Jerzy Zachorowski

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Nonlinear Spectroscopy of Cold Atoms,
Preparations for the BECExperiments

• Jerzy Zachorowski
• M. Smoluchowski Institute of Physics,
• Jagiellonian University

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The Group
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Magneto-Optical Trap

85Rb N ? 108 T ? 100 ?K
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Spectroscopy of Cold Atoms
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Laser system
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Central Structure

• Raman transitions between light-shifted Zeeman
  sublevels
• Raman transitions between vibrational levels in
  the optical lattice

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Zeeman sublevels
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Vibrational levels

• Electric field in the trap 6 beams of different
  polarizations.
• Relative phases not fixed, but relatively stable.
• Interference intensity and/or polarization
  modulation.
• Additional optical forces (dipole forces).
• Atoms cooled and localized in the lattice nodes.
• Atomic movement quantized vibrational energy
  levels.

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Remarks
New experiments trap modulation
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Bose-Einstein Condensation

• de Broglie wavelength

density n, distance n1/3, condensation when
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Lower temperatures

• Spontaneous emission temperatures limited to 10
  1mK
• Dark traps optical dipole or magnetic forces
• Cooling by evaporation

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Three steps to BEC
1. Magneto-Optical Traptemperature 10 mK,
density 1010 cm-3limit interaction with light.
2. Magnetic Traptrap in field minimum - only
low-field-seeking stateslosses at B 0.
3. Evaporation coolingforced evaporation of hot
atoms, thermalisation by collisions.
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1995 - E. Cornell C. Wieman Rb87
50 nK
200 nK
400 nK

• Evidence
• narrow peak in velocity distribution
• peaks amplitude ? when T?
• cloud shape same as that of the potential well

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Now
Over 30 laboratories produce BEC 87Rb, 23Na, 7Li,
?H , He, ...  
Experiments with BEC

• Matter-wave optics condensate interference, atom
  laser
• Nonlinear atom optics
• Superfluidity, vortices
• Ultra-low density condensed-matter Mott
  insulator
• Cold fermions

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Matter-wave Optics Atom Optics
coherent waves ? interference
?atom laser
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Nonlinear atom-optics
1999 NIST (W. Phillips) Marek Trippenbach (UW)
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Superfluidity, Vortices
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Ultra-low density condensed-matter
Mott transition
MPQ Garching
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Micro-BEC
6000 87Rb atoms loading time 8 s cooling time
2,1 s current 2A
Garching
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Micro-BEC 2
Tubingen 87Rb Number of atoms in BEC
106 Condensation at T1mK Cooling time 27s
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Cold fermions
Do not thermalize (Pauli exclusion) Sympathetic
coolinge.g. fermion 40K boson 87Rb, fermion
6Li boson 7Li
2001 R. Hulet (Rice)
1999 D. Jin (JILA) 40K
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Our way towards BEC
Element 87Rb
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Transfer of atoms

• repetitive pushing by resonant light beam,
  recapture in lower MOTcollection speed 1081010
  s-1loading of lower MOT 107109 s-1
• constant pushing by narrow light beam (Dalibard)
  flux 108 s-1
• magnetic transfer directly into magnetic trap
  (Hänsch)30 efficiency, complicated.

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Magnetic traps
QUIC Quadrupole Joffe configuration B ? 0
at trap center
Dalibard
Hänsch
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September 2002

• Laser system prepared
• Upper MOT ready operating
• Next steps transfer recapture magnetic
  trapping