Journal articles: 'Coherence gate'

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Graf, Benedikt W., Steven G. Adie, and Stephen A. Boppart. "Correction of coherence gate curvature in high numerical aperture optical coherence imaging." Optics Letters 35, no. 18 (September 15, 2010): 3120. http://dx.doi.org/10.1364/ol.35.003120.

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DING, ZHIHUA, YANG NI, and JIE MENG. "AXIAL SUPERRESOLUTION BY PHASE FILTER IN OPTICAL COHERENCE TOMOGRAPHY." Journal of Innovative Optical Health Sciences 05, no. 04 (October 2012): 1250022. http://dx.doi.org/10.1142/s1793545812500228.

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Axial superresolution in optical coherence tomography (OCT) by a three-zone annular phase filter is demonstrated. In the proposed probe of a spectral domain OCT system, the width of the central lobe of the axial intensity point spread function is apodized by the filter to be within the coherence gate determined by the light source, while its sidelobes are lying outside the coherence gate without contributing to the coherence imaging. By measurement of the depth response of the OCT system before and after inserting the filter, an improvement of about 20% in axial resolution is confirmed. OCT imaging on biological sample of orange fresh is also conducted, demonstrating increased depth discrimination without the negative contribution from sidelobes realized by the phase filter in combination with the coherence gate intrinsic to OCT. It comes to a conclusion that we can obtain axial superresolution by filter in OCT system without the degrading influence of large sidelobes.

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Pokorný, Jiří, Jan Pokorný, Alberto Foletti, Jitka Kobilková, Jan Vrba, and Jan Vrba. "Mitochondrial Dysfunction and Disturbed Coherence: Gate to Cancer." Pharmaceuticals 8, no. 4 (September 30, 2015): 675–95. http://dx.doi.org/10.3390/ph8040675.

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Baer, Roi, and Daniel Neuhauser. "Anti-coherence based molecular electronics: XOR-gate response." Chemical Physics 281, no. 2-3 (August 2002): 353–62. http://dx.doi.org/10.1016/s0301-0104(02)00570-0.

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Laucht, Arne, Juha T. Muhonen, Fahd A. Mohiyaddin, Rachpon Kalra, Juan P. Dehollain, Solomon Freer, Fay E. Hudson, et al. "Electrically controlling single-spin qubits in a continuous microwave field." Science Advances 1, no. 3 (April 2015): e1500022. http://dx.doi.org/10.1126/sciadv.1500022.

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Large-scale quantum computers must be built upon quantum bits that are both highly coherent and locally controllable. We demonstrate the quantum control of the electron and the nuclear spin of a single31P atom in silicon, using a continuous microwave magnetic field together with nanoscale electrostatic gates. The qubits are tuned into resonance with the microwave field by a local change in electric field, which induces a Stark shift of the qubit energies. This method, known asA-gate control, preserves the excellent coherence times and gate fidelities of isolated spins, and can be extended to arbitrarily many qubits without requiring multiple microwave sources.

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Ni, Kang-Kuen, Till Rosenband, and David D. Grimes. "Dipolar exchange quantum logic gate with polar molecules." Chemical Science 9, no. 33 (2018): 6830–38. http://dx.doi.org/10.1039/c8sc02355g.

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Folk, J. A. "A Gate-Controlled Bidirectional Spin Filter Using Quantum Coherence." Science 299, no. 5607 (January 31, 2003): 679–82. http://dx.doi.org/10.1126/science.1078419.

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Sun, Shih-Jye, Miroslav Menšík, Petr Toman, Cheng-Han Chung, Chimed Ganzorig, and Jiří Pfleger. "Gate voltage impact on charge mobility in end-on stacked conjugated oligomers." Physical Chemistry Chemical Physics 22, no. 15 (2020): 8096–108. http://dx.doi.org/10.1039/c9cp06477j.

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Kawakami, Erika, Thibaut Jullien, Pasquale Scarlino, Daniel R. Ward, Donald E. Savage, Max G. Lagally, Viatcheslav V. Dobrovitski, et al. "Gate fidelity and coherence of an electron spin in an Si/SiGe quantum dot with micromagnet." Proceedings of the National Academy of Sciences 113, no. 42 (October 3, 2016): 11738–43. http://dx.doi.org/10.1073/pnas.1603251113.

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The gate fidelity and the coherence time of a quantum bit (qubit) are important benchmarks for quantum computation. We construct a qubit using a single electron spin in an Si/SiGe quantum dot and control it electrically via an artificial spin-orbit field from a micromagnet. We measure an average single-qubit gate fidelity of ∼99% using randomized benchmarking, which is consistent with dephasing from the slowly evolving nuclear spins in the substrate. The coherence time measured using dynamical decoupling extends up to ∼400 μs for 128 decoupling pulses, with no sign of saturation. We find evidence that the coherence time is limited by noise in the 10-kHz to 1-MHz range, possibly because charge noise affects the spin via the micromagnet gradient. This work shows that an electron spin in an Si/SiGe quantum dot is a good candidate for quantum information processing as well as for a quantum memory, even without isotopic purification.

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Borilovic, Ivana, Pablo J. Alonso, Olivier Roubeau, and Guillem Aromí. "A bis-vanadyl coordination complex as a 2-qubit quantum gate." Chemical Communications 56, no. 21 (2020): 3139–42. http://dx.doi.org/10.1039/c9cc09817h.

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A divanadyl complex anion is isolated through a new bis-hydroxyphenylpyrazolyl ligand and has optimal weak dipolar coupling and quantum coherence to implement electron-mediated nuclear quantum simulations in a 2-qubit molecular architecture.

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Bykov, A. A., E. B. Olshanetsky, L. V. Litvin, N. T. Moshegov, A. I. Toropov, and G. M. Gusev. "Coherence properties of submicron GaAs/AlGaAs rings with a ferromagnetic gate." Physica E: Low-dimensional Systems and Nanostructures 2, no. 1-4 (July 1998): 408–11. http://dx.doi.org/10.1016/s1386-9477(98)00084-8.

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Chiacchio, Ferdinando, Jose Ignacio Aizpurua, Diego D'Urso, and Lucio Compagno. "Coherence region of the Priority-AND gate: Analytical and numerical examples." Quality and Reliability Engineering International 34, no. 1 (November 10, 2017): 107–15. http://dx.doi.org/10.1002/qre.2241.

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Güler, Marifi. "Stochastic Hodgkin-Huxley Equations with Colored Noise Terms in the Conductances." Neural Computation 25, no. 1 (January 2013): 46–74. http://dx.doi.org/10.1162/neco_a_00384.

