Time and Frequency Division Report
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What Time Is It?
The Astronomical League A Federation of Astronomical Societies Astro Note E3 – What Time Is It? Introduction – There are many methods used to keep time, each having its own special use and advantage. Until recently, when atomic clocks became available, time was reckoned by the Earth's motions: one rotation on its axis was a "day" and one revolution about the Sun was a "year." An hour was one twenty-fourth of a day, and so on. It was convenient to use the position of the Sun in the sky to measure the various intervals. Apparent Time This is the time kept by a sundial. It is a direct measure of the Sun's position in the sky relative to the position of the observer. Since it is dependent on the observer's location, it is also a local time. Being measured according to the true solar position, it is subject to all the irregularities of the Earth's motion. The reference time is 12:00 noon when the true Sun is on the observer's meridian. Mean Time Many of the irregularities in the Earth's motion are due to its elliptical orbit. In order to add some consistency to the measure of time, we use the concept of mean time. Mean time uses the position of a fictitious "mean Sun" which moves smoothly and uniformly across the sky and is insensitive to the irregularities of the Earth’s motion. A mean solar day is 24 hours long. The "Equation of Time," tabulated in almanacs and represented on maps by the analemma, provides the correction between mean and apparent time to allow for the eccentricity of the Earth's orbit. -
Information and Entropy in Quantum Theory
Information and Entropy in Quantum Theory O J E Maroney Ph.D. Thesis Birkbeck College University of London Malet Street London WC1E 7HX arXiv:quant-ph/0411172v1 23 Nov 2004 Abstract Recent developments in quantum computing have revived interest in the notion of information as a foundational principle in physics. It has been suggested that information provides a means of interpreting quantum theory and a means of understanding the role of entropy in thermodynam- ics. The thesis presents a critical examination of these ideas, and contrasts the use of Shannon information with the concept of ’active information’ introduced by Bohm and Hiley. We look at certain thought experiments based upon the ’delayed choice’ and ’quantum eraser’ interference experiments, which present a complementarity between information gathered from a quantum measurement and interference effects. It has been argued that these experiments show the Bohm interpretation of quantum theory is untenable. We demonstrate that these experiments depend critically upon the assumption that a quantum optics device can operate as a measuring device, and show that, in the context of these experiments, it cannot be consistently understood in this way. By contrast, we then show how the notion of ’active information’ in the Bohm interpretation provides a coherent explanation of the phenomena shown in these experiments. We then examine the relationship between information and entropy. The thought experiment connecting these two quantities is the Szilard Engine version of Maxwell’s Demon, and it has been suggested that quantum measurement plays a key role in this. We provide the first complete description of the operation of the Szilard Engine as a quantum system. -
Illustrating Time's Shadow Supplements
Illustrating Time's Shadow Supplements Supplemental Shadows This book addresses small indoor sundials of wood, glass, and PVC, as well as outside garden dials of glass, clay, tile, and common building materials. Less common dial features such as the inclined decliner and calendar or declination curves, are covered, as well as the astrolabe, other altitude dials and azimuth time keepers. This book uses empirical, geometric, trigonometric, CAD (computer aided design) both 2d and 3d, spreadsheet, procedural programming, tabular methods, and other techniques. Tables are provided. Simon Wheaton-Smith 1 ILLUSTRATING TIME’S SHADOW The Supplements Supplemental Shadows enhances both the book Illustrating Time’s Shadow as well as its associated Appendices by Simon Wheaton-Smith ISBN 978-0-9960026-1-5 Library of Congress Control Number: 2014904840 Simon Wheaton-Smith www.illustratingshadows.com (c) 2004-2018 Simon Wheaton-Smith All rights reserved. June 12, 2018 2 THE ILLUSTRATING SHADOWS COLLECTION Illustrating Shadows provides several books or booklets:- Simple Shadows Build a horizontal dial for your location. Appropriate theory. Cubic Shadows Introducing a cube dial for your location. Appropriate theory. Cutting Shadows Paper cutouts for you to make sundials with. Illustrating Times Shadow the big book Illustrating Times Shadow ~ Some 400 pages covering almost every aspect of dialing. Includes a short appendix. Appendices Illustrating Times Shadow ~ The Appendices ~ Some 180 pages of optional detailed appendix material. Supplement Supplemental Shadows ~ Material in the form of a series of articles, covers more on the kinds of time, declination confusion, other proofs for the vertical decliner, Saxon, scratch, and mass dials, Islamic prayer times (asr), dial furniture, and so on! Programming Shadows A book discussing many programming languages, their systems and how to get them, many being free, and techniques for graphical depictions. -
