Centro Nacional de Metrología, CENAM, km 4.5 Carretera a los Cues, El Marques, Qro., J. Mauricio López R.

Albert Einstein

The heart as the closest clock of men

Slaves of our past and of the time

TIME The most measured physical quantity THE TWO FACES OF TIME MEASUREMENT The current SI Time is the most accurate measurement Scientific and fundamental researchTechnological and practical applications

Dennis D. McCarty, Evolution of Time Scales from astronomy to physicasl metrology, Metrologia 48 (2011), S132 – S144. The last 600 years of time measurement

Christiaan Huygens (1660) Accurate pendulum clock and the equation of time The last 600 years of time measurement Christiaan Huygens (1629 – 1695)

Longitude Act of 1714 John Harrison chronometers The last 600 years of time measurement

Greenwich meridian as interational reference (1884) The last 600 years of time measurement

First atomic clock at NPL (1957) The last 600 years of time measurement Louis Essen and his NPL Cs atomic clock

Atomic definition of the second, 1967 The last 600 years of time measurement The second is the duration of periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the Cesium 133 atom. Resolution 1, 13th CGPM, 1967

Atomic clocks era The last 600 years of time measurement Progress at one order of magnitud per decade

Ultracold matter and Cs fountain clocks The last 600 years of time measurement Progress at one order of magnitud per decade

Frequency combs and optical atomic clocks The last 600 years of time measurement Progress about four orders of magnitud per decade !!

Cs-133 Atomic Clocks The second is the duration of periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the Cesium 133 atom. Hiperfine structure Ground state

What is an atomic clock

Disciplined oscillators The basic concept of an atomic/optical clock  AA LL L LL L L  

Frequency Stability of an Atomic Clock o  Allan Deviation

Strategies to develop better atomic clocks Cold atoms and very long lifetime on excited states Optical Frequencies Large amount of atoms Large averaging times / robust systems

Nuclear Magnetic Resonance and atomic clocks

Spin invertion by the action of a rotating magnetic field Rabi´s Method z Constant magnetic field Larmour Frequency 00 

Spin invertion by the action of a rotating magnetic field Rabi´s Method z Constant magnetic field Larmour Frequency 00  Rotating magnetic field perpendicular to H 0 

Spin invertion by the action of a pulsed rotating magnetic field Ramsey´s Method z Constant magnetic field Larmour Frequency 00  Rotating magnetic field perpendicular to H 0 Pulsed! 

CampoMagnético Constante (Campo C) Contenedor con Cesio 133 Cavidad de Ramsey Campo Magnético Inhomogéneo (Campo B) Campo Magnético Inhomogéneo (Campo A) Filamento Incandescente (Ionizador) Detector Generador de Microondas Lazo de amarre Vacío Ramsey Method

First atomic clocks (1957)

Commercial available Cs atomic clock using the magnetic selection of N. Ramsey

Cs-133 Optical pumping Coulomb  850nm Spin-Spin GHz F’=5 F’=4 F’=3 F’=2 F’=4 F’=3 F’=4 F’=3 251MHz 200MHz 150MHz 1167MHz + Zeeman Effect 11 sublevels 9 sublevels 7 sublevels 5 sublevels 9 sublevels 7 sublevels 9 sublevels 7 sublevels + INTERACTION ENERGY Spin-Orbit 6 2 P 3/2 6 2 P 1/2 6 2 S 1/2  100GHz  894nm + Not at scale

Ramsey method with optical pumping (1985) Cs Oven Pumping Laser Detection Laser Detector Ramsey Cavity Microwave Oscillator Phase lock loop

Optically pumped thermal Cs beam clock CENAM CsOp Hz

Doppler Cooling A two quantum states model Energy E2E2 E1E1 Laboratory reference frame F = 0 -  0 v

R = F + k·v + …  0 L = F - k·v + …<< 0 Atom´s reference frame 0 Doppler Cooling A two quantum states model

Doppler limit Cesio-133 Sodio h  6,6  J  s k B  1,3  J/K Doppler Cooling A two quantum states model

Phys. Rev. Lett. 61, 169–172 (1988) [Issue 2 – 11 July 1988 ] Observation of atoms laser cooled below the Doppler limit Paul D. Lett, Richard N. Watts, Christoph I. Westbrook, and William D. Phillips Electricity Division, National Bureau of Standards, Gaithersburg, Maryland Phillip L. Gould Department of Physics, University of Connecticut, Storrs, Connecticut Harold J. Metcalf Department of Physics, State University of New York at Stony Brook, Stony Brook, New York Received 18 April 1988 We have measured the temperature of a gas of sodium atoms released from ``optical molasses'' to be as low as 43±20 µK. Surprisingly, this strongly violates the generally accepted theory of Doppler cooling which predicts a limit of 240 µK. To determine the temperature we used several complementary measurements of the ballistic motion of atoms released from the molasses. ©1988 The American Physical Society

F=4 F´=5  852 nm Energy The Cs-133 atom as a two level quantum system

F=4 F´=5 m = +4 m = -4 m = 0 m = -5 m = +5 m = 0  852 nm 0 1 B / Gauss Not at escale Energy The Cs-133 atom as a multilevel quantum systems

Temperatures below the Doppler limit x 0 44 22 linear -- ++ -- z y m = -3/2 m = -1/2m = +1/2 m = +3/2 m = -1/2 m = +1/2 J = 1/2 J = 3/2

Stark effect g-½g-½ g+½g+½ 0 linear -- ++ -- Energy Position 88 z 0 443838 2238385858

z Energy 88 443838 22 5858 g-½g-½ g+½g+½ Sisyphus effect and temperatures below the Doppler limit

Frequnecy  E  t  h/4    t  1/4    1Hz 0  Hz  /  Transition probability 0  Ramsey Method + ultracold Cs atoms

Cooling beams Detection laser Microwaves cavity Detector Optical molases Wayne M. Itano, Norman F. Ramsey, Accurate Measurement of Time, Scientific American, July Cs Fountain Clock (1990)

Resolution of the peak Wayne M. Itano, Norman F. Ramsey, Accurate Measurement of Time, Scientific American, Clock transition

33.0 cm22.0 cm 35.0 cm CENAM CsF-1 physical package

Cesium fountain clock CENAM CsF-1 MOT Optical systemPhysics package

TIME IS THE MOST POWERFUL METROLOGICAL VARIABLE JOHN HALL, Nobel Prize in Physics 2005

NO CONTABAN CON MI ASTUCIA!!

Centro Nacional de Metrología, CENAM, km 4.5 Carretera a los Cues, El Marques, Qro., J. Mauricio López R.

The second is the duration of periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the Cesium 133 atom.

Horno de Cs Láser de bombeo Láser de detección Detector Cavidad de microondas CENAM thermal Cesium beam atomic clock 180 Hz

Rabi pedestal comparison between CENAM CsOP-1 and CENAM CsOP-2 Ramsey fringe line comparison between CENAM CsOP-1 and CENAM CsOP-2.

Cooling beams Detection laser Microwave cavity Detector Optical molases CENAM Cs Fountain Clock CENAM CsF-1  600 nk

33.0 cm22.0 cm 35.0 cm CENAM CsF-1 physical package

CsF-1 Frecuencia Probabilidad de transición CsOP-1 CsOP-2 CENAM Cesium clocks

CsF-1 Frecuencia Probabilidad de transición CsOP-1 CsOP-2 CsF-1 CENAM Cesium clocks