Quantum wierdness at the lowest temperatures in the Universe

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Bose-Einstein condensation Quantum weirdness at
the lowest temperature in the universe
Part I. Introduction to quantum physics Part
II. (1924-95) Making Bose-Einstein Condensation
in a gas. BEC- a new form of matter predicted
by Einstein in 1924 and first created in 1995 by
our group. Part III. An example of research
with BEC.
Spread clickers throughout the room, no two
clickers next to each other. PRESS ON/OFF
BUTTON ON CLICKER. Light appears
(NSF, ONR, NIST)
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clicker data gathering
CQ1. Age? A. less than 10 years old B.
10-14 C. 15-18 D. 18-23
E. 23- 99 yrs old
CQ2. Most advanced physics classes taken? a. none
b. physics 11 or 12 c. a college or
university physics class d. college or university
quantum physics class e. graduate school physics
class
anyone who answered e. (graduate school physics)
, give clicker to someone not in category e.
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Bose-Einstein condensation Quantum weirdness at
the lowest temperature in the universe
Part I. Basics of quantum physics A. Location
of particle as probability wave B. Particles
only allowed to have particular energies C.
Energies of electrons in atoms
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A. Location of particle as probability wave
Shoot electron at screen-- see where it is
detected.
Repeat with new electron, everything else as
exactly the same as possible. CQ3. Where on
the screen will it be detected? (discuss with
neighbors, then vote)
a. anywhere on screen. b. anywhere except
where first one hit. c. at same spot as
where first one hit d. in center of the
screen e. some other answer
ans. a anywhere on screen
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Send electron through double slit. CQ5. Where
will it be detected on the screen? (super
submicroscopic machine!!) a. just like before,
anywhere in broad region. b. anywhere in two
broad regions-- one on each side with gap in
middle. c. somewhere in one of a few bands, but
not in spaces between those bands d. will not be
screen at all, because is too wide to get through
slits.
send some electrons
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CQ5. Send electron through double slit. Where
will it be detected on the screen? a. just like
before, anywhere in broad region. b. anywhere in
two broad regions-- one on each side with gap in
middle. c. somewhere in one of a few bands, but
not in spaces between those bands d. will not be
screen at all, because is too wide to get through
slits.
wave interference sim
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Electrons interfere like waves! Where waves
add, lots of electrons detected, waves cancel-
none.
waves cancel
wave interference sim
waves add- bigger wave
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atoms same as electrons-- just slower time
scale smaller spacing between waves.
CQ6. Why not see normal objects with location
fuzzy-- described by probability wave,
interference etc.? a. they are moving around
too fast so dont see fuzziness. b. are spread
out, but over too small a distance to see. c.
this whole explanation is crazy and wrong. d.
because fuzziness only can be seen if objects are
very hot.
ans. b They are spread out, but over very small
distance.
How small depends on weight and temperature of
object. room temp electron spread (fuzzed) out
over 0.000 000 007 m atom is
spread over 0.000 000 000 02 m hockey puck--
spread over 0.000 000 000 000 000 000
000 02 m
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First important idea of quantum physics Location
of object described by probability wave. When
detect, see it at one spot, but identical object
will be detected in different place-- just
probability.
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B. Particles only allowed to have particular
energies
Where particle can be found is described by
probability wave What does that mean when
particles (electrons, atoms) in a container?
Waves have to just fit. Potential well sim.
2nd lowest energy
lowest energy particle
What will wave look like for next level?
higher energy waves have more wiggles
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2nd Important Idea of Quantum Physics Particles
in container can only have certain energies --
correspond to where wave just fits into
container. Cannot exist with other energies!
?gap between energies Energy is quantized ?
quantum physics
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What does the gap between energy levels depend
on? CQ7. What happens to energy gap if make
container wider? a. gets larger (allowed
energies get farther apart). b. stays the
same. c. gets smaller (allowed energies get
closer together)
check with sim
ans. c. levels get closer together
CQ8. Why if we look at cars, people, MMs in jar,
etc., they appear to have any energy/speed they
want (no gaps)? a. quantum physics only applies
to electrons b. quantum physics applies to things
that are too small to see, like electrons or
atoms, but not to normal sized objects. c. for
human size scale objects, energy levels are
there, but too close together to see gaps. d.
hockey pucks, people, etc are jumping around
between different energy levels so fast, we cant
see or measure the gaps.
ans. c.
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C. Energies of electrons in atoms
Electron held in an atom is in very small
container. ? Bigger energy gaps. Slightly
different for each atom. Can only absorb exact
amount of energy needed to jump to higher level
(color of light) Can only give off exact amount
of energy (light of particular color) needed to
jump to lower level.
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Key ideas of quantum physics 1. Location of
particle fuzzy-- defined by probability wave. 2.
Particle can only have certain energies in
container, higher energy more wiggles in
probability wave. (? wiggles farther apart when
energy lower ) 3. Electron stuck in atom-- can
only have certain energy levels. Will only jump
up to higher energy if exactly right color
light (right energy) hits it. Jumps back down and
gives off exactly energy difference (particular
color light)
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Part II. (1924-95) Making Bose-Einstein
Condensation in a gas. BEC- a new form of
matter predicted by Einstein in 1924 and first
created in 1995 by our group.
JILA BEC Effort Eric Cornell, Carl Wieman
1990- Anderson, Ensher, Jin, Hall, Matthews,
Myatt, Monroe, Claussen, Roberts, Cornish,
Haljan, Donley, Thompson, Papp, Zirbel,
Lewandowski, Harber, Coddington, Engels, McGuirk,
Hodby,...
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temperature applet
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Absolute (Kelvin)
CQ8. Where is the coldest place in the
universe. a. Boulder Colorado b. Antarctica c.
recently demoted planet Pluto d. halfway between
sun and next closest star e. intergalactic space
(between galaxies)
300
earth
250
200
150
100
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Absolute zero! All motion stops -273 oC
0
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Absolute (Kelvin)
Room Temp
300
earth
Water freezes
250
Dry Ice
200
150
100
Air freezes
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Deep space, 3 K
Absolute zero! All motion stops -273 oC
0
BEC at .000 000 1o above Absolute zero
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Boulder Colorado
CSIU
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Cold atoms
Hot atoms (more than 10 millionths of degree
above abs. zero)
A. E. 1924
colder lower energy
?? spacing between prob. wave wiggles? a.
smaller b. larger
energy levels too close together to detect
BEC
100 billionths of a degree
1 cm bowl
"superatom" --single quantum wave
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evacuated glass cell
coils of wire
B coils
diode lasers (cheap)
2.5 cm
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JILA BEC 2 (1 at Smithsonian)
2 in.
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Grad students Neil Claussen, Sarah Thompson,
postdoc Liz Donley working on BEC experiment.
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Getting atoms cold- step 1
Rb
A
Laser
Pushing atoms with light
Why does sunlight heat you up, but laser light
cools these atoms down?
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gas atoms can absorb and reradiate light a. that
is whatever the color of light that shines on
them b. that is bluer (higher energy) light than
the first energy gap c. that is at only at
particular precise frequencies or colors.
ans. c.
if light just the right color electrons absorb
light jump to higher energy level jump back down,
give off light
laser cooling applet
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optical molasses applet magnetic trapping
applet evaporative cooling applet
www.colorado.edu/physics/2000/ BEC section
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Shadow snapshot of BEC
CCD array (TV camera)
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Shadow images of clouds
1
2

