DOCSLIB.ORG

Perception of Visual Motion Coherence by Rats and Mice

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Perception of Visual Motion Coherence by Rats and Mice View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Elsevier - Publisher Connector Vision Research 46 (2006) 2842–2847 www.elsevier.com/locate/visres Perception of visual motion coherence by rats and mice R.M. Douglas a,b,¤, A. Neve b, J.P. Quittenbaum b, N.M. Alam a, G.T. Prusky b a Department of Ophthalmology and Visual Sciences, University of British Columbia, 2550 Willow Street, Vancouver, BC, Canada V5Z 3N9 b Canadian Centre for Behavioural Neuroscience, The University of Lethbridge, 4401 University Drive, Lethbridge, Alta., Canada T1K 3M4 Received 13 November 2004; received in revised form 17 January 2006 Abstract The coherence thresholds to discriminate the direction of motion in random-dot kinematograms were measured in rats and mice. Per- formance was best in the rats when dot displacement from frame-to-frame was about 2 degrees, and frame duration was less than 100 ms. Mice had coherence thresholds similar to those of rats when tested at the same step size and frame duration. Although the lowest thresh- olds in the rats and mice occasionally reached human levels, average rodent values (»25%) were 2–3 times higher than those of humans. These data indicate that the rodent and primate visual systems are similar in that both have local motion detectors and a system for extracting global motion from a noisy signal. © 2006 Elsevier Ltd. All rights reserved. Keywords: Extrastriate cortex; MT; Random dot; Kinematograms; Visual water task; Psychophysics 1. Introduction is, however, an open question whether primates have unique cortical capabilities, or whether such a functional The detection and eVective use of visual motion is organization is a fundamental property of mammalian widespread in the animal kingdom. Experimental investi- visual systems. If extrastriate analysis of global visual gations of the neural mechanisms of motion perception motion is common to mammals, this would have implica- have been conducted in species as diverse as Xies, pigeons, tions for its evolution and ecological utility. In addition, and monkeys (CliVord & Ibbotson, 2002), and simple studying motion perception in laboratory rodents would neural circuits capable of detecting local motion of single facilitate experiments into the cellular and molecular elements have been studied in the Xy (Reichardt, 1961) substrates of visual motion processing. To this point, and rabbit retinas (Barlow & Levick, 1965; Fried, Munch, however, no systematic study of motion perception has & Werblin, 2002). In recent years, it has become common been conducted in rodents, largely because it has been too to use dynamically moving random-dot patterns (or diYcult to test their visual motion thresholds psycho- kinematograms) to assess visual motion, as they enable physically. Over the past several years, we have used the the study of motion perception in the absence of posi- Visual Water Task (Prusky, West, & Douglas, 2000) to tional or form cues (Nakayama & Tyler, 1981). Percep- quantify acuity and contrast sensitivity thresholds in rats tual mechanisms that can detect common motion of and mice (McGill, Douglas, Lund, & Prusky, 2004; Pru- many elements have been identiWed in humans and other sky et al., 2000; Prusky & Douglas, 2004), and we report primates (Braddick, 1974; Morgan & Ward, 1980; Wil- here that this task can be adapted to measure their visual liams & Sekuler, 1984) and localized to extrastriate cor- motion thresholds. tex (Baker, Hess, & Zihl, 1991; Newsome & Paré, 1988). It In order to determine whether rodents have visual motion capabilities and anatomical substrates comparable * Corresponding author. Fax: +1 604 876 6553. to primates, we compared the dot motion coherence thresh- E-mail address: [email protected] (R.M. Douglas). olds of rats with those of humans. 0042-6989/$ - see front matter © 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.visres.2006.02.025 R.M. Douglas et al. / Vision Research 46 (2006) 2842–2847 2843 2. Methods 2.3. Stimuli 2.1. Subjects Kinematograms were computed separately for each monitor before every trial, and were then played continuously until the end of the trial. A Six adult female Long–Evans rats and six adult C57BL/6 mice were random-dot kinematogram consisted of 24 frames or images. The diame- used in the experiments. The animals were between 90 and 150 days of age ter of the round dots was 1.9° for the rats, and 2.9° for the mice as studies at the start of training, and testing continued over the subsequent 4–6 from our laboratory (e.g., Prusky et al., 2000) have shown that the grating months. All procedures were authorized by the University of Lethbridge