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Atomic Clocks
Physical Seminar- Quantum Optics and Nanophotonics -
Peter Deiml 20.05.2014
Quantum Optics and Nanophotonics Atomic Clocks Peter Deiml 2
Table of contents
• Why do we need an exact definition of time?
• Current time standard
• Spectroscopy
• Ramsey-Spectroscopy
• Caesium beam clock
• (Laser Cooling)
• Caesium fountain clock
• Outlook: Optical Clock
3Quantum Optics and Nanophotonics Atomic Clocks Peter Deiml
Why do we need an exact definition of time? [Bauch, 2003],[Bauch, 2012]
“The accurate measurement of time and frequency is vital to the success of many fields of science and technology.” [Bauch, 2003]
Some scientific examples:
• Other SI-units (e.g. meter)
based upon the second
• Spectrum of atoms (QM,QED)
• „Proof“ of equivalence principle,
SR, GR (Hafele-Keating-/ Maryland-
experiment)
• Gravitational waves
• Fine structure constant
constant?
Some everyday examples:
• Global Positioning System
(GPS)
• Telecommunication
• Supply of energy
Fig. 2: NAVSTAR satellite [Wiki GPS, 2014]Fig. 1: Hafele, Keating
& stewardess aboard airplane with two atomic clocks [Wiki HKE, 2014]
4
Definition of the second (1967)
„The second is the duration of 9192631770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom“ [BIPD, 2006]
Quantum Optics and Nanophotonics Atomic Clocks Peter Deiml
• Why exactly 9192631770 periods of the radiation?
• Why atomic properties?
• Why the Cs-133 atom?
• Why hyperfine levels?
Current time standard
→ value equals to ephimerises second Fig. 3: Solar system with sun and the nine planets (not true to scale) [SeaSky, 2014]
Quantum Optics and Nanophotonics Atomic Clocks Peter Deiml 5
Why atomic properties? [Bauch, 2012]
Current time standard
„ Zeit [ist] die Stellung des kleinen Zeigers meiner Uhr “ [Einstein, 1905]
Fig. 4: Spacetime in special relativity [Wiki SR, 2014]
• Every frame of reference has its own time
Time determined by natural constants!
• Atomic properties determined by natural constants (in rest frame of the atom)
Quantum Optics and Nanophotonics Atomic Clocks Peter Deiml 6
Current time standard
Why the Cs-133 atom? [PTB]
• Technology for measuring the resonance frequency was available in 1967
• Small thermal velocity due to large mass (later: Doppler effect → 0)
• Only two hyperfine levels in the ground state
• The only natural isotope of caesium
• Small boiling point (670°C)
• Transition has small natural line width
Quantum Optics and Nanophotonics Atomic Clocks Peter Deiml 7
Why hyperfine levels? [Audoin et al., 2005]
Current time standard
Quantum number configuration of the outermost
electron of Cs-133:
Fig. 6: Cutting of the hyperfine structure of Cs-133[Bauch, 2003]
• No fine structure (J)
• Transition for time standard: F = 3 ↔ F = 4
Quantum Optics and Nanophotonics Atomic Clocks Peter Deiml 8
Spectroscopy
General ideaInvestigation of the answer of atoms or molecules to a laserbeam
Examples:
• Information about structure of stars Fig. 8: Dispersion of white light by a prism [Wiki SpC, 2014]
Fig. 7: UVES on the very large telescope on Cerro Paranal (Chile)[Wiki SpC, 2014]
• Scientific applications: medicine (MRT),
chemistry, biology
Perfect method for measurement of the second
Quantum Optics and Nanophotonics Atomic Clocks Peter Deiml 99
Doppler effect:
Natural line width:
Fig. 9: spectrum of low-pressure mecury bulb[Wiki NLW, 2014]
Fig. 10:Gauß-Voigt profile with underlying natural line width[Meschede, 2007]
Spectroscopy
