Diapositiva 1 - NIST

Centro Nacional de Metrología, CENAM, km 4.5 Carretera a los Cues, El Marques, Qro., www.cenan.mx

Introduction to atomic clocksJ. Mauricio López R.

CENTRO NACIONAL DE METROLOGÍA, CENAM

What is time?

Tiempo y Frecuencia

Time is what clocks measure

Tiempo y Frecuencia

Albert Einstein

Clock = Oscillator + Counter

Tiempo y Frecuencia

The heart as the closest clock of men

Clock = Oscillator + Counter

Tiempo y Frecuencia

Time measurement is the oldest measurement of humankind

nearly 5000 years old

Tiempo y Frecuencia

The second, the most anthropometric unit

Slaves of our past and of the time

In clocks are resumed our civilization deepest past and our best science

Tiempo y Frecuencia

TIMEThe most measured physical quantity

THE TWO FACES OF TIME MEASUREMENT

The current SITime is the most accurate measurement

Scientific and fundamental research Technological 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

Tiempo y Frecuencia

Chris

tiaan

Huy

gens

(166

0)

Accurate pendulum clock and the equation of time


Christiaan Huygens(1629 – 1695)

Long

itude

Act

of 1

714

John Harrison chronometers


Gree

nwic

h m

erid

ian

as

inte

ratio

nal r

efer

ence

(188

4)


Firs

t at

omic

clo

ck a

t NPL

(195

7)


Louis Essen and his NPL Cs atomic clock

Atomic definition of the second, 1967


The second is the duration of 9 192 631 770 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

Atom

ic cl

ocks

era


Progress at one order of magnitud per decade

Ultracold matter and Cs fountain clocks


Progress at one order of magnitud per decade

Frequency combs and optical atomic

clocks


Progress about four orders of magnitud per decade !!

The base units of the International System of units

Tiempo y Frecuencia

Cs-133 Atomic Clocks


Hiperfine structure

Ground state

Tiempo y Frecuencia

What is an atomic clock

Tiempo y Frecuencia

Disciplined oscillatorsThe basic concept of an atomic/optical clock

nn0

dnAdnL

nL

dnL

nL

nL » n0

Tiempo y Frecuencia

nn

Ny1)(

0

»

Frequency Stability of an Atomic Clock

-15 -10 -5 0 5 10 15

trans

ition

pro

babi

lity

0

1

no

n

)( y

Allan Deviation Tiempo y Frecuencia

Strategies to develop better atomic clocks

1N

0n0n

Cold atoms and very long lifetime on excited states

Optical Frequencies

Large amount of atoms

Large averaging times / robust systems

01)(1

00 0

»

nnn

nN

y N

StabilityPerfecty :0)(

Tiempo y Frecuencia

Nuclear Magnetic Resonance and atomic clocks

Tiempo y Frecuencia

Spin invertion by the action of a rotating magnetic field Rabi´s Method

z

kH0 0HConstant magnetic field

Larmour Frequency

JH

002 0

0

Tiempo y Frecuencia

Spin invertion by the action of a rotating magnetic field Rabi´s Method

z


Larmour Frequency

JH

002 0

0

)cos(sin11 jiH ttH

Rotating magnetic field perpendicular to H0

Spin invertion by the action of a pulsed rotating magnetic field Ramsey´s Method

z


Larmour Frequency

JH

002 0

0

)cos(sin11 jiH ttH

Rotating magnetic field perpendicular to H0

Pulsed!

CampoMagnético Constante (Campo C)

Contenedor con Cesio 133

Cavidad de RamseyCampo Magnético

Inhomogéneo (Campo B)

Campo Magnético Inhomogéneo

(Campo A)

FilamentoIncandescente

(Ionizador)

Detector

Generador deMicroondas

Lazo deamarre

Vacío

Ramsey Method

First atomic clocks (1957)

Tiempo y Frecuencia

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

Tiempo y Frecuencia

Cs-133 Optical pumping

Coulomb

»85

0nm

Spin-Spin

9.192631770 GHz

F’=5F’=4F’=3F’=2

F’=4

F’=3

F’=4

F’=3

251MHz

200MHz

150MHz

1167MHz

+ Zeeman Effect

11 sublevels 9 sublevels7 sublevels5 sublevels

9 sublevels

7 sublevels

9 sublevels

7 sublevels

+

INTERACTION

ENER

GY

Spin-Orbit

62P3/2

62P1/2

62S1/2

»10

0GH

z»

894n

m

+

Not

at s

cale

Tiempo y Frecuencia

Ramsey method with optical pumping (1985)

Cs Oven

Pumping Laser Detection Laser

Detector

Ramsey Cavity

MicrowaveOscillator

Phase lockloop

Tiempo y Frecuencia

Optically pumped thermal Cs beam clock CENAM CsOp-2

9192630000 9192632000 9192634000

Inte

nsid

ad /

U.A

.