acuities of Long–Evans rats and C57BL/6 mice are 1.0 and 0.55 cycles per Animal Care Committee, which approves procedures that are conducted degree (c/d), respectively. The total area of the dots was about 20% of the in accordance with the standards of the Canadian Council on Animal screen area, and this corresponded to there being 62 (rats) or 28 (mice) 2 Care. dots on each image frame. The dots had a luminance of 96 cd/m and the 2 To facilitate comparison with human motion vision, three human background was 1.1 cd/m . observers viewed the same stimuli from the same distance. They used Each dot could move from one frame to the next, or disappear. The pushbuttons to start each trial and to record their decisions about which step size, or amplitude of the displacements from fame to frame, was the side had the positive stimulus. Human testing was conducted in accor- same for all dots, with only the direction of movement varied between dance with the guidelines of the University of Lethbridge Human Subjects frames. Motion noise was introduced by having a percentage of the dots Research Committee. move in random directions (Fig. 2) with the additional constraint that there was no net movement. The remainder of the dots all moved in one, 2.2. Apparatus coherent direction. Dot displacements of 0.24°, 0.47°, 0.94°, 1.88°, 3.77°, 5.65°, and 7.54° were used in diVerent blocks of trials. The Visual Water Task (Prusky et al., 2000) uses a trapezoidal tank After moving for 2 or 12 frames (lifetime) each dot was randomly repo- (120 cm L £ 80 cm W £ 26 cm W £ 55 cm H) with two ViewSonic EF70, sitioned, thus ensuring a constant number of dots on screen. A constant 17Љ computer monitors facing into one end (Fig. 1). A midline divider percent of dots died and were reborn elsewhere on each frame, and motion (46 cm) extends into the pool from between the monitors, each of which wrapped from the 24th to the 1st frame so that the kinematogram could be subtended about 30° degrees when viewed from the end of the divider. The played continuously. Longer lifetimes were not possible with a looping tank was Wlled with water, and an escape platform was placed just below requirement, and thus dot lifetimes of 2 and 12 frames limited the maxi- V the surface directly under one of the monitors. The platform was always mum e ective coherence to 50 and 92%, respectively (Bischof, Reid, Wylie, located below the positive (+; reinforced) stimulus. Visual stimuli were & Spetch, 1999). generated by, and the experiments were controlled with custom software. Frame duration set the stimulus onset asynchrony (SOA) for the dots to appear on two successive frames, and frame duration was a multiple of the video screen refresh rate. In the experiments with rats, 1, 2, 4, 8, 13, 19, and 26 screen refreshes were employed. As the monitors had an 85 Hz ver- tical refresh rate, these values translate to frame durations of 12, 24, 48, 94, 153, 224, and 306 ms. Video – + Monitors 2.4. Behavioral testing The animals were trained to associate swimming to the positive stimu- Submerged lus, regardless of its left/right location, with escape from water. The initial Platform training consisted of training the rat or mouse to distinguish between 100 and 0% coherence. Rats learned to grasp the end of the divider and inspect both screens before making a choice; mice tended to slow down at the bar- rier and swim back and forth before making a choice. After an animal had Wnished a trial, it was returned to a holding box to dry and groom while the other 5 animals completed the same trial. Sessions consisted of 15–20 Choice trials per animal. The training kinematograms had a step size of 0.471°, a Plane frame duration of 12 ms, and a lifetime of 10 frames. Once the rats reached at least 80% accuracy over a block of 10 trials, we changed the task to identifying the direction of motion. This had the advantage that the kinematograms on the two monitors were identical in coherence, step size, frame duration, and lifetime, and only diVered in Water 0% Coherence 100% Coherence Start Point Fig. 1. Schematic top-view of the Visual Water Task. The task uses a trape- zoidal pool with two computer monitors at one end displaying either a pos- Fig. 2. Schematic diagram of stimulus attributes. Motion coherence dis- itive (+, reinforced) or negative (¡, non-reinforced) stimulus. An escape plays consisted of multiple dots that could move in any direction across platform is placed below the monitor showing the positive stimulus and the frames. After moving on 2 or 12 successive frames, the dot disappeared left/right position of the pair is randomized. The platform surface is just and a new dot was created at another random location on the screen below the water level and is not visible to the animal. Animals are released (dashed circles).
