Lecture 3Applications of Ultra-stable Clocks

Lecture 3Lecture 3Applications of UltraApplications of Ultra--stable Clocksstable Clocks

C. SalomonLaboratoire Kastler Brossel, Ecole Normale Supérieure, Paris

BIPM Summer school, July 25, 2003

OutlineOutlineOutline

1) Cesium versus Rubidium fountain clocks

2) Frequency measurements in the optical domain

Femtosecond laser

3) Search for variations of fundamental constants

4) Beyond fountains

New types of clocks, clocks in space

5) Perspectives

A serious limit in Cesium fountains:Collisional Frequency Shift

A serious limit in Cesium fountains:A serious limit in Cesium fountains:CollisionalCollisional FrequencyFrequency Shift Shift

Fit : y=-8.4 10-21 x

Detected Atoms0 2e+5 4e+5 6e+5 8e+5 1e+6

Rel

ativ

e Fr

eque

ncy

Shift

(10-

16)

-120

-100

-80

-60

-40

-20

0

20

September 1999January 2000

Fit : y=-8.4 10-21 xUncertainty on the slope < 10%

Shift proportional to density n, hence to number of detected atoms NatWith Cs, extrapolation to Nat = 0 is necessaryDensity is prop. to Nat only if volume remains constant

A new method to measure the collisional shift at 1% level: rapid adiabatic passage.

The ratio of density is 1/2 with a 1% accuracy(Pereira Dos Santos et al., PRL 2002)The method can reach a 0.1% accuracy

BNM-SYRTE 87Rb fountainBNMBNM--SYRTESYRTE 8787RbRb fountainfountain

Based on 8787RbRb BEC measurements,theoreticians predicted in 1997 that shift in Rb was 15 times smaller than in Cs

Measurement frequency resolution : 4 ×10-16

The 87Rb shift is ∼70 times smaller than in 133Cs

YALE

SYRTE

Collisional Shift in F=1,mF=0 : 87Rb vs 133CsCollisionalCollisional Shift in F=1,Shift in F=1,mmFF=0 : =0 : 8787RbRb vsvs 133133CsCs

Applications of atomic clocksApplications ofApplications of atomic clocksatomic clocks�Navigation, Positioning

GPS, GLONASS, deep space probes�Geodesy�Datation of millisecond pulsars�VLBI�Synchronisation of distant clocks

TAI�Fundamental physics tests Ex : general relativity

Einstein effect, gravitational red-shift : 10-4 10-6

Shapiro delay : 10-3 10-7

Search for a drift of the fine structure constant α :

α α− −d / d t a t / y e a r1 1 61 0

Frequency Comparison NIST F1 - CSF1

(period of overlap, date of measurement)

Number of Measurement0 1 2 3 4

1015

x y(F

1 - C

SF1)

-6

-4

-2

0

2

4

(15 days, August 2000)

(10 days, July 2001) (20 days, November 2001)

Long distance comparison between PTB and NIST Cesium Fountains

Long distance comparison between Long distance comparison between PTB and NIST Cesium FountainsPTB and NIST Cesium Fountains

BIPM circular Tdata base of clock comparisonsusing GPS or TWSTFT

A transportable cold atom clockA transportable cold atom clockA transportable cold atom clock

Mai 1997

PHARAO in parabolic flights in ZeroG Airbus

PHARAO PHARAO inin parabolic flights parabolic flights in in ZeroG AirbusZeroG Airbus

PHARAO: a Transportable FountainPHARAO: a Transportable PHARAO: a Transportable FountainFountain

vacuum chamber

atomic hydrogenFaraday cage

time resolvedphoton counting

2S detector

cryostat

chopper

dye laser486 nm

microwaveinteraction

cold atomsource

detection70 fs Ti:sapphiremode locked laser

1/2 x f dye

λ

I

9.2 GHz

4/7 x f dye

f dye

243 nm

x1/2x4/7

x 2 ν1S-2S = 2 466 061 413 187 103 (46) HzAccuracy : 1.8 10-14

Measurement of 1S-2S transition of Hydrogen at Max Planck Institut fürQuantenoptik in Garching

M. Niering et al, P.R.L. 85, June 2000

Multiplication by 250 000 of the cesium frequency to theUV range, 243 nm

�Pulsed laser, �repetition rate: 840 MHz

J. Reichert et al. PRL 84, 3232 (2000),S. Diddams et al. PRL 84,5102 (2000)A. Brusch , D.B. Kolker, G.D. Rovera

Femtosecond LaserFemtosecond Laser

atν

atν

nn-1 n+1ν=0

νOffset

bn f rep

f rep = 840 MHz

offsetrepat fnb νν ++=

Frequency combFrequency comb

1) Bring νoffset to 02) Use fountain clock to drive the rep. rate

Einstein Equivalence Principle and the stability of fundamental constants

Einstein Equivalence Principle Einstein Equivalence Principle and the stabilityand the stability ofof fundamentalfundamental constantsconstants

It implies the stability of fundamental constants: α=e2/hc, me, mp,�In particular: the ratio of the transition frequencies in different atoms andmolecules should not vary with space and timeThe EEP can be tested by high resolution frequencymeasurements regardless of any theoretical assumption

EEP revisited by modern theories: gµν ⇒ gµν,ϕ,�Fundamental constants depend upon local value of ϕ : α(ϕ), m(ϕ),�

EEP EEP ensuresensures thethe universalityuniversality of of thethe definitiondefinition of of thethe secondsecond

Violations of EEP are expected at some level !!For instance: T. Damour, G. Veneziano, PRL 2002

In any free falling local reference frame, the result of a non gravitational measurement should not depend upon when it is performed and where it is performed.

