Paul C. Haljan University of Michigan Oct. 2003

I. Laser cooling atoms Magnets Lasers

II. Quantum Tornadoes Near Absolute Zero Courtesy NOAA

Cd + Cadmium quantum bits

The world circa 1920’s Air = molecules moving around! Atomic constituents Light and radio waves …..

Fifth Solvay Conference 1927 “Electrons and photons” Quantum Theory – “Quantum Wave Mechanics” - takes flight

Everyday waves: Sound waves Source Detector time Pressure Wavelength ~ 30cm at 1000Hz frequency

Waves can add (constructive interference) or cancel (destructive interference) = = Louder Silent

Interference – you can hear it!

You can see interference too. Laser Light intensity Light interference: Young’s double slit experiment Wavelength Electromagnetic waves

How about a double slit experiment for particles (atoms)? Beam of particles Particle Detector

How about a double slit experiment for particles (atoms)? Beam of particles Particle Detector Distribution is built up from single particle detections

How about a double slit experiment for particles (atoms)? Beam of particles Sorry!

How about a double slit experiment for particles (atoms)? Beam of particles Intensity(both slits) =I 1 +I 2

Double slit experiment for particles Interference!!!! electronsatoms Hitachi Carnal, Mlynek 1991

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

So what’s interfering? Louis deBroglie = de Broglie wavelength h = Planck’s constant (tiny) m = mass v = particle velocity McEvoy & Zarate  h mv

Schrödinger’s Equation for quantum wave mechanics McEvoy & Zarate  wavefunction  x,t  2 probability of finding particle at position x at time t.

Particle interferometry with ever bigger, more complex objects! (Photons)0 Electrons – 1950’s Neutrons Atoms Buckyballs and biomolecules 2003>1000 C 44 H 30 N 4 C 60 F 48  h mv Mass / proton mass de Broglie wavelength

Cold - the quantum frontier!  h mv de Broglie wavelength Temperature (random jiggling) Thermal velocity de Broglie wavelength hot fast cold slow Gas BIG!

How cold is cold? Thermal velocity de Broglie wvlen. (microns) Temperature Florida Air liquifies Triton Absolute zero – all motion stops Record low (Antartica) Michigan winter Outer space (3K) Absolute (Kelvin) Fahrenheit (degrees) Temp. 300 K 300m/s1x  K 30cm/s nK 1cm/s 1 1nK= K Rubidium atom virus E-coli

Lasers zap, burn, cut How do they COOL atoms????

Pushing atoms with light Rb Acceleration g’s!!!!

It’s 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!!!!

Problem: How can we stop the fast atoms without speeding up the slow ones in a gas? Solution: Doppler effect “The color the atom absorbs depends on its velocity!” Atom moving towards the laser scatters photons Stopped atom doesn’t scatter

Laser molasses APPLET

I. Laser cooling atoms Lasers

BEC intro II JILA Mark III

~1 billion atoms uK

Atom Interferometry (AI):

Light interferometers Wave interference can be used to measure (changes in) path length difference: mirror Beam splitter Detector

LIGO pict LIGO Gravitational wave detector Hanford WA 4km A really BIG light interferometer!

de Broglie Wave Interference Neutron interference MICHIGAN 1975 = h/mv = de Broglie wavelength Particle wavepacket Atoms (v~1m/s): Compare with light waves: Shorter wavelength a more sensitive ruler!

Atom Interferometer Force Sensors Gravity/Accelerations gravity LONGER de Broglie wavelength As atom climbs gravitational potential, velocity decreases and wavelength increases (Rotations also sensed) The quantum mechanical wave-like properties of atoms are used to sense inertial forces. SHORTER de Broglie wavelength

Gravimetry MASSIVE BLOB Gravitational force ~ mass (distance) 2

Example: Light-Pulse AI Gravity Gradiometer Mirror Atom s L a s e r B e a m 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 G. McGuirk, M. Kasevich

Laboratory validation: Mass Detection Pb bricks Lower accelerometer Sample number (1 sample/sec) Gradient (arb. units) Modulated acceleration signal due to 8 lead bricks near lower accelerometer. Green o,+: upper/lower accelerometer outputs Blue: Gradient signal Successful laboratory demonstration of mass anomaly detection capabilities G. McGuirk, M. Kasevich

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 Earth’s gravity field LM UGM

II. Quantum Tornadoes Near Absolute Zero Courtesy NOAA Plus ….what kind of thermometer measures the coldest places in the universe anyways?

Hot cloud Images of clouds How to make a thermometer for cold atoms Let the gas expand Cold cloud