precision navigation sensors based on atom interferometry...kasevich_presentation.pptx author: tom...
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Precision Navigation Sensors based on Atom Interferometry
Mark Kasevich Depts. of Physics and Applied Physics Stanford University
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Young’s double slit interferometer with atoms
Mlynek, PRL, 1991
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Young’s double slit interference fringes
Mlynek, PRL, 1991
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1991 Light-Pulse Atom Interferometer
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Light-pulse atom interferometry
Pulses of light are used to coherently manipulate atom de Broglie waves:
Kasevich and Chu, PRL, 1991
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Images of atoms in interferometer
Chiow, PRL, 2011
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1.4 cm wavepacket separation (!)
Interference contrast observed for 1.4 cm wavepacket separation.
Est. δg < 1e-11 g/shot accelerometer sensitivity.
10 m atomic fountain apparatus
Interference
Control
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Simple model for acceleration sensitivity
g
As atom climbs gravitational potential, velocity decreases and de Broglie wavelength increases ….
Phase shift determines probability of detecting atom in a given output port.
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Simple model for rotation sensitivity
Sagnac effect for de Broglie waves ….
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Gyroscope (1997)
Gustavson, PRL, 1997
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Gyroscope interference fringes
Noise: 3 µdeg/hr1/2
Bias stability: < 60 µdeg/hr
Scale factor: < 5 ppm Gustavson, PRL, 1997 Durfee, PRL, 2006
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Light-pulse AI Gyroscope Performance
AI
Source: Proc. IEEE/Workshop on Autonomous Underwater Vehicles
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Light-pulse AI Accelerometer Performance
AI
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Why superb sensors?
• Atom = near perfect inertial reference.
• Laser/atom interactions register relative motion between atom and sensor case.
• Sensor accuracy derives from the exceptional stability of optical wavefronts.
• Direct read-out of angular and linear displacements.
Sensor Case
Atoms
Accelerometer
Sensor Case
Atoms
Gyroscope
v
Laser
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Hybrid sensor/Gyroscope mode
Measured gyroscope output vs.orientation:
Typical interference fringe record:
• Inferred ARW: < 100 µdeg/hr1/2
• 10 deg/s max input • <100 ppm absolute accuracy
Stockton, PRL, 2011
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Interior view of sensor
Hybrid sensor operation
Interior view
Interference fringes are recorded by measuring number of atoms in each quantum state.
Fringes are scanned electro-optically.
F=3
F=4
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Hybrid sensor/Gravity gradient mode
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Hybrid sensor/Absolute accelerometer
Horizontal input axis, microGal resolution.
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Gravimeter, Measurement of g
Fabricated and tested at AOSense, Inc., Sunnyvale, CA.
Sensors designed for precision navigation.
AOSense, Inc. DARPA DSO
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Gyroscope/Rotational Seismology
AOSense, Inc. DARPA DSO
+30 min
Gyroscope output necessary to disambiguate tilt from horizontal motion (navigation problem).
Honduras/offshore 7.3
ANGLE
VELOCITY
CMG3
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The challenge…
? how
408-735-9500 AOSense.com Sunnyvale, CA
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Compact Zeeman slower
408-735-9500 AOSense.com Sunnyvale, CA
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AOSense Commercial Compact Gravimeter
Commercial Cold Atom Gravimeter • Noise < 1 µg/Hz1/2
• Shipped 11/22/10 • First commercial
atom optics sensor
408-735-9500 AOSense.com Sunnyvale, CA
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(Optical) Atomic Clock
408-735-9500 AOSense.com Sunnyvale, CA
6 L physics package. Includes all sub-systems except electronics.
Zeeman slower Sr clock laser Sr oven, 3 W
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System implementation
408-735-9500 AOSense.com Sunnyvale, CA
Space/time vector tracking with integrated atom inertial and clock (courtesy J. Spilker)
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Technology Vision
• Inertial+ grade IMU < 10 liters < 10 m/hr drift < 100 Watts Gravity compensated
• Navigation grade IMU < 0.1 liters < 1 Watt Low-cost ($1K ?)
408-735-9500 AOSense.com Sunnyvale, CA