NIST Time and Frequency Services (NIST Special Publication 432)
Time & Freq Sp Publication A 2/13/02 5:24 PM Page 1 NIST Special Publication 432, 2002 Edition NIST Time and Frequency Services Michael A. Lombardi Time & Freq Sp Publication A 2/13/02 5:24 PM Page 2 Time & Freq Sp Publication A 4/22/03 1:32 PM Page 3 NIST Special Publication 432 (Minor text revisions made in April 2003) NIST Time and Frequency Services Michael A. Lombardi Time and Frequency Division Physics Laboratory (Supersedes NIST Special Publication 432, dated June 1991) January 2002 U.S. DEPARTMENT OF COMMERCE Donald L. Evans, Secretary TECHNOLOGY ADMINISTRATION Phillip J. Bond, Under Secretary for Technology NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY Arden L. Bement, Jr., Director Time & Freq Sp Publication A 2/13/02 5:24 PM Page 4 Certain commercial entities, equipment, or materials may be identified in this document in order to describe an experimental procedure or concept adequately. Such identification is not intended to imply recommendation or endorsement by the National Institute of Standards and Technology, nor is it intended to imply that the entities, materials, or equipment are necessarily the best available for the purpose. NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY SPECIAL PUBLICATION 432 (SUPERSEDES NIST SPECIAL PUBLICATION 432, DATED JUNE 1991) NATL. INST.STAND.TECHNOL. SPEC. PUBL. 432, 76 PAGES (JANUARY 2002) CODEN: NSPUE2 U.S. GOVERNMENT PRINTING OFFICE WASHINGTON: 2002 For sale by the Superintendent of Documents, U.S. Government Printing Office Website: bookstore.gpo.gov Phone: (202) 512-1800 Fax: (202) -
Notes on the Theory of Quantum Clock
NOTES ON THE THEORY OF QUANTUM CLOCK I.Tralle1, J.-P. Pellonp¨a¨a2 1Institute of Physics, University of Rzesz´ow,Rzesz´ow,Poland e-mail:[email protected] 2Department of Physics, University of Turku, Turku, Finland e-mail:juhpello@utu.fi (Received 11 March 2005; accepted 21 April 2005) Abstract In this paper we argue that the notion of time, whatever complicated and difficult to define as the philosophical cat- egory, from physicist’s point of view is nothing else but the sum of ’lapses of time’ measured by a proper clock. As far as Quantum Mechanics is concerned, we distinguish a special class of clocks, the ’atomic clocks’. It is because at atomic and subatomic level there is no other possibility to construct a ’unit of time’ or ’instant of time’ as to use the quantum transitions between chosen quantum states of a quantum ob- ject such as atoms, atomic nuclei and so on, to imitate the periodic circular motion of a clock hand over the dial. The clock synchronization problem is also discussed in the paper. We study the problem of defining a time difference observable for two-mode oscillator system. We assume that the time dif- ference obsevable is the difference of two single-mode covariant Concepts of Physics, Vol. II (2005) 113 time observables which are represented as a time shift covari- ant normalized positive operator measures. The difficulty of finding the correct value space and normalization for time dif- ference is discussed. 114 Concepts of Physics, Vol. II (2005) Notes on the Theory of Quantum Clock And the heaven departed as a scroll when it is rolled together;.. -
Engineering Ultrafast Quantum Frequency Conversion
Engineering ultrafast quantum frequency conversion Der Naturwissenschaftlichen Fakultät der Universität Paderborn zur Erlangung des Doktorgrades Dr. rer. nat. vorgelegt von BENJAMIN BRECHT aus Nürnberg To Olga for Love and Support Contents 1 Summary1 2 Zusammenfassung3 3 A brief history of ultrafast quantum optics5 3.1 1900 – 1950 ................................... 5 3.2 1950 – 2000 ................................... 6 3.3 2000 – today .................................. 8 4 Fundamental theory 11 4.1 Waveguides .................................. 11 4.1.1 Waveguide modelling ........................ 12 4.1.2 Spatial mode considerations .................... 14 4.2 Light-matter interaction ........................... 16 4.2.1 Nonlinear polarisation ........................ 16 4.2.2 Three-wave mixing .......................... 