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The excitability of cells is facilitated by voltage-gated ion channels. These channels accommodate a multiple number of gates individually. The possible impact of that gate multiplicity on the cell's function, specifically when the membrane area is of limited size, was investigated in the author's prior work (Güler, 2011 ). There, it was found that a nontrivially persistent correlation takes place between the transmembrane voltage fluctuations (also between the fluctuations in the gating variables) and the component of open channel fluctuations attributed to the gate multiplicity. This nontrivial phenomenon was found to be playing a major augmentative role for the elevation of excitability and spontaneous firing in small cells. In addition, the same phenomenon was found to be enhancing spike coherence significantly. Here we extend Fox and Lu's ( 1994 ) stochastic Hodgkin-Huxley equations by incorporating colored noise terms into the conductances there to obtain a formalism capable of capturing the addressed cross-correlations. Statistics of spike generation, spike coherence, firing efficiency, latency, and jitter from the articulated set of equations are found to be highly accurate in comparison with the corresponding statistics from the exact microscopic Markov simulations. This way, it is demonstrated vividly that our formulation overcomes the inherent inadequacy of the Fox and Lu equations. Finally, a recently proposed diffusion approximation method (Linaro, Storace, & Giugliano, 2011 ) is taken into consideration, and a discussion on its character is pursued.

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Grebenyuk, Anton A., and Vladimir P. Ryabukho. "Numerical correction of coherence gate in full-field swept-source interference microscopy." Optics Letters 37, no. 13 (June 21, 2012): 2529. http://dx.doi.org/10.1364/ol.37.002529.

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Wei, Wei, and Hao Ren. "Analysis on Flow-Induced Vibration of Underwater Horizontal Gate." Advanced Materials Research 163-167 (December 2010): 293–98. http://dx.doi.org/10.4028/www.scientific.net/amr.163-167.293.

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The best is to read these instructions and follow the outline of this text. The physical and numerical models were combined to analyze flow-induced vibration response of Qingshuihe River underwater horizontal gate in this paper; the pressures acting on the gate were divided into two parts: the fluctuating pressure of flow on the stationary gate and the hydrodynamic pressure caused by the gate vibration, which is additional pressure induced by disturbed flow. The temporal-spatial correlation of fluctuating pressures obtained by model experiments between different nodes was analyzed. In the study the coherence function is defined in frequency domain with consideration of different levels of correlation for different frequency components, and the nodal load of the fluctuating pressure could be obtained. A new distribution of additional mass with considering radial vibration of the gate is adopted as equivalent hydrodynamic pressure. Based on random vibration theory, the flow-induced vibration response of the gate was obtained. The results provide the reliable reference evidence for structural dynamic design of the gate and show that the hydrodynamic stability of the gate can meet the requirement. On the other hand, it is shown that this method is reasonable and feasible.

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Mądzik, Mateusz T., Thaddeus D. Ladd, Fay E. Hudson, Kohei M. Itoh, Alexander M. Jakob, Brett C. Johnson, Jeffrey C. McCallum, et al. "Controllable freezing of the nuclear spin bath in a single-atom spin qubit." Science Advances 6, no. 27 (July 2020): eaba3442. http://dx.doi.org/10.1126/sciadv.aba3442.

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The quantum coherence and gate fidelity of electron spin qubits in semiconductors are often limited by nuclear spin fluctuations. Enrichment of spin-zero isotopes in silicon markedly improves the dephasing time T2*, which, unexpectedly, can extend two orders of magnitude beyond theoretical expectations. Using a single-atom 31P qubit in enriched 28Si, we show that the abnormally long T2* is due to the freezing of the dynamics of the residual 29Si nuclei, caused by the electron-nuclear hyperfine interaction. Inserting a waiting period when the electron is controllably removed unfreezes the nuclear dynamics and restores the ergodic T2* value. Our conclusions are supported by a nearly parameter-free modeling of the 29Si nuclear spin dynamics, which reveals the degree of backaction provided by the electron spin. This study clarifies the limits of ergodic assumptions in nuclear bath dynamics and provides previously unidentified strategies for maximizing coherence and gate fidelity of spin qubits in semiconductors.

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Ďuriš, Miroslav, and Radim Chmelík. "Coherence gate manipulation for enhanced imaging through scattering media by non-ballistic light in partially coherent interferometric systems." Optics Letters 46, no. 18 (September 7, 2021): 4486. http://dx.doi.org/10.1364/ol.432484.

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Izatt, Joseph A., Manish Kulkarni, Hsing-Wen Wang, and Michael V. Sivak. "Optical Coherence Microscopy: A New Technique for High-Resolution, Non-Invasive Imaging in Bulk Biological Tissues." Microscopy and Microanalysis 3, S2 (August 1997): 795–96. http://dx.doi.org/10.1017/s1431927600010862.

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Optical coherence microscopy (OCM) is a novel technique complementary to optical coherence tomography (OCT) which combines low-coherence interferometry with confocal microscopy to achieve micron-scale resolution imaging in highly scattering media. OCM may be implemented using a single-mode fiber-optic low-coherence interferometer (See Fig. 1). A high numerical aperture objective is used to focus sample-arm light into the specimen, and the reference arm length of the interferometer is adjusted to match the sample arm focal plane optical depth. The sample arm of the interferometer comprises a scanning confocal microscope, in which either the sample or the probe beam is laterally scanned in a raster pattern, and the optical fiber acts as a single-mode confocal aperture for combined light illumination and collection. The reference arm length of the interferometer establishes the depth position of an interferometric “coherence gate” in the sample, from which backscattered light is preferentially collected. Initial studies of OCM in scattering phantoms have demonstrated that this technique provides increased optical sectioning depth compared to confocal microscopy alone.

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OLMSCHENK, S., D. HAYES, D. N. MATSUKEVICH, P. MAUNZ, D. L. MOEHRING, and C. MONROE. "QUANTUM LOGIC BETWEEN DISTANT TRAPPED IONS." International Journal of Quantum Information 08, no. 01n02 (February 2010): 337–94. http://dx.doi.org/10.1142/s0219749910006381.

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Trapped atomic ions have proven to be one of the most promising candidates for the realization of quantum computation due to their long trapping times, excellent coherence properties, and exquisite control of the internal atomic states. Integrating ions (quantum memory) with photons (distance link) offers a unique path to large-scale quantum computation and long-distance quantum communication. In this article, we present a detailed review of the experimental implementation of a heralded photon-mediated quantum gate between remote ions, and the employment of this gate to perform a teleportation protocol between two ions separated by a distance of about one meter.