Load more

Recommended publications
  • The Theory of Quantum Coherence María García Díaz
    ADVERTIMENT. Lʼaccés als continguts dʼaquesta tesi queda condicionat a lʼacceptació de les condicions dʼús establertes per la següent llicència Creative Commons: http://cat.creativecommons.org/?page_id=184 ADVERTENCIA. El acceso a los contenidos de esta tesis queda condicionado a la aceptación de las condiciones de uso establecidas por la siguiente licencia Creative Commons: http://es.creativecommons.org/blog/licencias/ WARNING. The access to the contents of this doctoral thesis it is limited to the acceptance of the use conditions set by the following Creative Commons license: https://creativecommons.org/licenses/?lang=en Universitat Aut`onomade Barcelona The theory of quantum coherence by Mar´ıaGarc´ıaD´ıaz under supervision of Prof. Andreas Winter A thesis submitted in partial fulfillment for the degree of Doctor of Philosophy in Unitat de F´ısicaTe`orica:Informaci´oi Fen`omensQu`antics Departament de F´ısica Facultat de Ci`encies Bellaterra, December, 2019 “The arts and the sciences all draw together as the analyst breaks them down into their smallest pieces: at the hypothetical limit, at the very quick of epistemology, there is convergence of speech, picture, song, and instigating force.” Daniel Albright, Quantum poetics: Yeats, Pound, Eliot, and the science of modernism Abstract Quantum coherence, or the property of systems which are in a superpo- sition of states yielding interference patterns in suitable experiments, is the main hallmark of departure of quantum mechanics from classical physics. Besides its fascinating epistemological implications, quantum coherence also turns out to be a valuable resource for quantum information tasks, and has even been used in the description of fundamental biological processes.
    [Show full text]
  • Path Integrals in Quantum Mechanics
    Path Integrals in Quantum Mechanics Dennis V. Perepelitsa MIT Department of Physics 70 Amherst Ave. Cambridge, MA 02142 Abstract We present the path integral formulation of quantum mechanics and demon- strate its equivalence to the Schr¨odinger picture. We apply the method to the free particle and quantum harmonic oscillator, investigate the Euclidean path integral, and discuss other applications. 1 Introduction A fundamental question in quantum mechanics is how does the state of a particle evolve with time? That is, the determination the time-evolution ψ(t) of some initial | i state ψ(t ) . Quantum mechanics is fully predictive [3] in the sense that initial | 0 i conditions and knowledge of the potential occupied by the particle is enough to fully specify the state of the particle for all future times.1 In the early twentieth century, Erwin Schr¨odinger derived an equation specifies how the instantaneous change in the wavefunction d ψ(t) depends on the system dt | i inhabited by the state in the form of the Hamiltonian. In this formulation, the eigenstates of the Hamiltonian play an important role, since their time-evolution is easy to calculate (i.e. they are stationary). A well-established method of solution, after the entire eigenspectrum of Hˆ is known, is to decompose the initial state into this eigenbasis, apply time evolution to each and then reassemble the eigenstates. That is, 1In the analysis below, we consider only the position of a particle, and not any other quantum property such as spin. 2 D.V. Perepelitsa n=∞ ψ(t) = exp [ iE t/~] n ψ(t ) n (1) | i − n h | 0 i| i n=0 X This (Hamiltonian) formulation works in many cases.