Broadening mechanisms [Meschede, 2007]
Quantum Optics and Nanophotonics Atomic Clocks Peter Deiml 10
Spectroscopy
Broadening mechanisms [Meschede, 2007]
Fig. 11: Scheme of spectroscopy experiment[Wiki TOF, 2014]
Other broadening mechanisms [Audoin et al., 2006]
Time-of-flight (TOF) broadening [Meschede, 2007]
Quantum Optics and Nanophotonics Atomic Clocks Peter Deiml 11
Ramsey-Spectroscopy
Young‘s double slit (Position space):
Fig. 12: Scheme of Young‘s double slit [Wiki YDS, 2014] Fig. 13: Distribution of intensity [Wiki YDS,2014]
Quantum Optics and Nanophotonics Atomic Clocks Peter Deiml 12
Ramsey-Spectroscopy
Fig. 14: Scheme of Ramsey-spectroscopy
Fig. 15: See frame 11
Quantum Optics and Nanophotonics Atomic Clocks Peter Deiml 13
Caesium beam clockCaesium beam tube [Bauch, 2003],[Audoin et
al., 2006]
Fig. 16: Scheme of the magnetically deflected caesium beam tube [Bauch, 2003]
• Analyzer deflects F = 4 atoms towards detector
Quantum Optics and Nanophotonics Atomic Clocks Peter Deiml 14
Caesium beam clockThe CS2 clock at the Physikalisch Technische
Bundesanstalt (PTB)
Fig. 17 : Vertical section of the vacuum chamber of PTB‘s primary clock CS2[Bauch, 2003]
Fig. 18: See frame 13
Quantum Optics and Nanophotonics Atomic Clocks Peter Deiml 15
Caesium beam clockFunction of Polarizer/Analyzer [Audoin et al.,
2006]
Fig. 19: Energy of the hyperfine levels via the magentic flux density [Audoin et al., 2006]
Quantum Optics and Nanophotonics Atomic Clocks Peter Deiml 16
Caesium beam clock
C field inside the cavity [Riehle, 2004]
Fig. 20: See frame 12
Quantum Optics and Nanophotonics Atomic Clocks Peter Deiml 17
Caesium beam clockFrequency response of a caesium beam tube [Audoin et
al., 2006]
Fig. 21: Scheme of the resonance of the central part [Bauch, 2003]
Quantum Optics and Nanophotonics Atomic Clocks Peter Deiml 18
Caesium beam clockFrequency response of a caesium beam tube
[Audoin et al., 2006]
Fig. 22: See frame 17
Quantum Optics and Nanophotonics Atomic Clocks Peter Deiml 19
Laser cooling [Weyers et al., 1999]
Fig. 23: Order of laser beams, their polarisation in an optical molasse [Weyers et al., 1999]
Fig. 24: Order of laser beams, their polarisation in a magneto-optical trap [Weyers et al., 1999]
Quantum Optics and Nanophotonics Atomic Clocks Peter Deiml 20
Caesium fountain clock
General structure [Weyers et al., 1999]
Fig. 25: Simplified setup of the atomic fountain clock [Wynands et al., 2005]
• Only one interaction zone is needed
• State-selection, Ramsey cavity and C-field analogeously to caesium beam clock
• Different detection method with lasers
• Difference: Preparation of F = 4 atoms
• Charge of magneto-optical trap
Quantum Optics and Nanophotonics Atomic Clocks Peter Deiml 21
Caesium fountain clocksResults of caesium fountain clock [Weyers et
al., 1999]
Fountain clocks more precise than beam clocks
Figure 21 (CSF1):
Quantum Optics and Nanophotonics Atomic Clocks Peter Deiml 22
Outlook
Optical clocks
Fig. 27: Temporal development of frequency uncertainty [Udem et al.,2009]
Optical clocks need the frequency comb technology
Quantum Optics and Nanophotonics Atomic Clocks Peter Deiml 23
Take-home message
Current time standard:
• Exact definition is needed
• Definition of the second & its justification
Spectroscopy:
• Method for realization of time standard
• Broadening mechanisms
Caesium beam/fountain clock:
• General setup
• Functional principle and task of all
components
• Frequency response signal
• Fountain clock more precise than beam clock
