Frequency Tunable Atomic Magnetometer based on an Atom ... · D.A. Braje1, J.P. Davis2, C.L....

D.A. Braje1, J.P. Davis2, C.L. Adler2,3, and F.A. Narducci2

Blaubeuren Quantum Optics Summer School

29 July 2013

Frequency Tunable Atomic Magnetometer based on an Atom Interferometer

The Lincoln Laboratory portion of this work is sponsored by the Assistant Secretary of Defense for Research & Engineering under Air Force Contract #FA8721-05-C-0002. Opinions, interpretations, conclusions and recommendations are those of the authors and are not necessarily endorsed by the United States Government.

1MIT Lincoln Laboratory, Lexington, MA 2Naval Air Systems Command, Patuxent River, MD 3St. Mary’s College of Maryland, Saint Mary’s City, MD

Also thanks to S. A. DeSavage, R. Forster and

Z. Switzer

$$$$$$$$$$ ONR

NavAir CTO $$$$$$$$$$

Blaubeuren Summer School July 29, 2013

This is data

• Magnetometry / Gradiometry Motivation – Applications: Remote Sensing, Security, Biomagnetics, Navigation – Gradiometry

• Atom Interferometer Magnetometer – Atom Interferometer Concept – NMR Pulse Sequences for Atoms

• Experimental Results – Clock Transition – Ramsey vs. Hahn Echo

Outline

Blaubeuren Summer School July 29, 2013

~ fT/Hz1/2

Geomagnetic

Geology

Platform Maneuver

Swell

ASQ-208

Buffeting

P-2000

Spe

ctra

l Den

sity

(nT/

Hz

)

0.5

0.0001

0.001

0.01

0.1

1

10

0.01 0.1 1.0 10 100

MAD ELF

Frequency (Hz)

CPA=2000 ft

3x10 nT-ft Dipole

8 3

CPA=1000 ft

ELF

NIST Welch Budker Romalis

Airborne Magnetic Noise

Blaubeuren Summer School July 29, 2013

Motivation: (classical) gradiometer example

1

Distance

B-F

ield

∆B Object

∆B Noise

P2000 Gradiometer Test Memorial Airfield, Chandler AZ April 27 2003

1 2

Noise

Car

Time [hrs]

Fiel

d [n

T]

0 0.2 0.4 0.6 0.8

0.8

0

-0.8

Time [hrs]

0

-0.2

-0.4

-0.6

0 0.2 0.4 0.6 0.8

Fiel

d [n

T]

P2000 Sensors

80 ft

2

150 ft

AI Gradiometer Sensitivity: 0.2 pT/m

Even an Admiral can see this!

Sensitivity: 500 pT/(80ft)

Blaubeuren Summer School July 29, 2013

• Clocks – Frequency standards – Navigation, communication, synchronization

• Magnetometers – Magnetic anomaly detection (i.e. submarines,

unexploded ordinance, mines), detection of dangerous liquids and uranium, biomagnetics, navigation

• Accelerometers, Gyroscopes – Arrayed for differential acceleration, gravimeters, etc – Navigation, seismology, mass anomaly detection

(minerals, bunkers, natural resources) – Fundamental laws of physics

Atom Interferometry Applications

Navigation

Detection / Security

Biomagnetics

Language is common to the worlds of NMR and quantum computing

Blaubeuren Summer School July 29, 2013

Keep Sensitivity; Design Around the Noise

Rev. Sci. Instrum. 77, 101101 (2006)

Commercially-available SQUIDS

kHz Hz mHz Frequency

B-F

ield

nT

pT

fT

Shielded Room

Cannot remove magnetic noise in remote sensing

1. Filter out of band noise 2. Measure magnetic field

gradient (Gradients used for object location)

Blaubeuren Summer School July 29, 2013

• Magnetometry / Gradiometry Motivation – Applications: Remote Sensing, Security, Biomagnetics, Navigation – Gradiometry

• Atom Interferometer Magnetometer – Atom Interferometer Concept – NMR Pulse Sequences for Atoms

• Experimental Results – Clock Transition – Ramsey vs. Hahn Echo

Outline

This is data

Blaubeuren Summer School July 29, 2013

Two level atom reminder

Natural Linewidth

Powerbroadened Linewidth

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Raman Resonances Now controlled by ground state decoherence time which can be made very small

Blaubeuren Summer School July 29, 2013

Atom Interferometer: Time Domain

y

π/2 π/2 π

∆νHF |1⟩ |2⟩

|3⟩

ω1 ω2

|2⟩

|1⟩

|2⟩

|1⟩

|2⟩

|1⟩

Davis & Narducci, JMO 55 3173 (2008)

Zhou et al. PRA 82 061602 (2010)

Co-propagating Raman beams: Doppler-free

|1⟩ |2⟩

π/2 π/2

0 t |1⟩

x

( )

∂−∂−+

−−=∆

∫∫ ttBttBmgmg

gTkkT

T

T

FFFFB

2/

2/

0''