    [Show full text]
  • Optimization of Transmon Design for Longer Coherence Time
    Optimization of transmon design for longer coherence time Simon Burkhard Semester thesis Spring semester 2012 Supervisor: Dr. Arkady Fedorov ETH Zurich Quantum Device Lab Prof. Dr. A. Wallraff Abstract Using electrostatic simulations, a transmon qubit with new shape and a large geometrical size was designed. The coherence time of the qubits was increased by a factor of 3-4 to about 4 µs. Additionally, a new formula for calculating the coupling strength of the qubit to a transmission line resonator was obtained, allowing reasonably accurate tuning of qubit parameters prior to production using electrostatic simulations. 2 Contents 1 Introduction 4 2 Theory 5 2.1 Coplanar waveguide resonator . 5 2.1.1 Quantum mechanical treatment . 5 2.2 Superconducting qubits . 5 2.2.1 Cooper pair box . 6 2.2.2 Transmon . 7 2.3 Resonator-qubit coupling (Jaynes-Cummings model) . 9 2.4 Effective transmon network . 9 2.4.1 Calculation of CΣ ............................... 10 2.4.2 Calculation of β ............................... 10 2.4.3 Qubits coupled to 2 resonators . 11 2.4.4 Charge line and flux line couplings . 11 2.5 Transmon relaxation time (T1) ........................... 11 3 Transmon simulation 12 3.1 Ansoft Maxwell . 12 3.1.1 Convergence of simulations . 13 3.1.2 Field integral . 13 3.2 Optimization of transmon parameters . 14 3.3 Intermediate transmon design . 15 3.4 Final transmon design . 15 3.5 Comparison of the surface electric field . 17 3.6 Simple estimate of T1 due to coupling to the charge line . 17 3.7 Simulation of the magnetic flux through the split junction .
    [Show full text]
  • On Coherence and the Transverse Spatial Extent of a Neutron Wave Packet
    On coherence and the transverse spatial extent of a neutron wave packet C.F. Majkrzak, N.F. Berk, B.B. Maranville, J.A. Dura, Center for Neutron Research, and T. Jach Materials Measurement Laboratory, National Institute of Standards and Technology Gaithersburg, MD 20899 (18 November 2019) Abstract In the analysis of neutron scattering measurements of condensed matter structure, it normally suffices to treat the incident and scattered neutron beams as if composed of incoherent distributions of plane waves with wavevectors of different magnitudes and directions which are taken to define an instrumental resolution. However, despite the wide-ranging applicability of this conventional treatment, there are cases in which the wave function of an individual neutron in the beam must be described more accurately by a spatially localized packet, in particular with respect to its transverse extent normal to its mean direction of propagation. One such case involves the creation of orbital angular momentum (OAM) states in a neutron via interaction with a material device of a given size. It is shown in the work reported here that there exist two distinct measures of coherence of special significance and utility for describing neutron beams in scattering studies of materials in general. One measure corresponds to the coherent superposition of basis functions and their wavevectors which constitute each individual neutron packet state function whereas the other measure can be associated with an incoherent distribution of mean wavevectors of the individual neutron packets in a beam. Both the distribution of the mean wavevectors of individual packets in the beam as well as the wavevector components of the superposition of basis functions within an individual packet can contribute to the conventional notion of instrumental resolution.
    [Show full text]
  • Partial Coherence Effects on the Imaging of Small Crystals Using Coherent X-Ray Diffraction
    INSTITUTE OF PHYSICS PUBLISHING JOURNAL OF PHYSICS: CONDENSED MATTER J. Phys.: Condens. Matter 13 (2001) 10593–10611 PII: S0953-8984(01)25635-5 Partial coherence effects on the imaging of small crystals using coherent x-ray diffraction I A Vartanyants1 and I K Robinson Department of Physics, University of Illinois, 1110 West Green Street, Urbana, IL 61801, USA Received 8 June 2001 Published 9 November 2001 Online at stacks.iop.org/JPhysCM/13/10593 Abstract Recent achievements in experimental and computational methods have opened up the possibility of measuring and inverting the diffraction pattern from a single-crystalline particle on the nanometre scale. In this paper, a theoretical approach to the scattering of purely coherent and partially coherent x-ray radiation by such particles is discussed in detail. Test calculations based on the iterative algorithms proposed initially by Gerchberg and Saxton and generalized by Fienup are applied to reconstruct the shape of the scattering crystals. It is demonstrated that partially coherent radiation produces a small area of high intensity in the reconstructed image of the particle. (Some figures in this article are in colour only in the electronic version) 1. Introduction Even in the early years of x-ray studies [1–4] it was already understood that the diffraction pattern from small perfect crystals is directly connected with the shape of these crystals through Fourier transformation. Of course, in a real diffraction experiment on a ‘powder’ sample, where many particles with different shapes and orientations are illuminated by an incoherent beam, only an averaged shape of these particles can be obtained.