Optical clocks:
• More precise than caesium clocks
• Frequency comb technology is nessecary
Ramsey-Spectroscopy:
• Double slit in time space
• Strong analogy to Young‘s double slit in
position space
Quantum Optics and Nanophotonics Atomic Clocks Peter Deiml 24
Thank you for your attention
and
feel free to ask questions!(after the next presentation )
Hallo
Quantum Optics and Nanophotonics Atomic Clocks Peter Deiml 25
Appendix
Detection and measurement of transition [Weyers et al., 1999]
Fig. 20: Scheme of the detection zone [Weyers et al., 1999]
• Measurement of flourescence by two detectors (photodiodes)
Quantum Optics and Nanophotonics Atomic Clocks Peter Deiml 26
References
[Audoin et al., 2006] Audoin C., Guinot B., The measurement of time, Cambridge University Press, 2001
[Bauch, 2003 ] Bauch A., Caesium Atomic Clocks: Function, Performance and Applications, Measurement Science and Technology 14, 1159-1173 (2003)
[Bauch, 2012] Bauch A., Zeitmessung in der PTB, PTB Mitteilungen 122, 2012[Bauch et al., 1998] Bauch A., Fischer B., Heindorff T., Schröder R., Performance of the PTB reconstructed
primary clock CS1 and an estimate of ist current uncertainty, Metrologia 35, 829-845, 1998[BIPD, 2006] Bureau international des poids et mesures, Organisation interfouvernementale de la
Convention du Mètre. Le Système international d‘unités, 8e édtion, 2006[Demtröder, 2005] Demtröder, W., Experimentalphysik 3, Atome, Moleküle und Festkörper, 3. Auflage,
Springer Verlag, Berlin, Heidelberg, New York, 2005[Einstein, 1905] Einstein A., Zur Elektrodynamik bewegter Körper, Annalen der Physik und Chemie. 17, S.
891 – 921, 1905[Fließbach, 2006] Fließbach T., Allgemeine Relativitätstheorie, Spektrum, 2006[Meschede, 2007] Meschede D., Optics, Light and Lasers, Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim,
2007[PTB 1] Physikalisch-Technische Bundesanstalt, Wie funktioniert eine Atomuhr?
[PTB 2] Physikalisch-Technische Bundesanstalt, Optische Atomuhren
Quantum Optics and Nanophotonics Atomic Clocks Peter Deiml 27
References
[Riehle, 2004] Riehle F. Frequency Standards: Basics and Applications, Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim, 2006
[Udem et al., 2009] Udem T., Holzwarth R., Hänsch T. W., Femtosecond optical frequency combs, European Journal of Physics – Special Topis 172,69-79, 2009
[Weyers et al., 1999] Weyers S., Griebsch D., Hübner U., Schröder R., Tamm C., Bauch A., Die neue Caesiumfontäne der PTB, PTB-Mitteilungen 109, 483-491, 1999
[Wynands et al., 2005] Wynands R., Weyers S., Atomic fountain clocks, Metrologia 42, 64-79, 2005
Quantum Optics and Nanophotonics Atomic Clocks Peter Deiml 28
Web references[Wiki SR, 2014] http://en.wikipedia.org/wiki/Special_relativity, 02.05.2014[Wiki GPS, 2014] http://de.wikipedia.org/wiki/Global_Positioning_System, 02.05.2014[Wiki SC, 2014] http://de.wikipedia.org/wiki/Bahnhofsuhr, 02.05.2014[Wiki MBD, 2014] http://en.wikipedia.org/wiki/Maxwell%E2%80%93Boltzmann_distribution, 02.05.2014[Wiki SpC, 2014] http://en.wikipedia.org/wiki/Spectroscopy, 02.05.2014[Wiki NLW, 2014] http://de.wikipedia.org/wiki/Linienbreite, 02.05.2014[Wiki TOF, 2014] http://de.wikipedia.org/wiki/Flugzeitverbreiterung, 02.05.2014[Wiki YDS, 2014] http://de.wikipedia.org/wiki/Doppelspaltexperiment, 09.05.2014[SeaSky, 2014] http://www.seasky.org/solar-system/solar-system.html, 18.05.2014[Spiegel, 2013]http://www.spiegel.de/wissenschaft/technik/zeitmessung-physiker-bauen-zuverlaessigste-uhr-aller-zeiten-a-917409.html, 18.05.2014