scholarly journals Spatio–temporal entanglement of twin photons: An intuitive picture

2014 ◽  
Vol 12 (02) ◽  
pp. 1461016 ◽  
Author(s):  
Alessandra Gatti ◽  
Lucia Caspani ◽  
Tommaso Corti ◽  
Enrico Brambilla ◽  
Ottavia Jedrkiewicz
Keyword(s):  
Quantum Entanglement ◽  
Wave Packets ◽  
Temporal Structure ◽  
Space Time ◽  
Entangled State ◽  
Temporal Properties ◽  
Classical Wave ◽  
Spatio Temporal

We draw an intuitive picture of the spatio–temporal properties of the entangled state of twin photons, where they are described as classical wave-packets. This picture predicts a precise relation between their temporal and transverse spatial separations at the crystal output. The space-time coupling described by classical arguments turns out to determine in a precise way the spatio–temporal structure of the quantum entanglement, analyzed by means of the biphotonic correlation and of the Schmidt dimensionality of the entanglement.

scholarly journals Hybrid guided space-time optical modes in unpatterned films

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Abbas Shiri ◽  
Murat Yessenov ◽  
Scott Webster ◽  
Kenneth L. Schepler ◽  
Ayman F. Abouraddy
Keyword(s):  
Boundary Conditions ◽  
Wave Packets ◽  
Temporal Structure ◽  
Transverse Dimension ◽  
Silica Film ◽  
Space Time ◽  
Planar Waveguides ◽  
Group Index ◽  
Optical Modes ◽  
Spatio Temporal

AbstractLight is confined transversely and delivered axially in a waveguide. However, waveguides are lossy static structures whose modal characteristics are fundamentally determined by their boundary conditions. Here we show that unpatterned planar waveguides can provide low-loss two-dimensional waveguiding by using space-time wave packets, which are unique one-dimensional propagation-invariant pulsed optical beams. We observe hybrid guided space-time modes that are index-guided in one transverse dimension and localized along the unbounded dimension. We confirm that these fields enable overriding the boundary conditions by varying post-fabrication the group index of the fundamental mode in a 2-μm-thick, 25-mm-long silica film, achieved by modifying the field’s spatio-temporal structure. Tunability of the group index over an unprecedented range from 1.26 to 1.77 is verified while maintaining a spectrally flat zero-dispersion profile. Our work paves the way to utilizing space-time wave packets in on-chip platforms, and enable phase-matching strategies that circumvent restrictions due to intrinsic material properties.

scholarly journals The Response of Microwave Emission to the Development of Active Regions

1986 ◽  
Vol 7 ◽  
pp. 755-757
Author(s):  
G. Ya. Smolkov
Keyword(s):  
Active Region ◽  
Temporal Structure ◽  
Active Regions ◽  
Microwave Emission ◽  
Degree Of Polarization ◽  
Emission Characteristics ◽  
Eclipse Observations ◽  
Temporal Properties ◽  
Spatio Temporal ◽  
Main Components

As is known from eclipse observations, the microwave emission of an active region consists of three main components: floccular, inter-spot (halo) and spot components which differ in intensity, the degree of polarization, and in structure and sizes /1/. A possibility of identifying the finer spatial and temporal structure in the active region (AR) emission has existed since RATAN, the VLA and WSRT became operational. The construction of the SSRT permitted the initiation of a systematic study of spatio-temporal properties of the development of active regions /2, 3/.The majority of the properties in the AR development are reflected in detail and rapidly in the microwave emission characteristics /4, 6/.