    [Show full text]
  • Less Decoherence and More Coherence in Quantum Gravity, Inflationary Cosmology and Elsewhere
    Less Decoherence and More Coherence in Quantum Gravity, Inflationary Cosmology and Elsewhere Elias Okon1 and Daniel Sudarsky2 1Instituto de Investigaciones Filosóficas, Universidad Nacional Autónoma de México, Mexico City, Mexico. 2Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Mexico City, Mexico. Abstract: In [1] it is argued that, in order to confront outstanding problems in cosmol- ogy and quantum gravity, interpretational aspects of quantum theory can by bypassed because decoherence is able to resolve them. As a result, [1] concludes that our focus on conceptual and interpretational issues, while dealing with such matters in [2], is avoidable and even pernicious. Here we will defend our position by showing in detail why decoherence does not help in the resolution of foundational questions in quantum mechanics, such as the measurement problem or the emergence of classicality. 1 Introduction Since its inception, more than 90 years ago, quantum theory has been a source of heated debates in relation to interpretational and conceptual matters. The prominent exchanges between Einstein and Bohr are excellent examples in that regard. An avoid- ance of such issues is often justified by the enormous success the theory has enjoyed in applications, ranging from particle physics to condensed matter. However, as people like John S. Bell showed [3], such a pragmatic attitude is not always acceptable. In [2] we argue that the standard interpretation of quantum mechanics is inadequate in cosmological contexts because it crucially depends on the existence of observers external to the studied system (or on an artificial quantum/classical cut). We claim that if the system in question is the whole universe, such observers are nowhere to be found, so we conclude that, in order to legitimately apply quantum mechanics in such contexts, an observer independent interpretation of the theory is required.
    [Show full text]
  • Lecture 21 (Interference III Thin Film Interference and the Michelson Interferometer) Physics 2310-01 Spring 2020 Douglas Fields Thin Films
    Lecture 21 (Interference III Thin Film Interference and the Michelson Interferometer) Physics 2310-01 Spring 2020 Douglas Fields Thin Films • We are all relatively familiar with the phenomena of thin film interference. • We’ve seen it in an oil slick or in a soap bubble. "Dieselrainbow" by John. Licensed under CC BY-SA 2.5 via Commons - • But how is this https://commons.wikimedia.org/wiki/File:Dieselrainbow.jpg#/media/File:Diesel rainbow.jpg interference? • What are the two sources? • Why are there colors instead of bright and dark spots? "Thinfilmbubble" by Threetwoone at English Wikipedia - Transferred from en.wikipedia to Commons.. Licensed under CC BY 2.5 via Commons - https://commons.wikimedia.org/wiki/File:Thinfilmbubble.jpg#/media/File:Thinfilmb ubble.jpg The two sources… • In thin film interference, the two sources of coherent light come from reflections from two different interfaces. • Different geometries will provide different types of interference patterns. • The “thin film” could just be an air gap, for instance. Coherence and Thin Film Interference • Why “thin film”? • Generally, when talking about thin film interference, the source light is what we would normally call incoherent – sunlight or room light. • However, most light is coherent on a small enough distance/time scale… • The book describes it like this: Coherence - Wikipedia • Perfectly coherent: "Single frequency correlation" by Glosser.ca - Own work. Licensed under CC BY-SA 4.0 via Commons - https://commons.wikimedia.org/wiki/File:Single_frequency_correlation.svg#/media/File:Single_frequency_correlation.svg • Spatially partially coherent: "Spatial coherence finite" by Original uploader was J S Lundeen at en.wikipedia - Transferred from en.wikipedia; transferred to Commons by User:Shizhao using CommonsHelper.