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Jones, B. K., C. N. Graham, A. Konczakowska, and L. Hasse. "The coherence of the gate and drain noise in stressed AlGaAs–InAlGaAs PHEMTs." Microelectronics Reliability 41, no. 1 (January 2001): 87–97. http://dx.doi.org/10.1016/s0026-2714(00)00077-9.

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Jung, Hyun Hee, Joon Mo Yang, Won Myung Woo, Seung Ho Yi, J. S. Yang, and Kwang Sup Soh. "Signal Characteristics of Biophoton Emission from Human Hands." Key Engineering Materials 277-279 (January 2005): 96–101. http://dx.doi.org/10.4028/www.scientific.net/kem.277-279.96.

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The signal characteristics of the biophotons from human hands were studied using correlation and δ-value analyses. Three healthy individuals without any history of disease participated in the measurements, six times every Friday for 52 weeks, while staying in a room with dim lighting to eliminate any delayed luminescence caused by the sun or room lights. Two head-on type photomultiplier tubes inside a dark room were used to simultaneously measure the biophoton emissions from the palm and dorsum of the left and right hand with a 100ms gate time. In view of the signal process, a cross-correlation of the long-term data, i.e. the weekly measurements, revealed a strong correlation between the signals from the left and right hand, yet only a very weak correlation between the palm and dorsum. The non-classical light property of the biophotons, that has a quantum coherence nature, was compared with that of the dark counts of the PMTs using a δ- value analysis. The average δ-value for the biophotons was 0.08±0.07. As such, it was found that the palm emissions were very coherent, while the dorsum emissions showed an occasional lack of coherence.

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Wojtkowski, Maciej, Patrycjusz Stremplewski, Egidijus Auksorius, and Dawid Borycki. "Spatio-Temporal Optical Coherence Imaging – a new tool for in vivo microscopy." Photonics Letters of Poland 11, no. 2 (July 1, 2019): 44. http://dx.doi.org/10.4302/plp.v11i2.905.

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Optical Coherence Imaging (OCI) including Optical Coherence Tomography (OCT) and Optical Coherence Microscopy (OCM) uses interferometric detection to generate high-resolution volumetric images of the sample at high speeds. Such capabilities are significant for in vivo imaging, including ophthalmology, brain, intravascular imaging, as well as endoscopic examination. Instrumentation and software development allowed to create many clinical instruments. Nevertheless, most of OCI setups scan the incident light laterally. Hence, OCI can be further extended by wide-field illumination and detection. This approach, however, is very susceptible to the so-called crosstalk-generated noise. Here, we describe our novel approach to overcome this issue with spatio-temporal optical coherence manipulation (STOC), which employs spatial phase modulation of the incident light. Full Text: PDF ReferencesL. Wang, P. P. Ho, C. Liu, G. Zhang, and R. R. Alfano, "Ballistic 2-D Imaging Through Scattering Walls Using an Ultrafast Optical Kerr Gate", Science 253, 769-771 (1991). CrossRef D. Huang, E. A. Swanson, C. P. Lin, J. S. Schuman, W. G. Stinson, W. Chang, M. R. Hee, T. Flotte, K. Gregory, C. A. Puliafito, and et al., "Optical coherence tomography", Science 254, 1178-1181 (1991). CrossRef J. A. Izatt, E. A. Swanson, J. G. Fujimoto, M. R. Hee, and G. M. Owen, "Optical coherence microscopy in scattering media", Opt. Lett. 19, 590-592 (1994). CrossRef D. Borycki, M. Nowakowski, and M. Wojtkowski, "Control of the optical field coherence by spatiotemporal light modulation", Opt. Lett. 38, 4817-4820 (2013). CrossRef D. Borycki, M. Hamkalo, M. Nowakowski, M. Szkulmowski, and M. Wojtkowski, "Spatiotemporal optical coherence (STOC) manipulation suppresses coherent cross-talk in full-field swept-source optical coherence tomography", Biomed. Opt. Express 10, 2032-2054 (2019). CrossRef P. Stremplewski, E. Auksorius, P. Wnuk, L. Kozon, P. Garstecki, and M. Wojtkowski, "In vivo volumetric imaging by crosstalk-free full-field OCT", Optica 6, 608-617 (2019). CrossRef L. Vabre, A. Dubois, and A. C. Boccara, "Thermal-light full-field optical coherence tomography", Opt. Lett. 27, 530-532 (2002). CrossRef M. Laubscher, M. Ducros, B. Karamata, T. Lasser, and R. Salathé, "Video-rate three-dimensional optical coherence tomography", Opt. Express 10, 429-435 (2002). CrossRef Dubois and A. C. Boccara, Full-Field Optical Coherence Tomography, (Springer Berlin Heidelberg, Berlin, Heidelberg, 2008), pp. 565-591. CrossRef O. Thouvenin, K. Grieve, P. Xiao, C. Apelian, and A. C. Boccara, "En face coherence microscopy [Invited]", Biomedical Opt. Express 8, 622-639 (2017). CrossRef F. Fercher, C. K. Hitzenberger, M. Sticker, E. Moreno-Barriuso, R. Leitgeb, W. Drexler, and H. Sattmann, "A thermal light source technique for optical coherence tomography", Optics Commun. 185, 57-64 (2000). CrossRef R. A. Leitgeb, "En face optical coherence tomography: a technology review [Invited]", Biomed Opt Express 10, 2177-2201 (2019). CrossRef J. Fujimoto and W. Drexler, Introduction to Optical Coherence Tomography, (Springer, Berlin, Heidelberg, 2008), pp. 1-45. CrossRef J. A. Izatt, M. A. Choma, and A.-H. Dhalla, Theory of Optical Coherence Tomography, (Springer International Publishing, Cham, 2015), pp. 65-94. CrossRef

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23

AWSCHALOM, DAVID D. "CONTROLLING SPIN COHERENCE WITH SEMICONDUCTOR NANOSTRUCTURES." International Journal of Modern Physics B 22, no. 01n02 (January 20, 2008): 111–12. http://dx.doi.org/10.1142/s0217979208046165.