Spatio-temporal structure of the wave packets generated by the solar terminator

2009 ◽  
Vol 44 (7) ◽  
pp. 824-835 ◽  
Author(s):  
E.L. Afraimovich ◽  
I.K. Edemskiy ◽  
S.V. Voeykov ◽  
Yu.V. Yasyukevich ◽  
I.V. Zhivetiev
Keyword(s):  
Wave Packets ◽  
Temporal Structure ◽  
Solar Terminator ◽  
Spatio Temporal

scholarly journals Spatio-temporal analysis of flood data from South Carolina

2020 ◽  
Vol 7 (1) ◽  
Author(s):  
Haigang Liu ◽  
David B. Hitchcock ◽  
S. Zahra Samadi
Keyword(s):  
South Carolina ◽  
Temporal Structure ◽  
Daily Rainfall ◽  
Temporal Analysis ◽  
The United States ◽  
Environmental Data ◽  
Temporal Properties ◽  
Proximity Matrix ◽  
Spatio Temporal ◽  
Emergency Decision

AbstractTo investigate the relationship between flood gage height and precipitation in South Carolina from 2012 to 2016, we built a conditional autoregressive (CAR) model using a Bayesian hierarchical framework. This approach allows the modelling of the main spatio-temporal properties of water height dynamics over multiple locations, accounting for the effect of river network, geomorphology, and forcing rainfall. In this respect, a proximity matrix based on watershed information was used to capture the spatial structure of gage height measurements in and around South Carolina. The temporal structure was handled by a first-order autoregressive term in the model. Several covariates, including the elevation of the sites and effects of seasonality, were examined, along with daily rainfall amount. A non-normal error structure was used to account for the heavy-tailed distribution of maximum gage heights. The proposed model captured some key features of the flood process such as seasonality and a stronger association between precipitation and flooding during summer season. The model is able to forecast short term flood gage height which is crucial for informed emergency decision. As a byproduct, we also developed a Python library to retrieve and handle environmental data provided by some main agencies in the United States. This library can be of general usefulness for studies requiring rainfall, flow, and geomorphological information over specific areas of the conterminous US.

scholarly journals Faster is better: Visual responses to motion are stronger for higher refresh rates

2018 ◽  
Author(s):  
Mina A.Khoei ◽  
Francesco Galluppi ◽  
Quentin Sabatier ◽  
Pierre Pouget ◽  
Benoit R Cottereau ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Human Subjects ◽  
Temporal Structure ◽  
Temporal Information ◽  
Visual Responses ◽  
General Belief ◽  
Temporal Properties ◽  
Low Pass ◽  
Spatio Temporal ◽  
Multiple Species

Although neural responses with a millisecond precision were reported in the retina, lateral geniculate nucleus and visual cortex of multiple species, the presence and role of such a fine temporal structure is still debated at the cortical level and the general belief remains that early visual system encodes information at slower timescales. In this study, we used a new stimulation platform to generate visual stimuli that were very precisely encoded in time and we characterized in human subjects the EEG responses to moving patterns that shared the same global motion but differed in their fine scale spatio-temporal properties. In two experiments, we manipulated the information within temporal windows that corresponded to the frame duration in conventional (1/60 = 16.7ms, experience 1) and more recent (1/120 = 8.3ms, experience 2) visual displays. Our results demonstrate that EEG responses to temporally dense and coherent trajectories are significantly stronger than those to control conditions without these properties. They extend previous results from our group that showed that accurate temporal information (<10ms) significantly improve perceptual judgments on spatial discrimination, digit recognition and sensitivity for speed [Kime et al., 2016]. Altogether, our results suggest that instead of low-pass filtering the temporal information it receives from its thalamic afferents, the visual cortex may actually exploit its richness to improve visual perception.

scholarly journals Free-space optical delay line using space-time wave packets

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Murat Yessenov ◽  
Basanta Bhaduri ◽  
Peter J. Delfyett ◽  
Ayman F. Abouraddy
Keyword(s):  
Free Space ◽  
Delay Line ◽  
Wave Packets ◽  
Space Time ◽  
Free Space Optical ◽  
Optical Delay Line ◽  
Communications Networks ◽  
Optical Delay ◽  
All Optical ◽  
Spatio Temporal

