BoseEinstein condensation Quantum weirdness at the lowest temperature

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)

clicker data gathering CQ 1. Age? A. less than 10 years old C. 15 -18 D. 18 -23 B. 10 -14 E. 23 - 99 yrs old CQ 2. 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.

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

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. CQ 3. 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

Send electron through double slit. CQ 5. 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

CQ 5. 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

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

atoms same as electrons-- just slower time scale smaller spacing between waves. CQ 6. Why not see normal objects with location fuzzy-- described by 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 temp electron spread (fuzzed) out over 0. 000 007 m atom is spread over 0. 000 000 02 m hockey puck-- spread over 0. 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 will be detected in different place-- just probability.

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. 2 nd lowest energy particle What will wave look like for next level? higher energy waves have more wiggles

2 nd 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? CQ 7. 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 CQ 8. 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 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 can’t see or measure the gaps. ans. c.

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.

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)

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, Mc. Guirk, Hodby, . . .

temperature applet

Absolute (Kelvin) earth 300 250 200 150 100 50 Absolute zero! 0 All motion stops -273 o. C CQ 8. 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)

Absolute (Kelvin) earth 300 250 200 Room Temp Water freezes Dry Ice 150 100 Air freezes 50 Absolute zero! 0 All motion stops -273 o. C Deep space, 3 K BEC at. 000 1 o above Absolute zero

Boulder Colorado CSIU

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 1 cm bowl 100 billionths of a degree "superatom" --single quantum wave

evacuated glass cell coils of wire diode lasers (cheap) B coils 2. 5 cm

JILA BEC #2 (#1 at Smithsonian) 2 in.

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

Getting atoms cold- step 1 Rb Pushing atoms with light 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 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

optical molasses applet magnetic trapping applet evaporative 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

Shadow images of clouds Hot cloud Cold cloud

BEC! JILA-June 1995 50 billionths 400 billionths of degree ~ 200 billionths 0. 2 mm False color images of cloud

Cold atoms Hot atoms (micro. Kelvins) A. E. 1924 Bosons lowest level smallest width- set by uncertainty principle

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) -

Where BEC now (post June ‘ 95)? New regime of physicsdirectly observe and manipulate quantum wave function ~ 250+ working experiments, many atoms (87 Rb, Na, Li, H, 85 Rb, He*, K, Cs) >1000 scientists countless theoristsmany thousands of papers • Measured and predicted all sorts of novel properties. • New ways to study, make and manipulate. • Potential applications.

Stockholm Sweden, Dec. 10, 2001

Part III. Some research with BEC New material. Explore behavior, find occasional surprises, understand new understanding of nature.

Controlling self-interactions with 85 Rubidium BEC Roberts, Claussen, Donley, Thompson, CEW repulsive (87 RB, Na), a > 0 attractive (Li, 85 Rb), a < 0 (unstable if N large, Nmax 1/a) in 85 Rb have experimental knob to adjust from large repulsive to nothing to large attractive! Magnetic field 3 billionths of a degree!

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? )

Start: 10, 000 atom BEC Collapse time then…

x 3 Explosion !!

10, 000 atoms like supernova: • collapse • explosion… (x 10 -73 ) • cold remnant 0. 2 ms 0. 7 ms “Bosenova” 0. 1 mm 1. 8 ms 2. 3 ms What is the physics of explosion? ? ? Why remnant remains? progress… 4. 3 ms 1500 atom explosion T ~ 200 n. K 4. 8 ms X 3

source of energy of Bosenova--chemical A New Type of Chemistry-changing magnetic field just right turns atoms in BEC into unusual Rb 2 "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.

Quantum physics interactive simulations (and 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/ section end see BEC

(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