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
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
The last 600 years of time measurement
Christiaan Huygens(1629 – 1695)
Firs
t at
omic
clo
ck a
t NPL
(195
7)
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 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
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 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.
Hiperfine structure
Ground state
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
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
kH0 0HConstant magnetic field
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
kH0 0HConstant magnetic field
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
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
Doppler CoolingA two quantum states model
Tiempo y Frecuencia
Doppler limit
»2
BDopplerkT
Cesio-133K124
Sodio K240h » 6,610-34 Js kB » 1,310-23
J/K
Doppler CoolingA two quantum states model
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
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
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
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!!
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.
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