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We present two emerging opportunities for manipulating and communicating coherent spin states in semiconductors. First, we show that semiconductor microcavities offer unique means of controlling light-matter interactions in confined geometries, resulting in a wide range of applications in optical communications and inspiring proposals for quantum information processing and computational schemes. Studies of spin dynamics in microcavities — a new and promising research field — have revealed novel effects such as polarization beats, stimulated spin scattering, and giant Faraday rotation. Here, we study the electron spin dynamics in optically-pumped GaAs microdisk lasers with quantum wells and interface-fluctuation quantum dots in the active region. In particular, we examine how the electron spin dynamics are modified by the stimulated emission in the disks, and observe an enhancement of the spin coherence time when the optical excitation is in resonance with a high quality ( Q ~ 5000) lasing mode.1 This resonant enhancement, contrary to expectations from the observed trend in the carrier recombination time, is then manipulated by altering the cavity design and dimensions. In analogy to devices based on excitonic coherence, this ability to engineer coherent interactions between electron spins and photons may provide novel pathways towards spin dependent quantum optoelectronics. In a second example, the nitrogen-vacancy (N-V) center in diamond has garnered interest as a room-temperature solid-state system not only for exploring electronic and nuclear spin phenomena but also as a candidate for spin-based quantum information processing. Spin coherence times of up to 50 microseconds have been reported for ensembles of N-V centers and a two-qubit gate utilizing the electron spin of a N-V center and the nuclear spin of a nearby C-13 atom has been demonstrated. Here, we present experiments using angle-resolved magneto-photoluminescence microscopy to investigate anisotropic spin interactions of single N-V centers in diamond at room temperature.2 Negative peaks in the photoluminescence intensity are observed as a function of both magnetic field magnitude and angle, and can be explained by coherent spin precession and anisotropic relaxation at spin-level anticrossings. Additionally, precise field alignment with the symmetry axis of a single N-V center reveals the resonant magnetic dipolar coupling of a single "bright" electron spin of an N-V center to small numbers of "dark" spins of nitrogen defects in its immediate vicinity, which are otherwise undetected by photoluminescence. Most recently, we are exploring the possibility of utilizing this magnetic dipole coupling between bright and dark spins to couple two spatially separated single N-V center spins by means of intermediate nitrogen spins. Note from Publisher: This article contains the abstract only.

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Kimiaee Asadi, F., N. Lauk, S. Wein, N. Sinclair, C. O'Brien, and C. Simon. "Quantum repeaters with individual rare-earth ions at telecommunication wavelengths." Quantum 2 (September 13, 2018): 93. http://dx.doi.org/10.22331/q-2018-09-13-93.

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We present a quantum repeater scheme that is based on individual erbium and europium ions. Erbium ions are attractive because they emit photons at telecommunication wavelength, while europium ions offer exceptional spin coherence for long-term storage. Entanglement between distant erbium ions is created by photon detection. The photon emission rate of each erbium ion is enhanced by a microcavity with high Purcell factor, as has recently been demonstrated. Entanglement is then transferred to nearby europium ions for storage. Gate operations between nearby ions are performed using dynamically controlled electric-dipole coupling. These gate operations allow entanglement swapping to be employed in order to extend the distance over which entanglement is distributed. The deterministic character of the gate operations allows improved entanglement distribution rates in comparison to atomic ensemble-based protocols. We also propose an approach that utilizes multiplexing in order to enhance the entanglement distribution rate.

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Luo, Ming-Xing, and Hui-Ran Li. "Teleportation of a controlled-NOT gate for photon and electron-spin qubits assisted by the nitrogen-vacancy center." Quantum Information and Computation 15, no. 15&16 (November 2015): 1397–419. http://dx.doi.org/10.26421/qic15.15-16-9.

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Teleportations of quantum gates are very important in the construction of quantum network and teleportation-based model of quantum computation. Assisted with nitrogenvacancy centers, we propose several schemes to teleport the quantum CNOT gate. Deterministic CNOT gate may be implemented on a remote two-photon system, remote two electron-spin system, hybrid photon-spin system or hybrid spin-photon system. Each photon only interacts with one spin each time. Moreover, quantum channel may be constructed by all combinations of the photon or electron-spin entanglement, or their hybrid entanglement. Since these electron-spin systems have experimentally shown a long coherence time even at the room temperature, our schemes provide useful ways for long-distance quantum applications.

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West, Ryan M., Colby R. Watts, Mira Josowicz, and Jiří Janata. "Fluctuation analysis of work function of organic semiconductors." Collection of Czechoslovak Chemical Communications 76, no. 7 (2011): 843–58. http://dx.doi.org/10.1135/cccc2011055.

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We demonstrate, for the first time, work function fluctuations of a polyaniline film when used as the gate conductor of an insulated-gate field-effect transistor. The work function fluctuations induce drain current fluctuations, which are in excess of the channel noise of the transistor and the Nyquist noise of the polyaniline film. Using the fluctuation-dissipation theorem, it is determined that the fluctuations have a Lorentzian-like spectrum and are thermally activated with an activated energy of ca. 300 meV. The activation energy, as well as the corner frequency and magnitude of the fluctuations, depend on the applied electric field at the polyaniline–insulator interface. These results, along with coherence measurements, suggest that the fluctuations originate near the interface in the space-charge region of polyaniline. This technique provides kinetic and thermodynamic information about the gate conductor, at equilibrium, which cannot be extracted using other techniques that measure work function. Furthermore, by this technique it is possible to distinguish the fluctuations of the work function from the Nyquist noise. This approach should be generally applicable to any semiconducting material used as the gate conductor of a field-effect transistor.

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Virgili, Gianni, Manuele Michelessi, Jonathan Cook, Charles Boachie, Jennifer Burr, Katie Banister, David F. Garway-Heath, et al. "Diagnostic accuracy of optical coherence tomography for diagnosing glaucoma: secondary analyses of the GATE study." British Journal of Ophthalmology 102, no. 5 (August 30, 2017): 604–10. http://dx.doi.org/10.1136/bjophthalmol-2017-310642.

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Background/AimsTo assess the diagnostic performance of retinal nerve fibre layer (RNFL) data of optical coherence tomography (OCT) for detecting glaucoma.MethodsSecondary analyses of a prospective, multicentre diagnostic study (Glaucoma Automated Tests Evaluation (GATE)) referred to hospital eye services in the UK were conducted. We included data from 899 of 966 participants referred to hospital eye services with suspected glaucoma or ocular hypertension. We used both eyes’ data and logistic regression-based receiver operator characteristics analysis to build a set of models to measure the sensitivity and specificity of the average and inferior quadrant RNFL thickness data of OCT. The reference standard was expert clinician examination including automated perimetry. The main outcome measures were sensitivity at 0.95 specificity and specificity at 0.95 sensitivity and the corresponding RNFL thickness thresholds. We explored the possibility of accuracy improvement by adding measures of within-eye and between-eye variation, scan quality, intraocular pressure (IOP) and age.ResultsGlaucoma was diagnosed in at least one eye in 17% of participants. Areas under the curve were between 0.83 and 0.88. When specificity was fixed at 0.95, the sensitivity was between 0.38 and 0.55, and the highest values were reached with models including the inferior quadrant rather than the average RNFL thickness. Fixing sensitivity at 0.95, the specificity was between 0.36 and 0.58. The addition of age, refractive error, IOP or within-subject variation did not improve the accuracy.ConclusionRNFL thickness data of OCT can be used as a diagnostic test, but accuracy estimates remain moderate even in exploratory multivariable modelling of aiming to improve accuracy.