AbstractAn optical buffer featuring a large delay-bandwidth-product—a critical component for future all-optical communications networks—remains elusive. Central to its realization is a controllable inline optical delay line, previously accomplished via engineered dispersion in optical materials or photonic structures constrained by a low delay-bandwidth product. Here we show that space-time wave packets whose group velocity is continuously tunable in free space provide a versatile platform for constructing inline optical delay lines. By spatio-temporal spectral-phase-modulation, wave packets in the same or in different spectral windows that initially overlap in space and time subsequently separate by multiple pulse widths upon free propagation by virtue of their different group velocities. Delay-bandwidth products of  ~100 for pulses of width  ~1 ps are observed, with no fundamental limit on the system bandwidth.

scholarly journals A spatio-temporal specification language and its completeness & decidability

2020 ◽  
Vol 9 (1) ◽  
Author(s):  
Tengfei Li ◽  
Jing Liu ◽  
Haiying Sun ◽  
Xiang Chen ◽  
Lipeng Zhang ◽  
...  
Keyword(s):  
Intelligent Transportation System ◽  
Cyber Physical Systems ◽  
Specification Language ◽  
Finite Model ◽  
Critical Systems ◽  
Physical Systems ◽  
Spatial Objects ◽  
Temporal Properties ◽  
Spatio Temporal ◽  
Temporal Specification

AbstractIn the past few years, significant progress has been made on spatio-temporal cyber-physical systems in achieving spatio-temporal properties on several long-standing tasks. With the broader specification of spatio-temporal properties on various applications, the concerns over their spatio-temporal logics have been raised in public, especially after the widely reported safety-critical systems involving self-driving cars, intelligent transportation system, image processing. In this paper, we present a spatio-temporal specification language, STSL PC, by combining Signal Temporal Logic (STL) with a spatial logic S4 u, to characterize spatio-temporal dynamic behaviors of cyber-physical systems. This language is highly expressive: it allows the description of quantitative signals, by expressing spatio-temporal traces over real valued signals in dense time, and Boolean signals, by constraining values of spatial objects across threshold predicates. STSL PC combines the power of temporal modalities and spatial operators, and enjoys important properties such as finite model property. We provide a Hilbert-style axiomatization for the proposed STSL PC and prove the soundness and completeness by the spatio-temporal extension of maximal consistent set and canonical model. Further, we demonstrate the decidability of STSL PC and analyze the complexity of STSL PC. Besides, we generalize STSL to the evolution of spatial objects over time, called STSL OC, and provide the proof of its axiomatization system and decidability.

Spatio-temporal visual properties in the ascending tectofugal system

2010 ◽  
Vol 5 (1) ◽  
pp. 21-30 ◽  
Author(s):  
Alice Rokszin ◽  
Zita Márkus ◽  
Gábor Braunitzer ◽  
Antal Berényi ◽  
Marek Wypych ◽  
...  
Keyword(s):  
Visual Information ◽  
Frequency Tuning ◽  
Temporal Frequency ◽  
Neuronal Population ◽  
Neuronal Responses ◽  
Temporal Properties ◽  
Visual Receptive Field ◽  
Detailed Statistical Analysis ◽  
Spatio Temporal ◽  
Visual Properties

AbstractOur study compares the spatio-temporal visual receptive field properties of different subcortical stages of the ascending tectofugal visual system. Extracellular single-cell recordings were performed in the superficial (SCs) and intermediate (SCi) layers of the superior colliculus (SC), the suprageniculate nucleus (Sg) of the posterior thalamus and the caudate nucleus (CN) of halothane-anesthetized cats. Neuronal responses to drifting gratings of various spatial and temporal frequencies were recorded. The neurons of each structure responded optimally to low spatial and high temporal frequencies and displayed narrow spatial and temporal frequency tuning. The detailed statistical analysis revealed that according to its stimulus preferences the SCs has markedly different spatio-temporal properties from the homogeneous group formed by the SCi, Sg and CN. The SCs neurons preferred higher spatial and lower temporal frequencies and had broader spatial tuning than the other structures. In contrast to the SCs the visually active SCi, as well as the Sg and the CN neurons possessed consequently similar spatio-temporal preferences. These data support our hypothesis that the visually active SCi, Sg and CN neurons form a homogeneous neuronal population given a similar spatio-temporal frequency preference and a common function in processing of dynamic visual information.

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