17 4.2.3 More on phasematching ...................... 18 4.3 Ultrafast pulses ................................. 21 4.3.1 Time-bandwidth product ...................... 22 4.3.2 Chronocyclic Wigner function ................... 22 4.3.3 Pulse shaping ............................. 25 5 From classical to quantum optics 27 5.1 Speaking quantum .............................. 27 iii 5.1.1 Field quantisation in waveguides ................. 28 5.1.2 Quantum three-wave mixing .................... 30 5.1.3 Time-frequency representation .................. 32 5.1.3.1 Joint spectral amplitude functions ........... 32 5.1.3.2 Schmidt decomposition ................. 35 5.2 Understanding quantum ........................... 36 5.2.1 Parametric -
Overview of the National Measurement System's Time and Frequency Programme
Overview of the National Measurement System’s Time and Frequency Programme Dale Henderson Projects to support the maintenance of UTC “The Maintenance and Development of UTC(NPL)” The objectives of this project are to support the operation and development of the international civil time scale, Coordinated Universal Time (UTC), in partnership with the BIPM and the national time standards laboratories from other countries around the world; and to provide a reference time standard for the UK that is traceable to the international civil time scale, Coordinated Universal Time (UTC). Its main deliverable is UTC(NPL), a continuously operating national time scale that is traceable to UTC, with the uncertainty in the UTC-UTC(NPL) offsets published in the BIPM Circular T to be established with an uncertainty of ± 5 ns (1s) or better. UTC and TAI UT-1 is based on siderial time as monitored by the IERS TAI maintained by BIPM under the Metre Convention TAI is an Atomic time, step interval 1 SI second on the Geoid UTC is “owned” by ITU (recommendation TF 460) and has the rate of TAI but is stepped to follow UT-1 International time-keeping since 1972 40 time laboratories around the world with more than 200 atomic clocks keep world time Laboratory time standards compared using satellite links Global standards – International Atomic Time (TAI) and Coordinated Universal Time (UTC) – are computed by the BIPM each calendar month System calibrated by ~8 primary frequency standards 150 100 50 USNO PTB 0 NPL 50800 51300 51800 IEN -50 UTC - UTC(k) [ns] -100 -150 -
Notes on the Theory of Quantum Clock
NOTES ON THE THEORY OF QUANTUM CLOCK I.Tralle1, J.-P. Pellonp¨a¨a2 1Institute of Physics, University of Rzesz´ow,Rzesz´ow,Poland e-mail:[email protected] 2Department of Physics, University of Turku, Turku, Finland e-mail:juhpello@utu.fi (Received 11 March 2005; accepted 21 April 2005) Abstract In this paper we argue that the notion of time, whatever complicated and difficult to define as the philosophical cat- egory, from physicist’s point of view is nothing else but the sum of ’lapses of time’ measured by a proper clock. As far as Quantum Mechanics is concerned, we distinguish a special class of clocks, the ’atomic clocks’. It is because at atomic and subatomic level there is no other possibility to construct a ’unit of time’ or ’instant of time’ as to use the quantum transitions between chosen quantum states of a quantum ob- ject such as atoms, atomic nuclei and so on, to imitate the periodic circular motion of a clock hand over the dial. The clock synchronization problem is also discussed in the paper. We study the problem of defining a time difference observable for two-mode oscillator system. We assume that the time dif- ference obsevable is the difference of two single-mode covariant Concepts of Physics, Vol. II (2005) 113 time observables which are represented as a time shift covari- ant normalized positive operator measures. The difficulty of finding the correct value space and normalization for time dif- ference is discussed. 114 Concepts of Physics, Vol. II (2005) Notes on the Theory of Quantum Clock And the heaven departed as a scroll when it is rolled together;.. -
The Boundaries of Nature: Special & General Relativity and Quantum