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Ustun, Teoman E., Nicusor V. Iftimia, R. Daniel Ferguson, and Daniel X. Hammer. "Real-time processing for Fourier domain optical coherence tomography using a field programmable gate array." Review of Scientific Instruments 79, no. 11 (November 2008): 114301. http://dx.doi.org/10.1063/1.3005996.

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Jang, Wonho, Koji Terashi, Masahiko Saito, Christian W. Bauer, Benjamin Nachman, Yutaro Iiyama, Tomoe Kishimoto, Ryunosuke Okubo, Ryu Sawada, and Junichi Tanaka. "Quantum Gate Pattern Recognition and Circuit Optimization for Scientific Applications." EPJ Web of Conferences 251 (2021): 03023. http://dx.doi.org/10.1051/epjconf/202125103023.

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There is no unique way to encode a quantum algorithm into a quantum circuit. With limited qubit counts, connectivities, and coherence times, circuit optimization is essential to make the best use of quantum devices produced over a next decade. We introduce two separate ideas for circuit optimization and combine them in a multi-tiered quantum circuit optimization protocol called AQCEL. The first ingredient is a technique to recognize repeated patterns of quantum gates, opening up the possibility of future hardware optimization. The second ingredient is an approach to reduce circuit complexity by identifying zero- or low-amplitude computational basis states and redundant gates. As a demonstration, AQCEL is deployed on an iterative and effcient quantum algorithm designed to model final state radiation in high energy physics. For this algorithm, our optimization scheme brings a significant reduction in the gate count without losing any accuracy compared to the original circuit. Additionally, we have investigated whether this can be demonstrated on a quantum computer using polynomial resources. Our technique is generic and can be useful for a wide variety of quantum algorithms.

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Kobr, Lukáš, Daniel M. Gardner, Amanda L. Smeigh, Scott M. Dyar, Steven D. Karlen, Raanan Carmieli, and Michael R. Wasielewski. "Fast Photodriven Electron Spin Coherence Transfer: A Quantum Gate Based on a Spin Exchange J-Jump." Journal of the American Chemical Society 134, no. 30 (July 24, 2012): 12430–33. http://dx.doi.org/10.1021/ja305650x.

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Vandamme, L. K. J., D. Rigaud, and J. M. Peransin. "Coherence between gate- and drain-current fluctuations in MESFET's and MODFET's biased in the ohmic region." IEEE Transactions on Electron Devices 39, no. 10 (1992): 2377–82. http://dx.doi.org/10.1109/16.158812.

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Mecê, Pedro, Kassandra Groux, Jules Scholler, Olivier Thouvenin, Mathias Fink, Kate Grieve, and Claude Boccara. "Coherence gate shaping for wide field high-resolution in vivo retinal imaging with full-field OCT." Biomedical Optics Express 11, no. 9 (August 7, 2020): 4928. http://dx.doi.org/10.1364/boe.400522.

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Qin, Peng, Hao Lu, Zhi Ye Jiang, Jin Liang Bai, Lu Gao, and Gang Meng. "Design and Test of High Speed Digitization Sampling Circuit Based on FPGA." Applied Mechanics and Materials 482 (December 2013): 386–89. http://dx.doi.org/10.4028/www.scientific.net/amm.482.386.

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To sample wideband IF signal with large amounts of data, a high-speed data acquisition program is presented. The program focus on circuit design, issues that need attention, and high-speed sampling signal deceleration strategy. The 2.4GHz rate sampling data acquisition, reception and demux are completed with ADC083000 and Field-Programmable Gate Array (FPGA). At last, a result of sampling with the converter is offered by chipscope software. The result verified ADC083000 has an excellent performance with more than 6.5 bit ENOB and good phase coherence. In engineering practice, the design has been used and has good performance.

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GHOSH, BAHNIMAN, J. SIVA CHANDRA, and AKSHAYKUMAR SALIMATH. "DESIGN OF A MULTI-LAYERED QCA CONFIGURABLE LOGIC BLOCK FOR FPGAs." Journal of Circuits, Systems and Computers 23, no. 06 (May 14, 2014): 1450089. http://dx.doi.org/10.1142/s0218126614500893.

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In this paper, a Multi-layered configurable logic block (CLB) unit for field programmable gate arrays (FPGAs) is proposed based on quantum-dot cellular automata (QCA) technology. The design is made in multiple layers which help to process information simultaneously, in different layers. Various components of CLB like (4 × 16) Decoder, Memory units, Multiplexers and RS-Flip flops are all designed in multiple layers using higher input majority gates to reduce the cell count and latency compared to previous designs. QCA Designer tool is used to design and simulate the model. The Coherence vector approximation is used for obtaining simulation results.

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WANG, ZHI-PING, and SHUANG-XI ZHANG. "ANALYSIS OF THE OPTICAL MULTISTABILITY BEHAVIOR IN A FOUR-LEVEL ATOMIC SYSTEM WITH AN ASSISTING MICROWAVE-DRIVEN FIELD." Modern Physics Letters B 24, no. 20 (August 10, 2010): 2151–60. http://dx.doi.org/10.1142/s0217984910024535.

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We show the steady-state optical multistability (OM) behavior in a four-level atomic system inside a unidirectional ring cavity. We find that the intensity and the detunings of the fields can affect the optical multistability behavior dramatically, which can be used to control the transition from OM to OB or vice versa without the need to resort to the effect of spontaneously generated coherence (SGC). The effect of the atomic cooperation parameter on OM is also studied. Our scheme may be used for building more efficient all-optical switches and logic-gate devices for optical computing and quantum information processing.

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Samartsev, V. V., D. I. Kamalova, and T. G. Mitrofanova. "Theoretical Study of the Possibility of Creating a Quantum Gate and Exciton Coherence on Semiconductor Quantum Dots." Bulletin of the Russian Academy of Sciences: Physics 82, no. 12 (December 2018): 1574–77. http://dx.doi.org/10.3103/s1062873818120195.

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Yousefjani, Rozhin, and Abolfazl Bayat. "Parallel entangling gate operations and two-way quantum communication in spin chains." Quantum 5 (May 26, 2021): 460. http://dx.doi.org/10.22331/q-2021-05-26-460.