    [Show full text]
  • Uncertainty Relations for Quantum Coherence
    Article Uncertainty Relations for Quantum Coherence Uttam Singh 1,*, Arun Kumar Pati 1 and Manabendra Nath Bera 2 1 Harish-Chandra Research Institute, Chhatnag Road, Jhunsi, Allahabad 211 019, India; [email protected] 2 ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology, ES-08860 Castelldefels, Spain; [email protected] * Correspondence: [email protected]; Tel.: +91-532-2274-407; Fax: +91-532-2567-748 Academic Editors: Paul Busch, Takayuki Miyadera and Teiko Heinosaari Received: 4 April 2016; Accepted: 9 July 2016; Published: 16 July 2016 Abstract: Coherence of a quantum state intrinsically depends on the choice of the reference basis. A natural question to ask is the following: if we use two or more incompatible reference bases, can there be some trade-off relation between the coherence measures in different reference bases? We show that the quantum coherence of a state as quantified by the relative entropy of coherence in two or more noncommuting reference bases respects uncertainty like relations for a given state of single and bipartite quantum systems. In the case of bipartite systems, we find that the presence of entanglement may tighten the above relation. Further, we find an upper bound on the sum of the relative entropies of coherence of bipartite quantum states in two noncommuting reference bases. Moreover, we provide an upper bound on the absolute value of the difference of the relative entropies of coherence calculated with respect to two incompatible bases. Keywords: uncertainty relations; coherence; quantum correlations 1. Introduction The linearity of quantum mechanics gives rise to the concept of superposition of quantum states of a quantum system and is one of the characteristic properties that makes a clear distinction between the ways a classical and a quantum system can behave.
    [Show full text]
  • Caputo Fractional Derivative and Quantum-Like Coherence
    entropy Article Caputo Fractional Derivative and Quantum-Like Coherence Garland Culbreth 1,* , Mauro Bologna 2, Bruce J. West 3 and Paolo Grigolini 1 1 Center for Nonlinear Science, University of North Texas, P.O. Box 311427, Denton, TX 76201, USA; [email protected] 2 Departamento de Ingeniería Eléctrica-Electrónica, Universidad de Tarapacá, 1000000 Arica, Chile; [email protected] 3 Army Research Office, DEVCOM US Army Research Laboratory, Research Triangle Park, NC 27708, USA; [email protected] * Correspondence: [email protected] Abstract: We study two forms of anomalous diffusion, one equivalent to replacing the ordinary time derivative of the standard diffusion equation with the Caputo fractional derivative, and the other equivalent to replacing the time independent diffusion coefficient of the standard diffusion equation with a monotonic time dependence. We discuss the joint use of these prescriptions, with a phenomenological method and a theoretical projection method, leading to two apparently different diffusion equations. We prove that the two diffusion equations are equivalent and design a time series that corresponds to the anomalous diffusion equation proposed. We discuss these results in the framework of the growing interest in fractional derivatives and the emergence of cognition in nature. We conclude that the Caputo fractional derivative is a signature of the connection between cognition and self-organization, a form of cognition emergence different from the other source of anomalous diffusion, which is closely related to quantum coherence. We propose a criterion to detect the action of self-organization even in the presence of significant quantum coherence. We argue that statistical analysis of data using diffusion entropy should help the analysis of physiological processes hosting both forms of deviation from ordinary scaling.
    [Show full text]
  • Nthorder Multifrequency Coherence Functions: a Functional Path Integral Approach Conrad M
    Nthorder multifrequency coherence functions: A functional path integral approach Conrad M. Rose and Ioannis M. Besieris Citation: Journal of Mathematical Physics 20, 1530 (1979); doi: 10.1063/1.524213 View online: http://dx.doi.org/10.1063/1.524213 View Table of Contents: http://scitation.aip.org/content/aip/journal/jmp/20/7?ver=pdfcov Published by the AIP Publishing This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to IP: 128.173.125.76 On: Mon, 24 Mar 2014 17:26:14 Nth-order multifrequency coherence functions: A functional path integral approach~ Conrad M. Rose Naval Surface Weapons Center, Dahlgren, Virginia 22448 loannis M. Besieris Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061 (Received 21 August 1978) A functional (or path) integral applicable to a broad class of randomly perturbed media is constructed for the nth-order multi frequency coherence function (a quantity intimately linked to nth-order pulse statistics). This path integral is subsequently carried out explicitly in the case of a nondispersive, deterministically homogeneous medium, with a simplified (quadratic) Kolmogorov spectrum, and a series of new results are derived. Special cases dealing with the two-frequency mutual coherence function for plane and beam pulsed waves are considered, and comparisons are made with previously reported findings. 1. INTRODUCTION gation in the atmosphere and in lightguides, and underwater sound wave propagation) where the restriction to spatially There has been recently a mounting interest in the sub­ ject of propagation of pulsed signals through randomly per­ planar sources must be lifted.
