivity. [ABSTRACT FROM AUTHOR]

We propose a scheme to improve the phase sensitivity of a Mach–Zehnder interferometer. In this scheme, a Kerr nonlinear phase shifter is used to replace the traditional linear phase shifter. We consider two detection approaches: the direct homodyne detection (DHD) and the indirect homodyne detection (IHD). We find that the Kerr nonlinear phase shifter can improve the phase sensitivity of the interferometer, and the DHD is better than the IHD. In addition, we also find that the phase sensitivity of the Kerr nonlinear interferometer is robust against photon losses. [ABSTRACT FROM PUBLISHER]

We investigate the dependence of phase sensitivity and entanglement of two streams of photons that they incident upon Mach-Zehnder interferometer on the initial input states and the phase difference. Phase sensitivity and entanglement are periodic function of the phase difference. The initial input state with the more photons or smaller population difference induces the better phase sensitivity and entanglement. [ABSTRACT FROM AUTHOR]

We investigate the reciprocal of the mean quantum Fisher information per particle (RMQFIP) and phase sensitivity of atomic Josephson junctions with a bosonic species confined by a double-well potential. Here we are focus on the Rabi oscillation energy's influence on RMQFIP and phase sensitivity. The better quantum entanglement and phase sensitivity may be achieved by decreasing the Rabi oscillation energy. [ABSTRACT FROM AUTHOR]

We consider isochrons of a periodic orbit in the planar FitzHugh-Nagumo system, that is, the curves of points that converge to the periodic orbit in phase with each other, and we extend this notion to isochrons of a focus equilibrium. We introduce the notion of backward-time isochrons, which are isochrons of the reversed-time system, and show that a cubic tangency occurs between a set of forward-time and backward-time isochrons. We call this moment of tangency a cubic isochron foliation tangency (CIFT). This phenomenon is not a local feature but happens globally throughout the annulus where both sets of isochrons coexist. We construct and discuss examples for three mechanisms for a CIFT: a global time-scale separation; a perturbation that increases the velocity along trajectories in a local region of phase space; and a canard explosion (in the Van der Pol system). [ABSTRACT FROM AUTHOR]

We propose a scheme for preparing multi-photon entangled state which is useful for sub-shot-noise sensitivity with beam splitter, where the entangled degree is measured by the reciprocal of the mean quantum Fisher information per particle (RMQFIP). The multi-photon entangled state can be prepared by adjusting the transmissivity of the beam splitter and the better multi-photon entangled state can be prepared by increasing the total number of photons. [ABSTRACT FROM AUTHOR]

I investigate the dependence of phase sensitivity on the initial input states. By adopting frozen-spin approximation, I first derive the analytical expresses of the angular momentum operators and then of quantum Fisher information, the phase sensitivity. It is shown that the initial input state with smaller value of angular momentum has the better degree of entanglement and phase sensitivity beats the Heisenberg limit. [ABSTRACT FROM AUTHOR]

By using phase space method, we theoretically investigate the quantum statistical properties and quantum interference of optical parametric amplification of single photon. The statistical properties, such as the Wigner function (WF), average photon number, photon number distribution and parity, are derived analytically for the fields of the two output ports. The results indicate that the fields in the output ports are multiphoton states rather than single photon state due to the amplification of the optical parametric amplifiers (OPA). In addition, the phase sensitivity is also examined by using the detection scheme of parity measurement. [ABSTRACT FROM AUTHOR]

We investigate the phase sensitivity of a collection of interacting spins with quantum Fisher information controlled by an external field. By adopting the frozen-spin approximation, we derive the approximate analytical expressions of the maximal quantum Fisher information and the phase sensitivity. It is shown that the maximal quantum Fisher information and the phase sensitivity depend on the strength of the external field. With the increases of the external field, the period of oscillation of quantum Fisher information and phase estimation decrease, while the values of quantum Fisher information and phase sensitivity increase because of the suppress by the external field. [ABSTRACT FROM AUTHOR]

Surface Plasmon Resonance (SPR) has become a central tool for label-free characterization of biomolecular interactions. Based on monitoring of amplitude characteristics, conventional SPR sensors have been extensively explored, commercialized and applied for studies of many important interactions (antigen-antibody, protein-ligand etc), but this technology still lacks of sensitivity for the detection of relatively small and low copy number compounds. Phase-sensitive SPR has recently emerged as an upgrade of this technology to resolve the sensitivity issue. Profiting from a sharp phase jump under SPR and ultra-sensitive tools of its control, this technology offers up to 100-time improvement of the detection limit, giving access to the detection of trace amounts of small molecular weight analytes (drugs etc). This paper intends to provide a tutorial on basic concepts of phase detection in SPR sensing, compare the performance of phase- and amplitude-sensitive sensors, review recent progress in the development and applications of phase-sensitive SPR sensors, and outline future prospects and trends of this technology. [ABSTRACT FROM AUTHOR]