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The power of a quantum circuit is determined through the number of two-qubit entangling gates that can be performed within the coherence time of the system. In the absence of parallel quantum gate operations, this would make the quantum simulators limited to shallow circuits. Here, we propose a protocol to parallelize the implementation of two-qubit entangling gates between multiple users which are spatially separated, and use a commonly shared spin chain data-bus. Our protocol works through inducing effective interaction between each pair of qubits without disturbing the others, therefore, it increases the rate of gate operations without creating crosstalk. This is achieved by tuning the Hamiltonian parameters appropriately, described in the form of two different strategies. The tuning of the parameters makes different bilocalized eigenstates responsible for the realization of the entangling gates between different pairs of distant qubits. Remarkably, the performance of our protocol is robust against increasing the length of the data-bus and the number of users. Moreover, we show that this protocol can tolerate various types of disorders and is applicable in the context of superconductor-based systems. The proposed protocol can serve for realizing two-way quantum communication.

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Stankovski, Tomislav, William H. Cooke, László Rudas, Aneta Stefanovska, and Dwain L. Eckberg. "Time-frequency methods and voluntary ramped-frequency breathing: a powerful combination for exploration of human neurophysiological mechanisms." Journal of Applied Physiology 115, no. 12 (December 15, 2013): 1806–21. http://dx.doi.org/10.1152/japplphysiol.00802.2013.

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We experimentally altered the timing of respiratory motoneuron activity as a means to modulate and better understand otherwise hidden human central neural and hemodynamic oscillatory mechanisms. We recorded the electrocardiogram, finger photoplethysmographic arterial pressure, tidal carbon dioxide concentrations, and muscle sympathetic nerve activity in 13 healthy supine young men who gradually increased or decreased their breathing frequencies between 0.05 and 0.25 Hz over 9-min periods. We analyzed results with traditional time- and frequency-domain methods, and also with time-frequency methods (wavelet transform, wavelet phase coherence, and directional coupling). We determined statistical significance and identified frequency boundaries by comparing measurements with randomly generated surrogates. Our results support several major conclusions. First, respiration causally modulates both sympathetic (weakly) and vagal motoneuron (strongly) oscillations over a wide frequency range—one that extends well below the frequency of actual breaths. Second, breathing frequency broadly modulates vagal baroreflex gain, with peak gains registered in the low frequency range. Third, breathing frequency does not influence median levels of sympathetic or vagal activity over time. Fourth, phase relations between arterial pressure and sympathetic and vagal motoneurons are unaffected by breathing, and are therefore likely secondary to intrinsic responsiveness of these motoneurons to other synaptic inputs. Finally, breathing frequency does not affect phase coherence between diastolic pressure and muscle sympathetic oscillations, but it augments phase coherence between systolic pressure and R-R interval oscillations over a limited portion of the usual breathing frequency range. These results refine understanding of autonomic oscillatory processes and those physiological mechanisms known as the human respiratory gate.

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Wan, Guo Chun, Meng Meng Li, He Xu, Wen Hao Kang, Jin Wen Rui, and Mei Song Tong. "XFinger-Net: Pixel-Wise Segmentation Method for Partially Defective Fingerprint Based on Attention Gates and U-Net." Sensors 20, no. 16 (August 10, 2020): 4473. http://dx.doi.org/10.3390/s20164473.

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Partially defective fingerprint image (PDFI) with poor performance poses challenges to the automated fingerprint identification system (AFIS). To improve the quality and the performance rate of PDFI, it is essential to use accurate segmentation. Currently, most fingerprint image segmentations use methods with ridge orientation, ridge frequency, coherence, variance, local gradient, etc. This paper proposes a method of XFinger-Net for segmenting PDFIs. Based on U-Net, XFinger-Net inherits its characteristics. The attention gate with fewer parameters is used to replace the cascaded network, which can suppress uncorrelated regions of PDFIs. Moreover, the XFinger-Net implements a pixel-level segmentation and takes non-blocking fingerprint images as an input to preserve the global characteristics of PDFIs. The XFinger-Net can achieve a very good segmentation effect as demonstrated in the self-made fingerprint segmentation test.

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Li, Kai, and Qing-yu Cai. "Practical Security of RSA Against NTC-Architecture Quantum Computing Attacks." International Journal of Theoretical Physics 60, no. 8 (June 19, 2021): 2733–44. http://dx.doi.org/10.1007/s10773-021-04789-x.

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AbstractQuantum algorithms can greatly speed up computation in solving some classical problems, while the computational power of quantum computers should also be restricted by laws of physics. Due to quantum time-energy uncertainty relation, there is a lower limit of the evolution time for a given quantum operation, and therefore the time complexity must be considered when the number of serial quantum operations is particularly large. When the key length is about at the level of KB (encryption and decryption can be completed in a few minutes by using standard programs), it will take at least 50-100 years for NTC (Neighbor-only, Two-qubit gate, Concurrent) architecture ion-trap quantum computers to execute Shor’s algorithm. For NTC architecture superconducting quantum computers with a code distance 27 for error-correcting, when the key length increased to 16 KB, the cracking time will also increase to 100 years that far exceeds the coherence time. This shows the robustness of the updated RSA against practical quantum computing attacks.

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Khudhur, Ahmed Mahmood, Ahmed N. Abdalla, Jasni Mohamad Zain, and Hai Tao. "An investigation of the coefficient of variation using voltage clamps techniques." International Journal of Basic and Applied Sciences 4, no. 4 (October 17, 2015): 364. http://dx.doi.org/10.14419/ijbas.v4i4.5049.

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<p class="MsoNormal" style="text-align: justify; text-justify: inter-ideograph;"><span style="font-size: 10.0pt;">In recent years, it has been argued and experimentally shown that ion channel noise in neurons can have profound effects on the neuron’s dynamical behavior. Most profoundly, ion channel noise was seen to be able to cause spontaneous firing and stochastic resonance. It has been recently found that a non-trivially persistent cross correlation takes place between the transmembrane voltage fluctuations and the component of open channel fluctuations attributed to gate multiplicity. This non-trivial phenomenon was found to play a major augmentative role for the elevation of excitability and spontaneous firing in the small size cell. In addition, the same phenomenon was found to significantly enhance the spike coherence. In this paper, statistics of the coefficient of variation, to be obtained from the colored stochastic Hodgkin-Huxley equations using voltage clamps techniqueswill be studied. The simulation result shows the coefficient of variation; enhance the agreement with the microscopeinthe case of the noisy currents.</span></p>

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Henriet, Loïc, Lucas Beguin, Adrien Signoles, Thierry Lahaye, Antoine Browaeys, Georges-Olivier Reymond, and Christophe Jurczak. "Quantum computing with neutral atoms." Quantum 4 (September 21, 2020): 327. http://dx.doi.org/10.22331/q-2020-09-21-327.