Does the fine structure constant α varies with time ?Does the fine structure constant Does the fine structure constant αα varies with time ?varies with time ?

Because of large relativistic corrections, the hyperfine energy of an alkali atom depends upon Z and α=e2/ħc

Search method for α drift:

Compare hyperfine energy of rubidium and cesium as function of time

� Oklo test : geochemical analysis of the natural fossil fission reactor in Oklo (Gabon, 1.8×109 yr ago) :

Damour, Poliakov, Nucl. Phys. B 480, 37 (1996)� Absorption spectroscopy from quasars:

J. Webb et al., PRL 87, 091301 (2001)

( ) )5.35.0(1018.072.0 5 <<×±−=∆ − zαα

7101 −×≤− Oklonow αα 117105 −−×≤ yrαα&

Present tests of cosmological Variations of α

Present tests of cosmological Present tests of cosmological Variations of Variations of αα

� A priori loss of factor 1010 in sensitivity !!� ~ 1 year versus 1010 years� But: � ultra-stable and accurate clocks:� 10-15 !10-16 -10-17

� repeatable measurements� independent checks in various labs� choice of hyperfine, fine and optical transitions

Laboratory tests versus cosmological tests

Laboratory tests versus Laboratory tests versus cosmological testscosmological tests

See S. Karshenboim, Can. J. Phys 78 639, (2000), J.P. Uzan (2002)

87Rb -133Cs Comparison over 5 years87Rb -133Cs Comparison over 5 years

( ) 16ln 0.2 7 10 /Rb

Cs

d υ yeardt υ

− = ± ×

( ) 160.4 16 10 / yearαα

−= − ± ×&Within Prestage et al.

theoretical framework :

( ) Hz123359046106828346 .υRb =

H. Marion et al.,PRL (2003)

1997 1998 1999 2000 2001 2002 2003 2004

-20

-15

-10

-5

0

5

10

Rel

ativ

e fre

quen

cy (1

0-15 )

Year

� Clock quality: ν0T

� Increase clock frequency: optical clocks� Increase interrogation time

� Trapping atoms� microgravity in a satellite:� PHARAO project, ESA-CNES, BNM-SYRTE, ENS, ON� PARCS project: NIST, JPL, NASA� RACE project: Penn ST., JPL, NASA

Beyond fountainsBeyond fountainsBeyond fountains

Toward an optical cold atom clockCold Strontium Atoms

P. Lemonde, I. Courtillot, A. Quessada, R. Kovacich, BNM-SYRTE λ = 689 nm

Towards an optical clockwith cold strontium atomsTowardsTowards an opticalan optical clockclockwith coldwith cold strontium strontium atomsatoms

03P12

461 nm(32 MHz)

689 nm(7.6 kHz)

671 nm(10-5 Hz)

698 nm(87Sr: 1 mHz)

1S0

1P1

I. Courtillot, A. Quessada, R. Kovacich, A. Brusch, D. Kolker, J. J. Zondy, G. Rovera, and P. LemondearXiv:physics/0303023

Towards an optical clock with fermionic Strontium : 87Sr

Towards an optical clock with fermionic Strontium : 87Sr

� Method: (H. Katori)Interrogate atoms in optical lattice without frequency shift

� Long interaction time� Large atom number (108)� Lamb-Dicke regime

Excellent frequency stability

� Small frequency shifts:� No collisions (fermion)� No recoil effect (confinement below optical wavelength)� Small Zeeman shifts (only nuclear magnetic moments)�

87Sr optical clock 87Sr optical clock

Space ClocksSpace ClocksSpace Clocks

ESA, CNES, SYRTE NASA, JPL, NIST

Atomic Clock in SpaceAtomic ClockAtomic Clock inin SpaceSpace

� Thermal beam : v = 100 m/s, T = 5 ms ∆ν = 100 Hz

� Fountain : v = 4 m/s, T = 0.5 s ∆ν = 1 Hz

� PHARAO : v = 0.05 m/s, T = 5 s ∆ν = 0.1 Hz

Cesium reservoir

Cooling zoneRamsey Interrogation

detection

Selection

Microwave cavity

Ion pump3 Magnetic shields and solenoids

PHARAO cold atom clockPHARAO cold atom clockPHARAO cold atom clock

Fountain : v = 4 m/s, T = 0.5 s ∆ν = 1 Hz

� PHARAO : v = 0.05 m/s, T = 5 s ∆ν = 0.1 Hz

Mass 91 kgPower 110 WL=1m

ACES: Atomic Clocks Ensemble in SpaceACES: Atomic Clocks Ensemble in Space

PHARAO H-MASER

� A cold atom Cs standard in space� Worldwide access� Fundamental physics tests

−

−= 212

1

2 1cUU

νν

( ) 102 1070 −×≈

=chUTerre

A Prediction of General RelativityA A PredictionPrediction ofof GeneralGeneral RelativityRelativity

