Title: The coolest places in the universe
1The 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
4Cd
Cadmium quantum bits
5The world circa 1920s
6Fifth Solvay Conference 1927Electrons and
photons
Quantum Theory Quantum Wave Mechanics - takes
flight
7Everyday waves Sound waves
Source
Detector
Pressure
Wavelength 30cm at 1000Hz frequency
time
8- Waves can add (constructive interference)
Louder
or cancel (destructive interference)
Silent
9Interference you can hear it!
10You can see interference too.
Light interference Youngs double slit experiment
Laser
Wavelength l
Light intensity
Electromagnetic waves
11How about a double slit experiment for particles
(atoms)?
Particle Detector
Beam of particles
12How about a double slit experiment for particles
(atoms)?
Particle Detector
Beam of particles
Distribution is built up from single particle
detections
13How about a double slit experiment for particles
(atoms)?
Sorry!
Beam of particles
14How about a double slit experiment for particles
(atoms)?
Beam of particles
Intensity(both slits) I1I2
15Double slit experiment for particles
electrons
atoms
Hitachi
Carnal, Mlynek 1991
16If 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
17So whats interfering?
- de Broglie wavelength
- h Plancks constant (tiny)
- m mass
- v particle velocity
Louis deBroglie
McEvoy Zarate
18Schrödingers Equation for quantum wave mechanics
Y wavefunction
Y(x,t)2 probability of finding particle at
position x at time t.
McEvoy Zarate
19Particle 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
20Cold - the quantum frontier!
Gas
de Broglie wavelength
Temperature (random jiggling)
Thermal velocity
de Broglie wavelength
hot fast cold slow
BIG!
21How 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
22Lasers zap, burn, cut
How do they COOL atoms????
23Rb
A
Laser
Pushing atoms with light
Acceleration 100 000 gs!!!!
24Its 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!!!!
25Problem 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!
26Laser molasses
APPLET
27 I. Laser cooling atoms
Lasers
28BEC intro II
JILA Mark III
29JILA Mark III
1 billion atoms 10-100uK
30Atom Interferometry (AI)
31Light interferometers
Wave interference can be used to measure
(changes in) path length difference
mirror
mirror
Beam splitter
Detector
32LIGO pict
A really BIG light interferometer!
4km
LIGO Gravitational wave detector Hanford WA
33de 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!
34Atom 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)
35Gravimetry
Gravitational force
mass
(distance)2
MASSIVE BLOB
36Example 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
37Laboratory 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)
38Applications
- 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)
41How to make a thermometer for cold atoms
Images of clouds
Let the gas expand
Hot cloud
Cold cloud