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The manipulation of neutral atoms by light is at the heart of countless scientific discoveries in the field of quantum physics in the last three decades. The level of control that has been achieved at the single particle level within arrays of optical traps, while preserving the fundamental properties of quantum matter (coherence, entanglement, superposition), makes these technologies prime candidates to implement disruptive computation paradigms. In this paper, we review the main characteristics of these devices from atoms / qubits to application interfaces, and propose a classification of a wide variety of tasks that can already be addressed in a computationally efficient manner in the Noisy Intermediate Scale Quantum\cite{Preskill_NISQ} era we are in. We illustrate how applications ranging from optimization challenges to simulation of quantum systems can be explored either at the digital level (programming gate-based circuits) or at the analog level (programming Hamiltonian sequences). We give evidence of the intrinsic scalability of neutral atom quantum processors in the 100-1,000 qubits range and introduce prospects for universal fault tolerant quantum computing and applications beyond quantum computing.

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Gül, Yusuf. "On-chip photonic transistor based on the spike synchronization in circuit QED." International Journal of Modern Physics B 32, no. 08 (March 13, 2018): 1850088. http://dx.doi.org/10.1142/s0217979218500881.

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We consider the single photon transistor in coupled cavity system of resonators interacting with multilevel superconducting artificial atom simultaneously. Effective single mode transformation is used for the diagonalization of the Hamiltonian and impedance matching in terms of the normal modes. Storage and transmission of the incident field are described by the interactions between the cavities controlling the atomic transitions of lowest lying states. Rabi splitting of vacuum-induced multiphoton transitions is considered in input/output relations by the quadrature operators in the absence of the input field. Second-order coherence functions are employed to investigate the photon blockade and delocalization–localization transitions of cavity fields. Spontaneous virtual photon conversion into real photons is investigated in localized and oscillating regimes. Reflection and transmission of cavity output fields are investigated in the presence of the multilevel transitions. Accumulation and firing of the reflected and transmitted fields are used to investigate the synchronization of the bunching spike train of transmitted field and population imbalance of cavity fields. In the presence of single photon gate field, gain enhancement is explained for transmitted regime.

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Biercuk, M. J., H. Uys, A. P. VanDevender, N. Shiga, W. M. Itano, and J. J. Bollinger. "High-fidelity quantum control using ion crystals in a Penning trap." Quantum Information and Computation 9, no. 11&12 (November 2009): 920–49. http://dx.doi.org/10.26421/qic9.11-12-2.

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We provide an introduction to the use of ion crystals in a Penning trap for experiments in quantum information. Macroscopic Penning traps allow for the containment of a few to a few million atomic ions whose internal states may be used in quantum information experiments. Ions are laser Doppler cooled, and the mutual Coulomb repulsion of the ions leads to the formation of crystalline arrays. The structure and dimensionality of the resulting ion crystals may be tuned using a combination of control laser beams and external potentials. We discuss the use of two-dimensional $^{9}$Be$^{+}$ ion crystals for experimental tests of quantum control techniques. Our primary qubit is the 124 GHz ground-state electron spin flip transition, which we drive using microwaves. An ion crystal represents a spatial ensemble of qubits, but the effects of inhomogeneities across a typical crystal are small, and as such we treat the ensemble as a single effective spin. We are able to initialize the qubits in a simple state and perform a projective measurement on the system. We demonstrate full control of the qubit Bloch vector, performing arbitrary high-fidelity rotations ($\tau_{\pi}\sim$200 $\mu$s). Randomized Benchmarking demonstrates an error per gate (a Pauli-randomized $\pi/2$ and $\pi$ pulse pair) of $8\pm1\times10^{-4}$. Ramsey interferometry and spin-locking measurements are used to elucidate the limits of qubit coherence in the system, yielding a typical free-induction decay coherence time of $T_{2}\sim$2 ms, and a limiting $T_{1\rho}\sim$688 ms. These experimental specifications make ion crystals in a Penning trap ideal candidates for novel experiments in quantum control. As such, we briefly describe recent efforts aimed at studying the error-suppressing capabilities of dynamical decoupling pulse sequences, demonstrating an ability to extend qubit coherence and suppress phase errors. We conclude with a discussion of future avenues for experimental exploration, including the use of additional nuclear-spin-flip transitions for effective multiqubit protocols, and the potential for Coulomb crystals to form a useful testbed for studies of large-scale entanglement.

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Lyu, Yan, Huaxing Hong, Guorong Song, and Cunfu He. "A Simplified Integration of Multi-Channel Ultrasonic Guided Wave System for Phased Array Detection and Total Focusing Imaging." International Journal of Acoustics and Vibration 26, no. 2 (June 30, 2021): 104–9. http://dx.doi.org/10.20855/ijav.2021.26.21695.

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Ultrasonic guided waves based on sensors array effectively improve the detection sensitivity of defects and realize the intuitive imaging of defects. In this research, a 16-channel guided wave excitation/acquisition system is simply integrated for the array focusing detection. Using a FPGA (Field Programmable Gate Array) as the main control unit, a high-voltage excitation of a multi-channel tone-burst signal with synchronous signal acquisition is designed. Experiments are conducted by the developed multi-channel system and the piezoelectric linear array. A guided wave phased array and the total focusing imaging algorithm are demonstrated on a 1mm aluminum plate. The experimental results show that the system can meet the practical requirements of guided wave array focusing detection. By combining the total focusing method and the phase-based sign coherence factor, the compounded image shows that the artifacts can effectively be reduced, and the contrast is improved. Meanwhile, this system can solve the problem of distributed sensor array detection, in which the process is cumbersome and inefficient previously. Through the system and the sensor array, the guided wave phased focusing method and the composite total focusing method can effectively improve the sensitivity and the positioning accuracy of defect detection in thin plate.

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Kielpinski, D., A. Ben-Kish, J. Britton, V. Meyer, M. A. Rowe, W. M. Itano, D. J. Wineland, C. Sackett, and C. Monroe. "Recent results in trapped-ion quantum computing at NIST." Quantum Information and Computation 1, Special (December 2001): 113–23. http://dx.doi.org/10.26421/qic1.s-12.