221

)()()(

µ

φ

π

T

g

Pseudospin Representation:

Blaubeuren Summer School July 29, 2013

Magnetic Gradient (spin echo) Interferometer…not quite

Blaubeuren Summer School July 29, 2013

Ramsey (π/2−π/2)

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Spin Echo (π/2−π−π/2)

Blaubeuren Summer School July 29, 2013

(Unbalanced) Spin echo (π/2−π−π/2)

Blaubeuren Summer School July 29, 2013

Atom Interferometer: Frequency Domain

π/2

|2⟩

|1⟩

π/2

|2⟩

|1⟩

|1⟩ |2⟩

π/2

0 t |1⟩

x

g(ω

) Frequency [kHz]

N = 10

π π π π Pulse sequence controls interferometer sensitivity to noise Scanning number of pulses can map out magnetic noise spectral density

−−=∆ ∫∫ ttBttBmgmg

T

T

T

FFFF δδ2

0''

B )()()(μφ

TBmgmg FFFFB )( '' −=∆

µφ

π

|2⟩

|1⟩

π π/2

T

Blaubeuren Summer School July 29, 2013

Filter Functions Frequency Domain

π/2 π/2 π π π

T = 1 ms

N = 10 N = 5

N = 1

N = 0 T = 1 ms

T/2 T/2

π/2 π/2 π

T = 1000 us

T = 500 us

T = 250 us

N = 1 Hahn Echo

N pulses

Blaubeuren Summer School July 29, 2013

State preparation well defined qubit initialization

• Gradient coils – 10 G/cm

• Trapping lasers: – Amplified (TA7613) New

Focus StableWave 7013 – 2.5 cm beam

5 2S1/2

5 2P3/2

F' = 4

F' = 3

F' = 2 F' = 1

F = 3

F = 2

Trapping Repump

Unshielded environment and in a metal canister!

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• Trapping Setup

Apparatus

• Raman Lasers

Blaubeuren Summer School July 29, 2013

ECDL

Trapping Beam

Sat Abs

+1 HWP

0

+1

MOT

AO1

AMP

Beat note

Experimental schematic

Blaubeuren Summer School July 29, 2013

Timing sequence

5 2S1/2

5 2P3/2

F' = 4

F' = 3

F' = 2 F' = 1

F = 3

F = 2

5 2S1/2

5 2P3/2

F' = 4

F' = 3

F' = 2 F' = 1

F = 3

F = 2

Readout

5 2S1/2

5 2P3/2

F' = 4

F' = 3

F' = 2 F' = 1

F = 3

F = 2

5 2S1/2

5 2P3/2

F' = 4

F' = 3

F' = 2 F' = 1

F = 3

F = 2

Time [ms]

Trapping B-Field

Repump Field

Trapping Field

EXPERIMENT

0 5 -5 -10 -15 -20

Trapping Repump Trapping Readout Raman

85Rb ~107 atoms; ~300 µK; F = 2

Well-defined coherent qubit Initialize Gate operations Readout

Blaubeuren Summer School July 29, 2013

A real atom: 85Rb

11 different Raman resonances!

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Raman spectra (arbitrary field)

5 2S1/2

5 2P3/2

F' = 4

F' = 3

F' = 2 F' = 1

F = 3

F = 2 Two photon detuning [kHz]

p3 p u l s eT

1=∆υ

11 different Raman resonances

85Rb ~107 atoms ~300 µK F = 2

Blaubeuren Summer School July 29, 2013

25

Use to “zero” field around atoms

100

120

140

160

180

200

220

-1.5 -1 -0.5 0 0.5

Current (amps)

Opt

ical

Spa

cing

40455055606570758085

0.5 0.7 0.9 1.1 1.3

Current (amps)

Opt

ical

Spa

cing

100110120130140150160170180

-0.5 -0.3 -0.1 0.1 0.3 0.5

Current (amps)

Opt

ical

Spa

cing

Field 1 Field 2

Field 3

Blaubeuren Summer School July 29, 2013

26

Single Peak

Blaubeuren Summer School July 29, 2013

Selection Rules

Blaubeuren Summer School July 29, 2013

• PQE • 03 Jan 2011

Six Peaked Spectrum

Transverse

Blaubeuren Summer School July 29, 2013

• PQE • 03 Jan 2011

Five Peaked Spectrum

Longitudinal

Blaubeuren Summer School July 29, 2013

Effect of pulse shape

Blaubeuren Summer School July 29, 2013

31

Square vs Gaussian Pulses

Square Pulse

Gaussian Pulse

Blaubeuren Summer School July 29, 2013

Hybrid Pulse

Blaubeuren Summer School July 29, 2013

• PQE • 03 Jan 2011

33

Crude Magnetometer 10 min of data @ 0.25Hz

Now can do up to 10 Hz

Blaubeuren Summer School July 29, 2013

Rabi cycling: m=0 to m'=0 transition universal gates ability to read out

TRaman Readout

TRaman [ms]

π

π/2

5 2S1/2

5 2P3/2

F' = 4

F' = 3

F' = 2 F' = 1

F = 3

F = 2

Time

pulseT1

=∆υ

Two photon detuning νHF/2

R+

R- AOM

Blaubeuren Summer School July 29, 2013

Ramsey interference

Blaubeuren Summer School July 29, 2013

• As time between pulses is lengthened, Ramsey interference disappears.

