The coolest places in the universe

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The coolest places in the universe
Paul C. Haljan University of Michigan Oct. 2003
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I. Laser cooling atoms
Magnets
Lasers
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II. Quantum Tornadoes Near Absolute Zero
Courtesy NOAA
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Cd
Cadmium quantum bits
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The world circa 1920s
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Fifth Solvay Conference 1927Electrons and
photons
Quantum Theory Quantum Wave Mechanics - takes
flight
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Everyday waves Sound waves
Source
Detector
Pressure
Wavelength 30cm at 1000Hz frequency
time
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• Waves can add (constructive interference)

Louder
or cancel (destructive interference)

Silent
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Interference you can hear it!
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You can see interference too.
Light interference Youngs double slit experiment
Laser
Wavelength l
Light intensity
Electromagnetic waves
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How about a double slit experiment for particles
(atoms)?
Particle Detector
Beam of particles
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How about a double slit experiment for particles
(atoms)?
Particle Detector
Beam of particles
Distribution is built up from single particle
detections
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How about a double slit experiment for particles
(atoms)?
Sorry!
Beam of particles
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How about a double slit experiment for particles
(atoms)?
Beam of particles
Intensity(both slits) I1I2
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Double slit experiment for particles

• Interference!!!!

electrons
atoms
Hitachi
Carnal, Mlynek 1991
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If only one particle at a time passes through
the interferometer .. an interference pattern
still builds up!!!!
click
Intensity pattern shows up After many particles
detected
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So whats interfering?

• de Broglie wavelength
• h Plancks constant (tiny)
• m mass
• v particle velocity

Louis deBroglie
McEvoy Zarate
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Schrödingers Equation for quantum wave mechanics
Y wavefunction
Y(x,t)2 probability of finding particle at
position x at time t.
McEvoy Zarate
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Particle interferometry with ever bigger, more
complex objects!
de Broglie wavelength
Mass / proton mass

• (Photons) 0
• Electrons 1950s 0.0005
• Neutrons 1975 1
• Atoms 1991 10-100
• Buckyballs and biomolecules 2003 gt1000

C44H30N4
C60F48
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Cold - the quantum frontier!
Gas
de Broglie wavelength
Temperature (random jiggling)
Thermal velocity
de Broglie wavelength
hot fast cold slow
BIG!
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How cold is cold?
Temperature
300 81
Florida
Rubidium atom
Thermal velocity
de Broglie wvlen. (microns)
Temp.
Michigan winter
300 K 300m/s 1x10-5 300 mK
30cm/s 0.01 300 nK 1cm/s 1
200 -99
Record low (Antartica)
virus
Absolute (Kelvin)
Fahrenheit (degrees)
E-coli
100 -269
Air liquifies
1nK0.000 000 001 K
Triton
Outer space (3K)
0 -460
Absolute zero all motion stops
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Lasers zap, burn, cut
How do they COOL atoms????
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Rb
A
Laser
Pushing atoms with light
Acceleration 100 000 gs!!!!
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Its a bit harder than that .. An atom only
absorbs specific colors. (explained by quantum
theory).
The laser for Rubidium atoms is a deep red.
Lowest A
Atom is really specific!!! A single key on a 26
million key piano!!!!
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Problem How can we stop the fast atoms without
speeding up the slow ones in a gas?
Atom moving towards the laser scatters photons
Laser
Stopped atom doesnt scatter
Solution Doppler effect The color the atom
absorbs depends on its velocity!
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Laser molasses
APPLET
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I. Laser cooling atoms
Lasers
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BEC intro II
JILA Mark III
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JILA Mark III
1 billion atoms 10-100uK
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Atom Interferometry (AI)
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Light interferometers
Wave interference can be used to measure
(changes in) path length difference
mirror
mirror
Beam splitter
Detector
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LIGO pict
A really BIG light interferometer!
4km
LIGO Gravitational wave detector Hanford WA
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de Broglie Wave Interference
Particle wavepacket
Neutron interference MICHIGAN 1975
Atoms (v1m/s) Compare with light waves

• h/mv
• de Broglie wavelength

Shorter wavelength a more sensitive ruler!
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Atom Interferometer Force Sensors
The quantum mechanical wave-like properties of
atoms are used to sense inertial forces.
Gravity/Accelerations
As atom climbs gravitational potential, velocity
decreases and wavelength increases
LONGER de Broglie wavelength
gravity
SHORTER de Broglie wavelength
(Rotations also sensed)
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Gravimetry
Gravitational force
mass
(distance)2
MASSIVE BLOB
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Example Light-Pulse AI Gravity Gradiometer
G. McGuirk, M. Kasevich

• Gradient measurements Distinguish gravity
  induced accelerations from those due to platform
  motion.
• Simultaneously measure g at two locations with
  atom interferometer accelerometers
• Difference acceleration signal contains gradient
  information

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Laboratory validation Mass Detection
G. McGuirk, M. Kasevich
Modulated acceleration signal due to 8 lead
bricks near lower accelerometer.
Pb bricks
Gradient (arb. units)
Lower accelerometer
Successful laboratory demonstration of mass
anomaly detection capabilities
Sample number (1 sample/sec)
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Applications

• SSN/SSBN Navigation - Gravity assisted navigation
  (currently in use on subs, but need better)
• Underground structure detection (a.k.a. bunker
  detection)
• Oil and mineral exploration (e.g. kimberlite
  pipes in Utah diamonds come from kimberlite, or
  salt domes in the Gulf of Mexico oil)
• Space-based studies of Earths gravity field

LM UGM
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II. Quantum Tornadoes Near Absolute Zero
Plus .what kind of thermometer measures the
coldest places in the universe anyways?
Courtesy NOAA
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(No Transcript)
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How to make a thermometer for cold atoms
Images of clouds
Let the gas expand
Hot cloud
Cold cloud