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We review recent experiments on entanglement, Bell's inequality, and decoherence-free subspaces in a quantum register of trapped {9Be+} ions. We have demonstrated entanglement of up to four ions using the technique of Molmer and Sorensen. This method produces the state ({|\uparrow\uparrow\rangle}+{|\downarrow\downarrow\rangle})/\sqrt{2} for two ions and the state ({\downarrow}{\downarrow}{\downarrow}{\downarrow} \rangle + | {\uparrow}{\uparrow}{\uparrow}{\uparrow} \rangle)/\sqrt{2} for four ions. We generate the entanglement deterministically in each shot of the experiment. Measurements on the two-ion entangled state violates Bell's inequality at the 8\sigma level. Because of the high detector efficiency of our apparatus, this experiment closes the detector loophole for Bell's inequality measurements for the first time. This measurement is also the first violation of Bell's inequality by massive particles that does not implicitly assume results from quantum mechanics. Finally, we have demonstrated reversible encoding of an arbitrary qubit, originally contained in one ion, into a decoherence-free subspace (DFS) of two ions. The DFS-encoded qubit resists applied collective dephasing noise and retains coherence under ambient conditions 3.6 times longer than does an unencoded qubit. The encoding method, which uses single-ion gates and the two-ion entangling gate, demonstrates all the elements required for two-qubit universal quantum logic.

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Kalmpourtzis, George, and Margarida Romero. "Constructive alignment of learning mechanics and game mechanics in Serious Game design in Higher Education." International Journal of Serious Games 7, no. 4 (December 4, 2020): 75–88. http://dx.doi.org/10.17083/ijsg.v7i4.361.

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Game design is a complex process based on balance between educational and gameplay experience in a coherent way. In the context of instructional design, Constructive Alignment aims to develop an outcome-based approach for designing learning activities during which the learners’ engagement through the activity is aligned with learning objectives and outcomes. Constructive Alignment focuses on the proposal of constructively aligned learning experiences, where assessment is the result of specially selected training activities, which are proposed based on intended learning outcomes. In this study, we analyze the game design process in an online master course on Game Design from a Constructive Alignment approach. We operationalize the Constructive Alignment in game design as the coherence between Learning Objectives, Game Mechanics, Learning Mechanics and the Assessment in the educational DGBL. The results analysis shows that the Game Based Learning course had a positive impact on students regarding the proposal of game design documents with coherence between Game Mechanics and Learning Mechanics as well as Learning Mechanics and Learning Objectives, while little focus on integrating Assessment mechanisms was observed. Based on the results of this study we propose to increase the focus on assessment in the process of game design.

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Hill, Charles D., Eldad Peretz, Samuel J. Hile, Matthew G. House, Martin Fuechsle, Sven Rogge, Michelle Y. Simmons, and Lloyd C. L. Hollenberg. "A surface code quantum computer in silicon." Science Advances 1, no. 9 (October 2015): e1500707. http://dx.doi.org/10.1126/sciadv.1500707.

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The exceptionally long quantum coherence times of phosphorus donor nuclear spin qubits in silicon, coupled with the proven scalability of silicon-based nano-electronics, make them attractive candidates for large-scale quantum computing. However, the high threshold of topological quantum error correction can only be captured in a two-dimensional array of qubits operating synchronously and in parallel—posing formidable fabrication and control challenges. We present an architecture that addresses these problems through a novel shared-control paradigm that is particularly suited to the natural uniformity of the phosphorus donor nuclear spin qubit states and electronic confinement. The architecture comprises a two-dimensional lattice of donor qubits sandwiched between two vertically separated control layers forming a mutually perpendicular crisscross gate array. Shared-control lines facilitate loading/unloading of single electrons to specific donors, thereby activating multiple qubits in parallel across the array on which the required operations for surface code quantum error correction are carried out by global spin control. The complexities of independent qubit control, wave function engineering, and ad hoc quantum interconnects are explicitly avoided. With many of the basic elements of fabrication and control based on demonstrated techniques and with simulated quantum operation below the surface code error threshold, the architecture represents a new pathway for large-scale quantum information processing in silicon and potentially in other qubit systems where uniformity can be exploited.

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Cannon, Jonathan. "Analytical Calculation of Mutual Information between Weakly Coupled Poisson-Spiking Neurons in Models of Dynamically Gated Communication." Neural Computation 29, no. 1 (January 2017): 118–45. http://dx.doi.org/10.1162/neco_a_00915.

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Mutual information is a commonly used measure of communication between neurons, but little theory exists describing the relationship between mutual information and the parameters of the underlying neuronal interaction. Such a theory could help us understand how specific physiological changes affect the capacity of neurons to synaptically communicate, and, in particular, they could help us characterize the mechanisms by which neuronal dynamics gate the flow of information in the brain. Here we study a pair of linear-nonlinear-Poisson neurons coupled by a weak synapse. We derive an analytical expression describing the mutual information between their spike trains in terms of synapse strength, neuronal activation function, the time course of postsynaptic currents, and the time course of the background input received by the two neurons. This expression allows mutual information calculations that would otherwise be computationally intractable. We use this expression to analytically explore the interaction of excitation, information transmission, and the convexity of the activation function. Then, using this expression to quantify mutual information in simulations, we illustrate the information-gating effects of neural oscillations and oscillatory coherence, which may either increase or decrease the mutual information across the synapse depending on parameters. Finally, we show analytically that our results can quantitatively describe the selection of one information pathway over another when multiple sending neurons project weakly to a single receiving neuron.

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King, Andrew, and Xun Luo. "Methodology for tomographic imaging ahead of mining using the shearer as a seismic source." GEOPHYSICS 74, no. 2 (March 2009): M1—M8. http://dx.doi.org/10.1190/1.3074334.

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Poor rock conditions in a coal longwall panel can result in roof collapse when a problematic zone is mined, significantly interrupting mine production. The ability to image rock conditions — stress and degree of fracturing — ahead of the face gives the miners the ability to respond proactively to such problems. This method uses the energy from mining machinery, in this case a coal shearer, to produce an image of the rock velocity ahead of the mining face without interrupting mining. Data from an experiment illustrates the concept. Geophones installed in gate-road roofs record the noise generated by the shearer after it has traversed the panel ahead of the mining face. A generalized crosscorrelation of the signals from pairs of sensors determines relative arrival times from the continuous seismic noise produced by the shearer. These relative times can then be inverted for a velocity structure. The crosscorrelations, performed in the frequency domain, are weighted by a confidence value derived from the spectral coherence between the traces. This produces stable crosscorrelation lags in the presence of noise. The errors in the time-domain data are propagated through to the relative traveltimes and then to the final tomographic velocity image, yielding an estimate of the uncertainty in velocity at each point. This velocity image can then be used to infer information about the stress and fracture state of the rock, providing advance warning of potentially hazardous zones.

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Journal articles on the topic 'Coherence gate'

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