Redshift measurement at 7 10-5: R. Vessot et al., 1976

Relativity tests on ISSRelativityRelativity tests on ISStests on ISS

( ) ( )2 21 1S E

E E

U gHc c

ν ν ν α αν ν− ∆ ∆

= = + = +

Red shiftComparaison of absolute frequencies of space clock ςS

and ground clock ςE

Factor 25 improvement

Second order Doppler effect: -1/2 v2 / c2 = 3 10-10

Einstein : α = 0 at 7 10-5 (Vessot, Levine 76)At Η = 450kms :∆ς /ς = + 4.59 10-11

With clock accuracy of 10-16, the red-shift can be measured at 3 10-6

ACES on the ISSACES ACES onon thethe ISSISS

ACES ON COLUMBUS EXTERNAL PLATFORM

ACES ON COLUMBUS EXTERNAL ACES ON COLUMBUS EXTERNAL PLATFORMPLATFORM

M = 227 kg P = 450 W

Launch date : end of 2006Mission duration : 18 months

ACES

Atomic ClockEnsemble in Space

Atomic ClockEnsemble in Space

PHARAO : Cold Atom Clock in Space. CNES (France)A. Clairon, P. Laurent, P. Lemonde, M. Abgrall, S. Zhang, C. Mandache, F. Allard, M. Maximovic, F. Pereira,G. Santarelli, Y. Sortais, S. Bize, P. Rosenbusch, H. Marion, D. Calonico, N. Dimarcq, (BNM-SYRTE),C. Salomon (ENS)SHM : Space Hydrogen Maser. ON (Switzerland)A. Jornod, D. Goujon, L.G. Bernier, P. ThomannMWL : Microwave link. Kayser-Threde-Timetech (Germany)W. Schaefer, S. Bedrich, S. Fockersperger, F. Huber ACES payload: AstriumACES is open to any interested scientific userW. Knabe, P. Wolf, L. Blanchet, P. Teyssandier, P. Uhrich, A. SpalliciNew members :2001: UWA (Australia), A. Luiten, M. Tobar, J. Hartnett, C. Locke, R. Kovacich2002: LENS (Italy), G. Tino, G. Ferrari, L. CaciapuottiESA: MSMS. Feltham, F. Reina, I. Aguilar-Sanchez CNES:C. Sirmain + team of 20 engineers at CST, Toulouse

Perspectives (1) Microwave Clocks Perspectives (1)Perspectives (1) Microwave Clocks Microwave Clocks Rubidium fountains have the potential to surpass Cesium by one order of magnitude: Cs: stability 10-16 per day, accuracy: ~ 2 10-16

Rb: a few 10-17 with cryogenic local oscillator

Comparisons between distant clocks at 10-16 using ACES in 2006Currently, clock transport !!

Or major improvements of microwave and optical links

Wide domain of applicationsFundamental physics, navigation, geodesy, Time and frequencymetrologyClocks with entangled states ? Demonstrated with two ions at NISTStability as 1/N instead of 1/N1/2

Clocks of the future < 10-17ClocksClocks ofof thethe future < 10future < 10--1717

� Q= ν/∆ν= 2 ν T� Increase the frequency: optical clocks� Neutral atoms: Ca, Sr, Mg, Ag, �

better performance in space� Trapped ions : Hg+, In+, Yb+ �� In both cases: � Ultra-stable lasers with emission linewidth << 1 Hz,

B. Young et al., PRL 82, 3799 (1999)

� Frequency comb with femtosecond laser � connects the microwave domain to visible domain

with a simple deviceLarge improvement of tests of variations of α, gp, Me/ Mp

Laboratory tests of α variations using clocksLaboratoryLaboratory tests of tests of αα variations variations using clocksusing clocksRelativistic corrections : the energy levels of the frequencies of two different alkalis depend on α and Z1, Z2

The ratio of the hyperfine energies of different atomic species explicitely depends on α=e2/ħc

Hg+ vs H : Prestage et al., PRL 74, 3511 (1995)

( ) ( )[ ]αα

αααα

υυ &&

×=×−=

2112

1

2 ,,ln KZFLZFLdtd

reldreld

The twin fountain Cs-RbThe twin fountain CsThe twin fountain Cs--RbRb

Simultaneous operation With Cs and RbBetter test over αTarget: dα/dt at 10-16/year