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The Bose-Einstein Condensate

The Bose-Einstein Condensate. Jim Fung Phys 4D. Bose-Einstein Condensate (BEC). Postulated by Bose and Einstein in 1924. Forms when less than 500 billionths of a Kelvin above Absolute Zero. Forms “superatom” in which no individual atom can be identified. BEC continued.

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The Bose-Einstein Condensate

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  1. The Bose-Einstein Condensate Jim Fung Phys 4D

  2. Bose-Einstein Condensate (BEC) • Postulated by Bose and Einstein in 1924. • Forms when less than 500 billionths of a Kelvin above Absolute Zero. • Forms “superatom” in which no individual atom can be identified.

  3. BEC continued • Previously, the coldest temperatures able to be produced were with initial cooling with He and then magnetic cooling. • In 1995, Bose condensation was observed when rubidium was cooled to 100nK

  4. Two BEC overlapping, interference pattern

  5. How do you make it? • Cool with laser light until 1/10000 degrees above absolute zero. • Bombard atoms from all sides, forming an “Optical molasses”. • Photons are absorbed by the atoms and released with a blue shift relative to the laser, indicating that the photons gained energy. • Doppler Effect. • Magnetic field assists the laser trap.

  6. So is that all we need? • No! The lowest temperature that light can slow the atoms down to is 1/10000K. • Due to fact that a photon gives a certain minimum kick to an atom when it collides. • We need evaporative cooling.

  7. Evaporative Cooling • Form a magnetic trap in which the atoms are contained. • BEC atoms have one free valence atom and thus have magnetic moment. • BEC cannot occur for atoms with odd sum for p+n+e. • Allow more energetic atoms to escape the collection. • High energy particles are accelerated away by finely tuned E/M waves.

  8. So what do you mean it slows down light? • Speed of photons is c. • Light is macroscopically slowed when passing through a medium. • Light propagates through a substance by atomic absorption and reemission, thus slowing its apparent speed.

  9. Speed of Light Substance Speed of light (m/s) Vacuum 299792458 Air(0°C) 299704600 Water(20°C) 225000000 Glass 190000000 Diamond 123900000 Bose-Einstein Condensate 17

  10. Properties/Applications • Optical communication (fiber optics). • Quantum computing. • Study quantum interactions – superatoms exhibiting observable wave interference. • Atom lasers.

  11. Atom laser accelerated by gravity

  12. BEC is to matter as laser is to light. • Expect to see great developments in BEC technology and application. • Lasers at first were thought to be too difficult to use practically and it took 20 years to become viable and look at the advances in technology that have come about from it! BEC has the potential to do the same in the future!

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