We investigate we investigate the quantum Fisher information and phase sensitivity in Yurke-like state superposed by two special multi-particle states and a symmetric state with relative phase. By studying the influences of superposition coefficients and relative phase on the maximal quantum Fisher information and phase sensitivity, we reveal some entanglement properties of Yurke-like state. [ABSTRACT FROM AUTHOR]

Using the phase space method, we study the quantum interference through a Mach–Zehnder interferometer with an arbitrary-photon Fock state and a coherent state as two inputs. The statistical properties, in terms of the Wigner function, average photon number, photon number distribution and parity, are derived analytically for the field of the individual output port. These results indicate that the output state is actually a statistical mixture between a bunch of Fock state and coherent states. In addition, the phase sensitivity is also examined by using the detection scheme of intensity difference measurement. [ABSTRACT FROM AUTHOR]

A theory is developed for local, first-order sensitivity analysis of limit-cycle oscillating hybrid systems, which are dynamical systems exhibiting both continuous-state and discrete-state dynamics whose state trajectories are closed, isolated, and time-periodic. Methods for the computation of initial-condition sensitivities and parametric sensitivities are developed to account exactly for any jumps in the sensitivities at discrete transitions and to exploit the time-periodicity of the system, It is shown that the initial-condition sensitivities of any limit-cycle oscillating hybrid system can be represented as the sum of a time-decaying component and a time-periodic component so that they become periodic in the long-time limit. A method is developed for decomposition of the parametric sensitivities into three parts, characterizing the influence of parameter changes on period, state variable amplitudes, and relative phases, respectively. The computation of parametric sensitivities of period, amplitudes, and different types of phases is also described. The methods developed in this work are applied to particular models for illustration, including models exhibiting state variable jumps. [ABSTRACT FROM AUTHOR]

Boundary value formulations are presented for exact and efficient sensitivity analysis, with respect to model parameters and initial conditions, of different classes of oscillating systems. Methods for the computation of sensitivities of derived quantities of oscillations such as period, amplitude, and different types of phases are first developed for limit-cycle oscillators. In particular, a novel decomposition of the state sensitivities into three parts is proposed to provide an intuitive classification of the influence of parameter changes on period, amplitude, and relative phase. The importance of the choice of time reference, i.e., the phase locking condition, is demonstrated and discussed, and its influence on the sensitivity solution is quantified. The methods are then extended to other classes of oscillatory systems in a general formulation. Numerical techniques are presented to facilitate the solution of the boundary value problem and the computation of different types of sensitivities. Numerical results are verified by demonstrating consistency with finite difference approximations and are superior both in computational efficiency and in numerical precision to existing partial methods. [ABSTRACT FROM AUTHOR]

An echolocating bat produces echoes consisting of the convolution of echolocation call and the impulse response (IR) of the ensonified object. A crucial question in animal sonar is whether bats are able to extract this IR from the echo. The bat inner ear generates a frequency representation of call and echo and IR extraction in the frequency domain requires accurate analysis of both magnitude and phase information. Previous studies investigating the phase sensitivity of bats using a jitter paradigm reported a temporal acuity down to 10 ns, suggesting perfect sonar phase representation. In a phantom-target playback experiment, we investigate the perceptual phase sensitivity of the bat Phyllostomus discolor using a novel approach: instead of manipulating IR phase by changing IR delay (jitter paradigm), we randomized IR phase and thus lengthened the IR over time, leaving the magnitude spectrum unchanged. Our results show that phase sensitivity, as reflected in the analysis of signal duration, appears to be much lower than phase sensitivity, as reflected in the analysis of signal onset. The current data indicate that different temporal aspects of sonar processing are encoded with very different temporal resolution and thus an overall claim of “phase sensitivity” as such cannot be maintained. [ABSTRACT FROM AUTHOR]

We demonstrate the characterization of optical sources with high sensitivity, high temporal resolution, and phase sensitivity using linear optical sampling. Eye diagrams and constellation diagrams are reconstructed using the interference of the source under test with a train of sampling pulses. This concept is implemented using a waveguide optical hybrid, which splits and recombines the sources and adjusts the phase between the recombined signals to provide optimal detection. This diagnostic is used to characterize on-off keyed (OOK) waveforms at rates up to 640 Gb/s and various phase-shift keyed (PSK) signals at 10 and 40 Gb/s. [ABSTRACT FROM PUBLISHER]

