Ebook: Recent Advances in Metrology and Fundamental Constants

This Course on Recent Advances in Metrology and Fundamental Constants was held in Varenna in July and August 2000 and was organized by the Italian Physical Society, the Istituto Elettrotecnico Nazionale of Italy, and the Bureau International des Poids et Mesures also as a contribution to the celebration of the 125 years of the Metre Convention. Such an endeavour finds its justification, besides the particular event, in the need to provide a co-ordinated set of lectures that from time to time present the relevant progress in Metrology.

This is the third of the Enrico Fermi Schools on Metrology and Fundamental Constants, the first was held in 1976 and the second in 1989. They have all been supported by the direct presence of BIPM via the Director pro tempore and by the strong presence of the National Metrological Institutions, articulated in two directions: from one side the many expert lecturers from the Institutes and from the other the attendance of some young researchers from the Institutes.

The exchange between physics and metrology is always fascinating and exciting. Many are the open problems in physics that call for extremely precise standards, many are the advances in metrology made possible by a deep and assiduous study of the underlying physics. One has just to think of the enormous sophistication required in the measurements of some absolute quantities such as the Avogadro, the gas, or the gravitational constants. It is also worth noticing that not only the units of a metrological system are interrelated through the fundamental constants, but also the latter find their full significance when they are determined through the most exacting metrological experiments.

Over the past decade many improvements took place and these were discussed at the School; from one side the old caesium SI second definition has found a new realisation, with the “fountain” approach, replacing the classical thermal atomic beam. The use of “cold” atom techniques, in which bunches of inert atoms are collected, slowed down, and cooled, has opened a number of new and unexpected avenues for metrology and fundamental constants, one of these possibilities being atom interferometry.

Another important “quantum jump” was the demonstration of the possibility of performing a direct frequency division in the visible, using ultra-short femtosecond pulses. In addition, the possibility of “counting” electrons or photons gave a fundamental support to the development of single-electron capacitance standards and to new scenarios in the absolute calibration of photo-detectors.

The success of this third Course was made possible by the close co-operation and strict dedication of many Institutions and persons.

The directors wish to thank the NMIs for their support in ideas, lectures, and students.

Moreover, the Italian Physical Society, the Bureau International des Poids et Mesures, the “Istituto Elettrotecnico Nazionale”, the “Istituto di Metrologia G. Colonnetti” of CNR, the European Community, the Italian Ministry of Foreign Affairs, the International Union of Radio Science, and the UNESCO, are all acknowledged for having provided financial support for the attendance of several students.

The directors also wish to express their warm thanks to all the lecturers, who shared their time and expertise with the students, not only during the scheduled lectures, but also because their enthusiasm and competence was one of the fundamental elements for the success of the Course.

A particular debt of gratitude must be expressed to P. Tavella for her dedicated work as Scientific Secretary.

The directors wish to extend their gratitude to the some seventy well-qualified students who attended this Course from 18 different countries and who contributed with simulating and interacting discussions.

Finally, the extremely valuable help of Mrs. B. Alzani and C. Vasini, of the Italian Physical Society, is warmly acknowledged.

S. Leschiutta and T. J. Quinn

1. Introduction

2. History of the development of the SI

3. The two classes of SI units

4. The SI prefixes

5. SI units in the framework of general relativity

6. Units outside the SI

7. Conclusions

1. Introduction

2. The metre convention

3. The 21st CGPM

4. The broader organization of metrology

5. International collaboration in metrology through regional cooperations

6. The CIPM MRA

7. Conclusions

1. Reference material

2. Preamble

3. Quantities

4. Units

5. The equations of physics, and definitional constants

6. Coherent systems of units

7. Dimensions

8. Base quantities and units; the equations of physics; derived quantities and units; and the International System

9. The SI prefixes

10. On the number of independent base quantities and units

11. Electromagnetic quantities and units

12. Summary

1. Introduction and a disclaimer

2. Focal roles of measurement

3. Relation measurement-physics: classical approach

4. “Modern” approach

5. “Post-modern” approach

6. The “theory of measurement”

7. Some good reasons, old and new, to further fostering metrology

8. Further readings

1. Introduction

2. Measurement in manufacturing industries

3. Measurement in navigation and communications

4. Measurements in medical diagnosis and therapy

5. Global climate studies

6. Accuracy rather than simply reproducibility

7. National and international measurement standards

8. How much does it cost to maintain the world's measurement system?

9. Conclusions

1. Introduction

2. The various facets of metrology

3. Metrology appears as a discipline (why, where, when)

4. Four levels of education

1. Introduction

2. The fundamental constants as “natural” units

3. The fundamental constants and unit systems

4. The different types of interaction in physics

5. The constancy of the constants

6. How well do we know their values?

7. Conclusion

1. Introduction

2. The increased involvement of the fundamental constant with the SI units

3. The fundamental constants and electrical measurements

4. The role of the fundamental constants in the gap between the national standards laboratoires and the market place

5. Are there ultimate limits to the accuracy of science and technology?

1. Introduction

2. The measurement of G

3. Conclusions

1. Introduction

2. Origins of the Planck constant: the radiation law

3. Early measurements of the Planck constant, h

4. Modern determinations of h: the Josephson effect and quantum Hall effect era

5. Determinations via the realization of the watt

6. Other measurements providing information about h

7. Impact on the values of the constants

1. Introduction

2. Historical background

3. The XRCD method

4. Conclusion

1. Introduction

2. Basic applications of speed-of-sound measurements

3. Theoretical basis of measurement

4. Experimental techniques

5. Acoustic determination of the universal gas constant R

1. Precise routes to α

2. Towards α determination from fine structure of helium atom

3. Improving the accuracy of helium spectroscopy

4. Conclusions and final remarks

1. Introduction

2. The physical basis for mass metrology

3. Density and volume

4. The kilogram

5. Traceability to the international prototype

6. Official copies, national prototypes and prototypes of the BIPM

7. Should we change the definition of the SI kilogram?

8. Using mass comparators to compare masses

9. Influencing factors

10. Conclusion

1. Introduction

2. Principles of the IQHE

3. Measurement techniques

4. Experimental tests of the QHE

5. The QHE and fundamental constants

6. AC measurements of the QHR

1. Introduction

2. Basic physics of SET devices

3. Metrological applications of SET devices

4. Impact on fundamental constants and the SI

5. Conclusion

1. Introduction

2. Macroscopic quantum coherence in superconductors: Josephson voltage standards and thei precision

3. Josephson array voltage standard for 10 V

4. Programmable Josephson voltage standards

5. Conclusions

1. Introduction

2. Radiative forces

3. Deceleration and cooling of an atomic beam

4. Traps for neutral atoms

5. Sub-Doppler laser cooling

6. Metrology with cold atoms

7. Coherent manipulation of Bose-Einstein condensates with light

8. Nonlinear atom optics with Bose-Einstein condensates

1. Introduction

2. The atomic clock

3. Impact of atomic frequency standards on the SI

4. Incidence on the study of fundamental physical phenomena and determination of universal physical constants

1. The way to the international unit of length (historical review)

2. Changes in the definitions of the meter

3. Realization methods of the meter

4. Basic schemes of optical wavelength/frequency standards

5. Examples of optical frequency standards

6. Optical frequency synthesis

7. Outlook and conclusion

1. Introduction

2. Measurement tasks

3. Dimensional metrology---general approach and advances

4. New or improved measurement methods and devices

5. Conclusions