Navigation, Gravitation and Navigation, Gravitation and Navigation, - - PowerPoint PPT Presentation

Atom Atom Atom Atom Interferometry Interferometry Interferometry Interferometry Group Group Group Group Stanford Center for Position, Navigation and Time Stanford Center for Position, Navigation and Time Stanford Center for Position, Navigation and Time Stanford Center for Position, Navigation and Time Mark Kasevich Mark Kasevich Mark Kasevich Mark Kasevich

W.W. Hansen Experimental Physics Laboratory, Stanford, CA 94305

Navigation, Gravitation and Navigation, Gravitation and Navigation, Gravitation and Navigation, Gravitation and Cosmology with Cold Atom Sensors Cosmology with Cold Atom Sensors Cosmology with Cold Atom Sensors Cosmology with Cold Atom Sensors

GGI,2006

deBroglie wavesensors

Gravity/Accelerations g

(longer de Broglie wavelength)

As atom climbs gravitational potential, velocity decreases and wavelength increases A Rotations Sagnac effect for de Broglie waves

CurrentgroundbasedexperimentswithatomicCs: wavepacket spatialseparation~1cm,phaseshiftresolution~10–5 rad

GGI,2006

Resonanttraveling waveoptical excitation, (wavelengthλ)

(Light)pulse)atominterferometry

2)levelatom

|2〉 〉 〉 〉 |1〉 〉 〉 〉

• Momentumconservationbetween

atomandlaserlightfield(recoil effects)leadstospatialseparation

• fatomicwavepackets.

GGI,2006

EnablingScience:LaserCooling

• Laserlightis

usedtocool atomicvaporsto temperaturesof ~10)6 degK.

GGI,2006

Laboratorygyroscope

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• µ

µ µ µ

• µ

µ µ µ ! "

GGI,2006

Laboratorygravitygradiometer

#$

#

• τ(s)

102 103 104

σy(τ)

10-3 10-2 10-1

Demonstrateddifferential accelerationsensitivity: 4x10)9 g/Hz1/2 (2.8x10)9 g/Hz1/2 per accelerometer)

• "

GGI,2006

GravityGradiometer:MeasurementofG

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&δ δ δ δ &'()*

Yale,2002(Fixler PhDthesis)

• Source:Proc.IEEE/Workshopon

AutonomousUnderwaterVehicles

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&' %

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µ ! "#$$% &' %

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Navigationperformance

Determinegeo)located platformpath. Necessarilyinvolvesgeodetic inputs

Simulatednavigationsolutions. 5m/hrsystemdriftdemonstrated.

+%$,%$%

Multi)functionsensormeasures gravitygradient,rotationand linearaccelerationalongasingle inputaxis. Interiorview Lasersystem

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GGI,2006

NextgenerationintegratedINS/GPS

` ` C o r d in a te tr a n s la to r IM U K a lm a n F ilte r c lo c k ` ` `` b e a m s te e rin g a n te n n a ` ` p a ra lle l c o rre la to r b a n k c h ip s c a le a to m ic c lo c k a to m ic in e rtia l m e a s u re m e n t u n its g e n e ra liz e d K a lm a n filte r s a te llite n a v ig a tio n s ig n a ls

G e n e r a liz e d V e c to r D e la y L o c k T r a c k in g N a v ig a tio n S y s te m In te g r a tio n o f R F s a te llite , in e r tia l, a n d c lo c k s e n s o r s in to o n e q u a s i-o p tim a l N a v ig a tio n , A ttitu d e , T im e e s tim a to r

Atomicphysics contributions &+$(,' $-(.&/

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Accelerometersensitivity:10)13 g/Hz1/2 − Longfree)falltimesinorbit Measurementbaseline − 100m(Spacestation) − 100km(Satelliteconstellation) Sensitivity: − 10)4 E/Hz1/2 (SpaceStation) − 10)7 E/Hz1/2 (Satelliteconstellation)

300km 100m– 100km

Earth Accelerometers

http://www.esa.int/export/esaLP/goce.html

GOCEmission,4x10)3 E

8<-,0$

Co-falling 85Rb and 87Rb ensembles

Evaporatively cool to < 1 µK to enforce tight control over kinematic degrees of freedom

Statistical sensitivity

δg ~ 10-15 with 1 month data collection

Systematic uncertainty

δg ~ 10-16 limited by magnetic field inhomogeneities and gravity anomalies. Also, new tests of General Relativity

10 m 10matomdroptower.

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8=

Usestandardmethodsto analyzespuriousphaseshifts fromuncontrolled:

• Rotations
• Gravity

anomalies/gradients

• Magneticfields
• Proof)massoverlap
• Misalignments
• Finitepulseeffects

Knownsystematiceffects appearcontrollableattheδg~ 10)16 level. [δG/G~10)5isfeasible(limited bytestmass)]

8<-,0$2

10matomdroptower.

Atomicsource

3,

Light)pulseinterferometer phaseshiftsfor Schwarzchild metric:

• Geodesicpropagation

foratomsandlight.

• Pathintegral

formulationtoobtain quantumphases.

• Atom)fieldinteraction

atintersectionoflaser andatomgeodesics.

Priorwork,deBroglie interferometry:Post)Newtonianeffectsofgravityonquantum interferometry,ShigeruWajima,MasumiKasai,Toshifumi Futamase,Phys.Rev.D,55, 1997;Bordé,etal.

()* Ground)basedprecision testsofpost)Newtonian gravity.

FromWeinberg,Eq.9.2.1

$0,1

3-&0&>2.%

Calculatedphaseshiftsfor' ,10m,apparatus.

• Analysisindicatesthatseveral

post)Newtoniantermsare comfortablywithinapparatus reach.

• In)line,accelerometer,

configuration(milliarcsec linkto externalframeNOTreq’d).

• NewconstraintsofPPN

parameters.

• Identificationofmost)promising

space)basedtests. + * ,'- ./-01#

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@ "ds2 = dt2 – a(t)2(dx2+dy2+dz2) @ =AB>* C" 23 4''+! 5'*6!* 7

Giulini,gr)qc/0602098

FromMTW + * ,'- ./-01#

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Thanks

– ToddGustavson,ResearchScientist – BorisDubetsky,ResearchScientist – ToddKawakami,Post)doctoralfellow – Romain Long,Post)doctoralfellow – Olaf Mandel,Post)doctoralfellow – PeterHommelhoff,Post)doctoralfellow – AriTuchman,Researchscientist – CatherineKealhoffer,Graduatestudent,Physics – WeiLi,Graduatestudent,Physics – Hui)ChunChen,Graduatestudent,AppliedPhysics – Ruquan Wang,Graduatestudent,Physics – Mingchang Liu,Graduatestudent,Physics – KenTakase,Graduatestudent,Physics – GrantBiedermann,Graduatestudent,Physics – XinanWu,Graduatestudent,Appliedphysics – Jongmin Lee,Graduatestudent,Electricalengineering – Chetan Mahadeswaraswamy,Graduatestudent,Mechanicalengineering – DavidJohnson,Graduatestudent,Aero/Astro engineering – Geert Vrijsen,Graduatestudent,Appliedphysics – JasonHogan,Graduatestudent,Physics – NickCiczek,Graduatestudent,AppliedPhysics – MikeMinar,Graduatestudent,AppliedPhysics – SeanRoy,Graduatestudent,Physics – LarryNovak,Seniorassemblytechnician – PaulBayer,Optomechanical engineer