• CQ. Which cloud is hotter?
• 1 is hotter than 2.
• 2 is hotter than 1.
• Impossible to tell just from shadow picture

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Shadow images of clouds
Hot cloud
Cold cloud
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BEC! JILA-June 1995
50 billionths
200 billionths
400 billionths of degree
0.2 mm
False color images of cloud
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Cold atoms
Hot atoms (microKelvins)
A. E. 1924
Bosons
lowest level smallest width- set by uncertainty
principle
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Quantum physics on human size scale Control
and Observe
Putting one condensate on top of another

about width of human hair
Fringes formed with two overlapping condensates-
probability waves interfering!
(NIST Gaithersburg atom cooling group -
courtesy S. Rolston)
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Where BEC now (post June 95)?
New regime of physics- directly observe and
manipulate quantum wave function 250
working experiments, many atoms (87Rb, Na, Li,
H, 85Rb, He,K, Cs) countless
theorists- many thousands of papers

gt1000 scientists

• Measured and predicted all sorts of novel
  properties.
• New ways to study, make and manipulate.
• Potential applications.

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Stockholm Sweden, Dec. 10, 2001
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Part III. Some research with BEC New
material. Explore behavior, find occasional
surprises, understand ? new understanding of
nature.
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Controlling self-interactions with 85Rubidium BEC
Roberts, Claussen, Donley, Thompson, CEW
attractive (Li, 85Rb), a lt 0 (unstable if N
large, Nmax?1/a)
repulsive (87RB, Na), a gt 0
in 85 Rb have experimental knob to adjust from
large repulsive to nothing to large attractive!

3 billionths of a degree!
Magnetic field
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Plunging into the unknown interaction attractive
Lots of theory, varied wildly. Little data
?
2. Switch to attractive.

• Make BEC
• magnetic field
• where repulsive

What happens? (how do quantum wavefunctions die?)
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Collapse
time
then
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Explosion !!
x 3
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10,000 atoms

• like supernova
• collapse
• explosion (x 10-73 )
• cold remnant

0.2ms
0.7ms
Bosenova
1.8ms
0.1 mm
What is the physics of explosion??? Why remnant
remains?
2.3ms
progress
4.3ms
1500 atom explosion T 200 nK
4.8ms
X 3
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source of energy of Bosenova--chemical
A New Type of Chemistry--

• changing magnetic field just right turns atoms in
  BEC into unusual Rb2 "molecules".
• 10,000 times larger than normal molecules
• new formation processes

learned something new about nature--being studied
and used for all sorts of research.
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Quantum physics interactive simulations (and
many many more for learning lots of other
physics) at PHET.Colorado.edu Laser cooling,
magnetic trapping and evaporative cooling
simulations (and more) www.colorado.edu/physics/
2000/ see BEC section
end
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(what is it good for?)
What is next ?
I. Measure and understand properties. New
area of quantum world to explore turning BEC
atoms into strange new sort of molecules
II. Uses (??).... 5-20 years (laser-like
atoms) a. Ultrasensitive detectors (time,
gravity, rotation). making a quantum
computer(?). b. Making tiny
stuff--putting atoms exactly where want them

simulations shown (and more) www.colorado.edu/phy
sics/2000/ see BEC section interactive
simulations for quantum and lots of other physics
PHET.Colorado.edu