Nonspecific surface binding of small protein molecules presents a major obstacle to surface biosensing techniques attempting to detect very low concentrations (< 1 pg/mm2) of large biological objects such as cells and bacteria. A new method for selective desensitization of a polarimetric waveguide interferometer eliminates the background noise from nonspecific surface binding. We demonstrate the ability to tune the phase sensitivity of a waveguide interferometer as a function of the distance of the biological or chemical analyte from the waveguide surface. This makes possible a sensor that has zero sensitivity at a particular distance where nonspecific surface binding occurs without significantly reducing the sensitivity to target larger biological species [ABSTRACT FROM PUBLISHER]

The electric organ discharge (EOD) of the South American knifefish Eigenmannia sp. is a permanently present wave signal of usually constant amplitude and frequency (similar to a sine wave). A fish perceives discharges of other fish as a modulation of its own. At frequency identity (ΔF = 0 Hz) the phase difference between a fish's own electric discharge and that of another fish affects the superimposed waveform. It was unclear whether or not the electrosensory stimulus-intensity threshold as behaviourally determined depends on the phase difference between a fish's own EOD and a sine-wave stimulus (at ΔF = 0 Hz). Also the strength of the jamming avoidance response (JAR), a discharge frequency shift away from a stimulus that is sufficiently close to the EOD frequency, as a function of phase difference was studied. Sine-wave stimuli were both frequency-clamped and phase-locked to a fish's discharge frequency (ΔF = 0 Hz). In food-rewarded fish, the electrosensory stimulus-intensity threshold depended significantly on the phase difference between a fish's discharge and the stimulus. Stimulus-intensity thresholds were low (down to 3 μV/cm, peak-to-peak) when the superimposed complex wave changed such that the shift in zero-crossings times relative to the original EOD was large but amplitude change minimal; stimulus-intensity thresholds were high (up to 16.9 μV/cm, peak-to-peak) when the shift in zero-crossings times was small but amplitude change maximal. Similar results were obtained for the non-conditioned JAR: at constant supra-threshold stimulus intensities and ΔF = 0 Hz, the phase difference significantly affected the strength of the JAR, although variability between individuals was higher than that observed in the conditioned experiments. [ABSTRACT FROM AUTHOR]

The hypothesis is advanced that certain inhibitory processes necessarily involve autonomic adjustments. Such adjustments would represent a constraint on information processing imposed by the location of the mind in a body. Evidence is reviewed showing that motoric inhibition is related to a transient delay in heartbeat generation. The delay is shown to further depend upon when inhibition occurs in the cardiac cycle. It is argued that this form of interaction between central and autonomic nervous system processing may be common. Central nervous system processes that may control inhibition and integrate information processing with motoric and autonomic processes are discussed. [ABSTRACT FROM AUTHOR]

We attempted to demonstrate that significant perceptual stimuli would induce different degrees of heart rate deceleration depending on when (phase) in the cardiac cycle they occurred. Relative to previous work, we concurrently examined a number of factors that might alter the amplitude of such a cardiac cycle time effect. Stimulus intensity and presence or absence of a speeded response were manipulated. Liminal stimuli and a perceptual rather than motor set were expected to maximize any cardiac cycle time effect. Respiratory phase, length of average interbeat interval, and number of trials were also investigated. Twenty-four college aged, male volunteers were randomly separated into equal groups receiving instructions either to judge which of two weak visual stimuli occurred or to execute a speeded, discriminative response to the stimuli. Discriminative stimuli were presented at either 0, 150, 250, 350, or 500 ms after the R-wave of the electrocardiogram. Stimuli were presented with an intensity that had yielded either 63% or 90% correct detections in a prior psychophysical assessment. A phase dependent deceleration occurred after both intensities of stimuli. Poststimulus deceleration was greater for stimuli in early to mid cycle as suggested by earlier work. As expected, this result was clear when the stimuli were presented during the expiratory phase of respiration. Neither perceptual/motor set nor stimulus intensity altered the phase sensitive deceleration. Thus, phase sensitive deceleration was confirmed using demanding sensory stimuli and an improved representational technique. [ABSTRACT FROM AUTHOR]

Interferometric fiber-optic hydrophones are an important means in the field of underwater acoustic detection. The design of the hydrophone sensor head is the key technology related to its detection sensitivity. In this paper, a high-sensitivity cuboid interferometric fiber-optic hydrophone based on planar rectangular film sensing is proposed, and the sensitivity of the sensor is compared with that of the widely used air-backed mandrel hydrophone under the same conditions. The acoustic characteristic models of the two types of sensors were established by theoretical calculation and simulation analysis to obtain the theoretical pressure sensitivity. Some experiments were performed to examine the theory and design. According to the experiment results, the mean phase sensitivity of the mandrel type was −112.85 dB re 1 rad/μPa in the operating frequency range of 10–300 Hz, and that of the cuboid type was −84.50 dB re 1 rad/μPa. The latter was 28.35 dB higher than the former was. These results are useful for improving hydrophone sensitivity. [ABSTRACT FROM AUTHOR]