frequency tunable atomic magnetometer based on an atom ... · d.a. braje1, j.p. davis2, c.l....
Post on 04-Aug-2020
2 Views
Preview:
TRANSCRIPT
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
Blaubeuren Summer School July 29, 2013
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)
Blaubeuren Summer School July 29, 2013
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!
Blaubeuren Summer School July 29, 2013
• 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!
Blaubeuren Summer School July 29, 2013
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
Blaubeuren Summer School July 29, 2013
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
Blaubeuren Summer School July 29, 2013
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
top related