“The Boundaries of Nature: Special & General Relativity and Quantum Mechanics, A Second Course in Physics” Edwin F. Taylor's acceptance speech for the 1998 Oersted medal presented by the American Association of Physics Teachers, 6 January 1998 Edwin F. Taylor Center for Innovation in Learning, Carnegie Mellon University, Pittsburgh, PA 15213 (Now at 22 Hopkins Road, Arlington, MA 02476-8109, email [email protected] , web http://www.artsaxis.com/eftaylor/ ) ABSTRACT Public hunger for relativity and quantum mechanics is insatiable, and we should use it selectively but shamelessly to attract students, most of whom will not become physics majors, but all of whom can experience "deep physics." Science, engineering, and mathematics students, indeed anyone comfortable with calculus, can now delve deeply into special and general relativity and quantum mechanics. Big chunks of general relativity require only calculus if one starts with the metric describing spacetime around Earth or black hole. Expressions for energy and angular momentum follow, along with orbit predictions for particles and light. Feynman's Sum Over Paths quantum theory simply commands the electron: Explore all paths. Students can model this command with the computer, pointing and clicking to tell the electron which paths to explore; wave functions and bound states arise naturally. A second full year course in physics covering special relativity, general relativity, and quantum mechanics would have wide appeal -- and might also lead to significant advancements in upper-level courses for the physics major. © 1998 American Association of Physics Teachers INTRODUCTION It is easy to feel intimidated by those who have in the past received the Oersted Medal, especially those with whom I have worked closely in the enterprise of physics teaching: Edward M. -
Kintaro Hattori in 1881 Founded the Company That Was to Become Seiko
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Representation of Date and Time Data Standard
REPRESENTATION OF DATE AND TIME DATA STANDARD Standard No.: EX000013.1 January 6, 2006 This standard has been produced through the Environmental Data Standards Council (EDSC). Representation of Date and Time Data Standard Std No.: EX000013.1 Foreword The Environmental Data Standards Council (EDSC) identifies, prioritizes and pursues the creation of data standards for those areas where information exchange standards will provide the most value in achieving environmental results. The Council involves Tribes and Tribal Nations, state and federal agencies in the development of the standards and then provides the draft materials for general review. Business groups, non-governmental organizations, and other interested parties may then provide input and comment for Council consideration and standard finalization. Standards are available at http://www.epa.gov/datastandards 1.0 INTRODUCTION This is a format standard which indicates how one displays a particular day within a Gregorian calendar month and specifies an instance of time in the day. Time is expressed in Coordinated Universal Time (UTC). UTC is the official time scale, maintained by the Bureau International des Poids et Mesures (BIPM), and the International Earth Rotation Service (IERS). Examples of the formats follow: a. Date only format When the need is for an expression only of a calendar date, then the complete representation shall be a single numeric data element comprising eight digits, where [YYYY] represents a calendar year, [MM] the ordinal number of a calendar month within the calendar year, and [DD] the ordinal number of a day within the calendar month. Extended format: YYYY-MM-DD EXAMPLE 1985-04-12 b. -
Best Practices for Leap Second Event Occurring on 30 June 2015
26 May 2015 Best Practices for Leap Second Event Occurring on 30 June 2015 Sponsored by the National Cybersecurity and Communications Integration Center in coordination with the United States Naval Observatory, National Institute of Standards and Technology, the USCG Navigation Center, and the National Coordination Office for Space-Based Positioning, Navigation and Timing. This product is intended to assist federal, state, local, and private sector organizations with preparations for the 30-June 2015 Leap Second event. Entities using precision time should be mindful that no leap second adjustment has occurred on a non- holiday weekday in the past decade. Of the three leap seconds implemented since 2000, two have been scheduled on 31 December and the most recent was on Sunday, 1 July 2012. Please report operational challenges you experience to the following organizations: GPS -- United States Coast Guard Navigation Center (NAVCEN), via the NAVCEN Website, http://www.navcen.uscg.gov/ under "Report a GPS Problem" Network Timing Protocols (NTP) -- Michael Lombardi at NIST, Boulder, Colorado at 303-497- 3212, or [email protected]. ============================================= 1. Leap Second Introduction The Coordinated Universal Time (UTC) time standard, based on atomic clocks, is widely used for international timekeeping and as the reference for time in most countries. UTC is the basis of legal time for most of the world. UTC must be adjusted at irregular intervals to maintain its correlation to mean solar time due to irregularities in the Earth’s rotation. These adjustments, called leap seconds, are pre-determined. The next leap second will occur on 30 June 2015 at 23:59:59 UTC.