Ramsey vs. double delay T=10 µsec T=30 µsec

T=50 µsec T=70 µsec

Increasing T

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Atom Interferometer Clock Transition

T

Two-Photon Detuning [kHz] ∆m = -1 ∆m = 0 ∆m = +1

∆νHF |1⟩ |2⟩

|3⟩

ω1 ω2

Blaubeuren Summer School July 29, 2013

Atom Interferometer Magnetometer

Blaubeuren Summer School July 29, 2013

• Ramsey (Magnetic)

Atom Interferometer Magnetometer

π/2 π/2

• Spin Echo (Magnetic)

π/2 π/2 π

T2* ~ 55 us T2e ~ 55 us

Blaubeuren Summer School July 29, 2013

• Magnetometry is useful for a broad range of applications from biomagnetics to remote detection

• Atom Interferometry allows NMR like pulse control sequences as a lock-in-amplifier for magnetic signals

• Using these techniques combined with gradiometry, we can detect signals in a magnetically noisy environment

Conclusions

Thank you for your attention!

Questions?

Blaubeuren Summer School July 29, 2013

Other experiments-then

Leonard Mandel 1927-2001

“…could be interesting. But it’s not fundamental

enough”

Photo courtesy J. Mandel

maybe

Bonus Material

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Multiple Pulse Interferometer Sequences

T/2 T/2

π/2 π/2 π

π/2 π/2 π π π

g(ω

) g(

ω)

Frequency [kHz]

Frequency [kHz]

N = 1

N = 3

NMR: Carr Purcell PR 94 630 (1954) Ions: Biercuk Nature 458 996 (2009) Atoms: Davidson PRL 105,053201 (2010) NV Centers: Lukin, Rugar, Cappellaro … Superconductors: Bylander Nature Phys 565 1994 (2011)

Blaubeuren Summer School July 29, 2013

Rabi cycling: m 0 to m 0 transition

universal gates ability to read out

TRaman Readout

TRaman [ms]

π

π/2

5 2S1/2

5 2P3/2

F' = 4

F' = 3

F' = 2 F' = 1

F = 3

F = 2

Time

pulseT1

=∆υ

Two photon detuning νHF/2

R+

R- AOM

Blaubeuren Summer School July 29, 2013

Atom Interferometer

y

π/2 π/2 π

∆νHF |1⟩ |2⟩

|3⟩ |1⟩

|2⟩

ω1 ω2 ω1

ω2

π/2 π/2 π

0 T/2 T t

|1⟩

|2⟩

|1⟩

|2⟩

|1⟩

|2⟩

g

Davis & Narducci, JMO 55 3173 (2008) Zhou et al. PRA 82 061602 (2010)

|1⟩

x

( )

∂−∂−+

−−=∆

∫∫ ttBttBmgmg

gTkkT

T

T

FFFFB

2/

2/

0''

221

)()()(

µ

φ

Blaubeuren Summer School July 29, 2013

Magnetically sensitive Ramsey interferometer

T

π/2 π/2

(Double Delay)

g(ω

)

Frequency [kHz] Two-photon Detuning [kHz]

Dou

ble

Del

ay [u

s]

g(ω,τ ) = sinc2[ωτ /2]

Blaubeuren Summer School July 29, 2013

• Rabi flopping in a magnetically noisy environment:

Atom Interferometer Magnetometer

Blaubeuren Summer School July 29, 2013

Sensitivity

Blaubeuren Summer School July 29, 2013

Filter Functions Time / Frequency Domain

Blaubeuren Summer School July 29, 2013

Keep Sensitivity; Design Around the Noise

Rev. Sci. Instrum. 77, 101101 (2006)

Commercially-available SQUIDS

kHz Hz mHz Frequency

B-F

ield

nT

pT

fT

Shielded Room

Cannot remove magnetic noise in remote sensing

1. Filter out of band noise 2. Measure magnetic field

gradient (Gradients used for object location)

Blaubeuren Summer School July 29, 2013

Homecoming

Lorenzo Narducci 1942-2006

Leonard Mandel 1927-2001

Photo courtesy J. Mandel

Blaubeuren Summer School July 29, 2013

17 years later

Blaubeuren Summer School July 29, 2013

Other experiments-then

Leonard Mandel 1927-2001

“…could be interesting. But it’s not fundamental

enough”

Photo courtesy J. Mandel

Blaubeuren Summer School July 29, 2013

Definition of π pulse

π

Blaubeuren Summer School July 29, 2013

Definition of π/2 pulse

π/2