Contributions of precision engineering to the revision of the SI

All measurements performed in science and industry are based on the International System of Units, the SI. It has been proposed to revise the SI following an approach which was implemented for the redefinition of the unit of length, the metre, namely to define the SI units by fixing the numerical values of so-called defining constants, including c, h, e, k and NA. We will discuss the reasoning behind the revision, which will likely be put into force in 2018. Precision engineering was crucial to achieve the required small measurement uncertainties and agreement of measurement results for the defining constants

Transporting and manipulating single electrons in surface-acoustic-wave minima

A surface acoustic wave (SAW) can produce a moving potential wave that can trap and drag electrons along with it. We review work on using a SAW to create moving quantum dots containing single electrons, with the aims of developing a current standard, emitting single photons, transferring single electrons between static quantum dots, and investigating non-adiabatic effects

Amplitude, temperature, and frequency dependence of quantum pumps in semiconductor heterostructures

In the rapidly growing field of integrated quantum devices, two particular areas of interest are the development of an on-chip cryogenic current comparator (CCC) for completing the metrological triangle and the development of integrated de- vices for fast qubit operations. This thesis aims to significantly further our understanding of a quantum pump, a device integral to the CCC and potentially critical for realising fast qubit operations. A quantum pump is a device that transfers a discrete number of electrons between two electrically isolated regions when a potential barrier is cyclically oscillated. Initially, quantum pumps were single electron turnstile devices, which were limited in operational frequency by the Coulomb potential of the turnstile. Modern quantum pumps, utilising a dynamic quantum dot in a 2-dimensional electron gas (2DEG), are not limited by frequency. The fast operation of these modern pumps makes them very promising devices for accurately measuring the electron charge and performing fast qubit operations. In this study, we address the technical challenges of measuring a Al- GaAs/GaAs quantum pump and detail the processing and measurement setup. One of the challenges is rectified current swamping pump current. We develop a model for the rectified current and investigate ways to suppress it. We then show how the accuracy of a quantum pump changes as a function of amplitude, temperature, and frequency, and develop a model towards explaining the changes

Single-electron current sources: towards a refined definition of ampere

Controlling electrons at the level of elementary charge $e$ has been demonstrated experimentally already in the 1980's. Ever since, producing an electrical current $ef$, or its integer multiple, at a drive frequency $f$ has been in a focus of research for metrological purposes. In this review we first discuss the generic physical phenomena and technical constraints that influence charge transport. We then present the broad variety of proposed realizations. Some of them have already proven experimentally to nearly fulfill the demanding needs, in terms of transfer errors and transfer rate, of quantum metrology of electrical quantities, whereas some others are currently "just" wild ideas, still often potentially competitive if technical constraints can be lifted. We also discuss the important issues of read-out of single-electron events and potential error correction schemes based on them. Finally, we give an account of the status of single-electron current sources in the bigger framework of electric quantum standards and of the future international SI system of units, and briefly discuss the applications and uses of single-electron devices outside the metrological context.Comment: 55 pages, 38 figures; (v2) fixed typos and misformatted references, reworded the section on AC pump

Proceedings of the Eleventh Annual Precise Time and Time Interval (PTTI) Application and Planning Meeting

Thirty eight papers are presented addressing various aspects of precise time and time interval applications. Areas discussed include: past accomplishments; state of the art systems; new and useful applications, procedures, and techniques; and fruitful directions for research efforts

A self-referenced single-electron current source

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Chemical vapor deposited graphene for quantum Hall resistance standards

In this PhD project, we address the different aspects in the development of CVD graphene based quantum Hall resistance standards (QHR) for metrological applications. An interesting application of graphene is its use in developing quantum Hall resistance standards (QHR). Resistors are one of the most widely used passive components in electrical circuits, a precise and reliable resistance standard is thus vital for the appropriate calibration and reproducibility of various electronic systems during manufacturing. Standard wire-wound resistors suffer from degradation and at best offer an uncertainty of few parts per million (ppm). The quantized Hall resistance plateaus were recognized to serve as the ultimate reference for resistance standards. The quantized Hall resistances is defined in terms of Planck constant h and electron charge e and are independent of sample dimensions. These advantages along with the universality and robustness of the quantum Hall effect offers an unparalleled advantage over passive resistor standards. Graphene offers a unique advantage in realization of a convenient resistance standard, operating at easier measurement conditions. Low dissipation QHE in CVD graphene has been elusive due to several reasons. The various aspects considered within this project involve the synthesis of large area CVD graphene films on copper foil and its thorough characterization using electrical transport, Raman spectroscopy, X-ray photoelectron spectroscopy and low-energy-electron microscopy. As a highlight, we were able to demonstrate high precision resistance quantization in CVD graphene with an accuracy within 30 parts per billion

The 25th Annual Precise Time and Time Interval (PTTI) Applications and Planning Meeting

Papers in the following categories are presented: recent developments in rubidium, cesium, and hydrogen-based frequency standards, and in cryogenic and trapped-ion technology; international and transnational applications of precise time and time interval (PTTI) technology with emphasis on satellite laser tracking networks, GLONASS timing, intercomparison of national time scales and international telecommunication; applications of PTTI technology to the telecommunications, power distribution, platform positioning, and geophysical survey industries; application of PTTI technology to evolving military communications and navigation systems; and dissemination of precise time and frequency by means of GPS, GLONASS, MILSTAR, LORAN, and synchronous communications satellites

NBS monograph

From Abstract: "This is a tutorial Monograph describing various aspects of time and frequency (T/F). Included are chapters relating to elemental concepts of precise time and frequency; basic principles of quartz oscillators and atomic frequency standards; historical review, recent progress, and current status of atomic frequency standards; promising areas for developing future primary frequency standards; relevance of frequency standards to other areas of metrology including a unified standard concept; statistics of T/F data analysis coupled with the theory and construction of the NBS atomic time scale; an overview of T/F dissemination techniques; and the standards of T/F in the USA. The Monograph addresses both the specialist in the field as well as those desiring basic information about time and frequency.