Frecuencia / Hz

180 Hz

Tiempo y Frecuencia

Doppler CoolingA two quantum states model

Ene r

gy E2

E1

012 nhEEE

Laboratory reference frame

nF=n0- nF=n0-n0

v

nR = nF + k·v + … » n0

nL= nF - k·v + …<< n0

Atom´s reference frame

n0

...22

12

20

2

00

Mch

cv

abs vk

kpF2

dtd


Tiempo y Frecuencia

Doppler limit

»2

BDopplerkT

Cesio-133K124

Sodio K240h » 6,610-34 Js kB » 1,310-23

J/K


Tiempo y Frecuencia

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 20899Phillip L. Gould Department of Physics, University of Connecticut, Storrs, Connecticut 06268Harold J. Metcalf Department of Physics, State University of New York at Stony Brook, Stony Brook, New York 11794

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

Tiempo y Frecuencia

F=4

F´=5

» 852 nmEn

ergy

The Cs-133 atom as a two level quantum system

Tiempo y Frecuencia

F=4

F´=5

m = +4

m = -4

m = 0

m = -5

m = +5

m = 0

» 852 nm

0 1B / Gauss

Not

at e

scal

e

GausskHzB

hE /100/ »

GaussMHzB

hE /5.2/ »

En

e rgy

The Cs-133 atom as a multilevel quantum systems

Temperatures below the Doppler limit

x

0 4 2

linear - + -linear linear

z

ym = -3/2 m = -1/2 m = +1/2 m = +3/2

m = -1/2 m = +1/2J = 1/2

J = 3/2

Tiempo y Frecuencia

Stark effect

g-½

g+½

0

linear - + -linear linear

Ener

gy

Position

8 z0 4 38 238 58

z

Ener

gy

8 4 38 2 58

g-½ g+½

Sisyphus effect and temperatures below the Doppler limit

Tiempo y Frecuencia

Frequnecy

E • t h/4

n • t 1/4

n » 1Hz

n0»1010Hz

dn/n »10-15

Tran

siti o

n pr

o bab

il it y

n0

n

Ramsey Method + ultracold Cs atoms

Tiempo y Frecuencia

CENT R O NACIONA L DE ME T ROL OGÍA

Cooling beams

Detection laser

Microwaves cavity Detector

Optical molases

Wayne M. Itano, Norman F. Ramsey, Accurate Measurement of Time, Scientific American, July 1993.

Cs Fountain Clock(1990)

Tiempo y Frecuencia

1615 101101 »

Resolution of the peak-1.5

-1

-0.5

0

0.5

1

1.5

0 2 4 6 8 10 12 14 16 18

Hz 1»n

Wayne M. Itano, Norman F. Ramsey, Accurate Measurement of Time, Scientific American, 1993.

-100 -80 -60 -40 -20 0 20 40 60 80 100

Clock transition

Tiempo y Frecuencia

33.0

cm

22.0

cm

35.0

cmCENAM CsF-1

physical package

Cesium fountain clock

CENAM CsF-1

MOT

Optical system Physics package

Tiempo y Frecuencia

Tiempo y Frecuencia

TIME IS THE MOST POWERFUL METROLOGICAL VARIABLEJOHN 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., www.cenan.mx

Introduction to atomic clocksJ. Mauricio López R.

CENTRO NACIONAL DE METROLOGÍA, CENAM

THANK YOU!!

Hornode Cs

Láser debombeo

Láser dedetección

Detector

Cavidad demicroondas

CENAM thermal Cesium beam atomic clock

9192630000 9192632000 9192634000

Inte

nsid

ad /

U.A

.

Frecuencia / Hz

180 Hz

CE NT RO NAC IONA L DE M ET ROLOGÍA

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

cm

22.0

cm

35.0

cmCENAM CsF-1

physical package

CE N TRO NAC IONA L DE M E TROLOGÍA

CsF-1

Frecuencia

Prob

abili

dad

de tr

ansic

ión

CsOP-1

CsOP-2

CENAM Cesium clocks

CsF-1

Frecuencia

Prob

abili

dad

de tr

ansic

ión

CsOP-1

CsOP-2

CsF-1

CENAM Cesium clocks

Diapositiva 1 - NIST

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