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The coolest places in the universe

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Title: The coolest places in the universe


1
The coolest places in the universe
Paul C. Haljan University of Michigan Oct. 2003
2
I. Laser cooling atoms
Magnets
Lasers
3
II. Quantum Tornadoes Near Absolute Zero
Courtesy NOAA
4
Cd
Cadmium quantum bits
5
The world circa 1920s
6
Fifth Solvay Conference 1927Electrons and
photons
Quantum Theory Quantum Wave Mechanics - takes
flight
7
Everyday waves Sound waves
Source
Detector
Pressure
Wavelength 30cm at 1000Hz frequency
time
8
  • Waves can add (constructive interference)


Louder
or cancel (destructive interference)

Silent
9
Interference you can hear it!
10
You can see interference too.
Light interference Youngs double slit experiment
Laser
Wavelength l
Light intensity
Electromagnetic waves
11
How about a double slit experiment for particles
(atoms)?
Particle Detector
Beam of particles
12
How about a double slit experiment for particles
(atoms)?
Particle Detector
Beam of particles
Distribution is built up from single particle
detections
13
How about a double slit experiment for particles
(atoms)?
Sorry!
Beam of particles
14
How about a double slit experiment for particles
(atoms)?
Beam of particles
Intensity(both slits) I1I2
15
Double slit experiment for particles
  • Interference!!!!

electrons
atoms
Hitachi
Carnal, Mlynek 1991
16
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
17
So whats interfering?
  • de Broglie wavelength
  • h Plancks constant (tiny)
  • m mass
  • v particle velocity

Louis deBroglie
McEvoy Zarate
18
Schrödingers Equation for quantum wave mechanics
Y wavefunction
Y(x,t)2 probability of finding particle at
position x at time t.
McEvoy Zarate
19
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
20
Cold - the quantum frontier!
Gas
de Broglie wavelength
Temperature (random jiggling)
Thermal velocity
de Broglie wavelength
hot fast cold slow
BIG!
21
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
22
Lasers zap, burn, cut
How do they COOL atoms????
23
Rb
A
Laser
Pushing atoms with light
Acceleration 100 000 gs!!!!
24
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!!!!
25
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!
26
Laser molasses
APPLET
27
I. Laser cooling atoms
Lasers
28
BEC intro II
JILA Mark III
29
JILA Mark III
1 billion atoms 10-100uK
30
Atom Interferometry (AI)
31
Light interferometers
Wave interference can be used to measure
(changes in) path length difference
mirror
mirror
Beam splitter
Detector
32
LIGO pict
A really BIG light interferometer!
4km
LIGO Gravitational wave detector Hanford WA
33
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!
34
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)
35
Gravimetry
Gravitational force
mass
(distance)2
MASSIVE BLOB
36
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

37
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)
38
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
39
II. Quantum Tornadoes Near Absolute Zero
Plus .what kind of thermometer measures the
coldest places in the universe anyways?
Courtesy NOAA
40
(No Transcript)
41
How to make a thermometer for cold atoms
Images of clouds
Let the gas expand
Hot cloud
Cold cloud
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