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.

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.

$$ (NSF, ONR, NIST)

Bose-Einstein Bose-Einstein condensation; Quantum condensation; Quantum weirdness at the lowest weirdness at the lowest temperature in the universetemperature in the universe

Spread clickers throughout the room, no two clickers next to eachother. PRESS “ON/OFF” BUTTON ON CLICKER. Light appears

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 classd. college or university quantum physics classe. graduate school physics class

anyone who answered e. (graduate school physics) ,give clicker to someone not in category e.

clicker data gathering

Part I. Basics of quantum physicsA. Location of particle as probability waveB. Particles only allowed to have particular energiesC. Energies of electrons in atoms

Bose-Einstein Bose-Einstein condensation; Quantum condensation; Quantum weirdness at the lowest weirdness at the lowest temperature in the universetemperature in the universe

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 screene. some other answer

ans. a anywhere on screen

A. Location of particle as probability wave

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 bandsd. will not be screen at all, because is too wide to get through slits.send some electrons

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 bandsd. will not be screen at all, because is too wide to get through slits.

wave interference sim

wave interference sim

Electrons interfere like waves! Where waves add, lots of electrons detected, waves cancel- none.

waves cancel

waves add- bigger wave

atoms same as electrons-- just slower time scalesmaller spacing between waves.

CQ6. Why not see normal objects with location fuzzy-- describedby probability wave, interference etc.?

a. they are moving around too fast so don’t 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 tempelectron spread (fuzzed) out over 0.000 000 007 m atom is spread over 0.000 000 000 02 mhockey puck-- spread over 0.000 000 000 000 000 000 000 02 m

First important idea of quantum physics

Location of object described by probability wave.

When detect, see it at one spot, but identical object willbe detected in different place-- just probability.

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.

What will wave look like for next level?

higher energy waves have more wiggles

lowest energy particle2nd lowest energy

B. Particles only allowed to have particular energies

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”

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, M&Ms in jar, etc., they appear to have any energy/speed they want (no gaps)?

a. quantum physics only applies to electronsb. 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 can’t see or measure the gaps. ans. c.

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 jumpto higher level (color of light)

Can only give off exact amount of energy (light of particular color)needed to jump to lower level.

C. Energies of electrons in atoms

Key ideas of quantum physics1. 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)

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,...

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.

temperature applet

Absolute(Kelvin)

Absolute zero!All motion stops-273 oC

250

200

150

100

50

0

earth300

CQ8. Where is the coldest place in the universe.a. Boulder Coloradob. Antarcticac. recently demoted planet Plutod. halfway between sun and nextclosest stare. intergalactic space (between galaxies)

Absolute(Kelvin)

Room Temp

Water freezes

Dry Ice

Air freezes

Deep space, 3 K

BEC at .000 000 1o above Absolute zero

Absolute zero!All motion stops-273 oC

250

200

150

100

50

0

earth300

CSIU

Boulder Colorado

Hot atoms(more than 10 millionthsof degree above abs. zero)

Cold atomsA. E. 1924

BEC

100 billionths of a degree

"superatom" --single quantum wave

energy levels too closetogether to detect

1 cm bowl

colder = lower energy

= ?? spacing between prob.wave wiggles?a. smallerb. larger

evacuatedglass cell

diode lasers(cheap)

B coils

2.5 cm

coils of wire

JILA BEC #2 (#1 at Smithsonian)

2 in.

Grad students Neil Claussen, Sarah Thompson, postdoc Liz Donleyworking on BEC experiment.

Pushing atoms with light

Rb

Getting atoms cold- step 1

Why does sunlight heat you up, but laser light cools these atoms down?

gas atoms can absorb and reradiate light a. that is whatever the color of light that shines on themb. that is bluer (higher energy) light than the first energy gapc. 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 leveljump back down, give off light

laser cooling applet

optical molasses appletmagnetic trapping appletevaporative cooling applet

www.colorado.edu/physics/2000/ BEC section

Shadow “snapshot” of BEC

CCD array(TV camera)

Shadow images of clouds

1 2

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

Hot cloud Cold cloud

Shadow images of clouds

False color images of cloud

400 billionthsof degree

~ 200 billionths

50 billionths

0.2 mm

BEC! JILA-June 1995

Hot atoms(microKelvins)

Cold atomsA. E. 1924

Bosons

lowest level smallestwidth- set by uncertainty principle

Quantum physics on “human” size scale Control and Observe

Fringes formed with two overlapping condensates- probability waves interfering!

about width of human hair

Putting one condensate on top of another

(NIST Gaithersburg atom cooling group - courtesy S. Rolston)

•Measured and predicted all sorts of novel properties.

•New ways to study, make and manipulate.

•Potential applications.

Where BEC now (post June ‘95)?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

>1000 scientists

Stockholm Sweden, Dec. 10, 2001

Part III. Some research with BEC

New material. Explore behavior, find occasional surprises,

understand new understanding of nature.

repulsive (87RB, Na), a > 0 attractive (Li, 85Rb), a < 0 (unstable if N large, Nmax1/a)

Controlling self-interactions with 85Rubidium BEC

in 85 Rb have experimental knob to adjust from large repulsive to nothing to large attractive!

Magnetic field

Roberts, Claussen, Donley, Thompson, CEW

3 billionths of a degree!

Plunging into the unknown– interaction attractive Plunging into the unknown– interaction attractive

Lots of theory, varied wildly.Little data

1. Make BEC magnetic field where repulsive

2. Switch to attractive.

?

What happens?(how do quantum wavefunctions die?)

CollapseStart: 10,000 atom BEC

then…

time

Explosion !!x 3

0.2ms

0.7ms

1.8ms

4.3ms

4.8ms

2.3ms

1500 atom explosionT ~ 200 nK

What is the physics of explosion???Why remnant remains?

0.1 mm

X 3

10,000 atomslike supernova:•collapse•explosion… (x 10-73 )•cold remnant

“Bosenova”

progress…

A New Type of Chemistry-- 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

source of energy of Bosenova--chemical

learned something new about nature--being studied and used for all sorts of research.

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

(what is it good for?)

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/physics/2000/ see BEC section

interactive simulations for quantum and lots of other physics PHET.Colorado.edu