Ernst O. Göbel and Uwe Siegner, Physikalisch-Technische Bundesanstalt, PTB (the National Metrology Institute of Germany) have worked in the field of metrology for many years and both are experienced university lecturers.

Ernst O. Göbel, PhD, was president of PTB from 1995 till 2011. His scientific background is in solid state and laser physics and laser spectroscopy. He was a member of the Comité International des Poids et Mesures, CIPM, from 1997 till 2013, and from 2004 till 2010, its president. He had been full professor at the University of Marburg and is member of several national and international academies. He has issued more than three hundred original scientific publications and is recipient of several scientific awards such as the Leibniz Prize of the German Research Foundation (DFG) and the Max Born Award jointly provided by the Institute of Physics (London) and the German Physical Society (DFG).

Uwe Siegner, PhD, is the head of the Electricity Division of PTB and a member of the Comité Consultatif d`Électricité et Magnétisme, CCEM, of the CIPM. He is an honorary professor at the Technical University of Braunschweig and a principal investigator of the Braunschweig International Graduate School of Metrology. His scientific background is in solid state physics and ultrafast laser optics and he has authored or co-authored about 100 original scientific publications in these fields.

Foreword
Preface
List of Abbreviations
INTRODUCTION
BASICS
Measurement
The SI (Système International d'Unités)
LASER COOLING, ATOMIC CLOCKS, AND THE SECOND
Techniques for Laser Cooling
The Cs-Fountain Clock
Optical Clocks
SUPERCONDUCTIVITY, JOSEPHSON EFFECT, AND FLUX QUANTA
Josephson Effect and Quantum Voltage Standards
Flux Quanta and Superconducting Quantum Interference Devices
QUANTUM HALL EFFECT
Basic Physics of Three- and Two Dimensional Semiconductors
Two-Dimensional Electron Systems in Real Semiconductors
The Hall Effect
Quantum Hall Resistance Standards
SINGLE-CHARGE TRANSFER DEVICES AND THE NEW AMPERE
Basic Physics of Single-Electron Transport
Quantized Current Sources
Consistency Tests: Quantum Metrology Triangle
PLANCK CONSTANT, THE NEW KILOGRAM, AND THE MOLE
The Avogadro Experiment
The Watt Balance Experiment
The Mole, Unit of Amount of Susbstance
BOLTZMANN CONSTANT AND THE NEW KELVIN
Primary Thermometers
Realization and Disseminiation of the New Kelvin
SINGLE-PHOTON METROLOGY AND QUANTUM RADIOMETRY
Single-Photon Sources
Single-Photon Detectors
Metrological Challenges