    [Show full text]
  • IBM Reports Significant Progress in Superconducting Qubit Coherence Time and Demonstrates Complete Universal Quantum Gate Set Approaching Fault- Tolerant Thresholds
    IBM Reports Significant Progress in Superconducting Qubit Coherence Time and Demonstrates Complete Universal Quantum Gate Set Approaching Fault- tolerant Thresholds March 26, 2012 (HP45). Near the end of February 2012, researchers at IBM T.J. Watson Research Center (Yorktown Heights, NY, USA) reported significant progress towards quantum computing using superconducting qubits. The following two short papers/letters were posted in arXiv and submitted for publication: “Superconducting qubit in waveguide cavity with coherence time approaching 0.1 ms” by Chad Rigetti et al. (arXiv:1202.5533v1 [quant-ph], February 24, 2012) and “Complete universal quantum gate set approaching fault-tolerant thresholds” by Jerry M. Chow et al. (arXiv:1202.5344v1 [quant-ph], February 23, 2012). The first letter describes a qubit with an observed quantum coherence time of T2* = 95 s and energy relaxation time T1 = 70 s. The system consists of a single Josephson junction transmon qubit embedded in an empty three-dimensional (3D) copper waveguide cavity whose lowest eigenmode is dispersively coupled to the qubit transition. The authors attribute the factor of four increase in the coherence 6 6 quality factors Q2, Q1 (Q2 ≈ 2.5x10 and Q1 ≈ 1.8x10 ) relative to previous reports to device modifications aimed at reducing qubit dephasing from residual cavity photons. These modifications represent the gist of the letter. The attained level of T2* and T1 places the device well within the range of performance required for large-scale tests of error correction fault-tolerant quantum computing. The reported work confirms the basic reproducibility of the breakthrough work by Paik et al. [1] (see HP44), who first reported enhanced coherence times when embedding a transmon qubit in a superconducting 3D waveguide catity.
    [Show full text]
  • Coherent X-Rays: Overview by Malcolm Howells
    Coherent x-rays: overview by Malcolm Howells Lecture 1 of the series COHERENT X-RAYS AND THEIR APPLICATIONS A series of tutorial–level lectures edited by Malcolm Howells* *ESRF Experiments Division ESRF Lecture Series on Coherent X-rays and their Applications, Lecture 1, Malcolm Howells CONTENTS Introduction to the series Books History The idea of coherence - temporal, spatial Young's slit experiment Coherent experiment design Coherent optics The diffraction integral Linear systems - convolution Wave propagation and passage through a transparency Optical propagators - examples Future lectures: 1. Today 2. Quantitative coherence and application to x-ray beam lines (MRH) 3. Optical components for coherent x-ray beams (A. Snigirev) 4. Coherence and x-ray microscopes (MRH) 5. Phase contrast and imaging in 2D and 3D (P. Cloetens) 6. Scanning transmission x-ray microscopy: principles and applications (J. Susini) 7. Coherent x-ray diffraction imaging: history, principles, techniques and limitations (MRH) 8. X-ray photon correlation spectroscopy (A. Madsen) 9. Coherent x-ray diffraction imaging and other coherence techniques: current achievements, future projections (MRH) ESRF Lecture Series on Coherent X-rays and their Applications, Lecture 1, Malcolm Howells COHERENT X-RAYS AND THEIR APPLICATIONS A series of tutorial–level lectures edited by Malcolm Howells* Mondays 5.00 pm in the Auditorium except where otherwise stated 1. Coherent x-rays: overview (Malcolm Howells) (April 7) (5.30 pm) 2. Coherence theory: application to x-ray beam lines (Malcolm Howells) (April 21) 3. Optical components for coherent x-ray beams (Anatoli Snigirev) (April 28) 4. Coherence and x-ray microscopes (Malcolm Howells) (May 26) (CTRL room ) 5.
    [Show full text]