Physics Department Faculty:
Lene V. Hau
Mallinckrodt Professor of Physics and of Applied PhysicsPhD 1991, Aarhus, Denmark
Lene Hau's latest research has centered on cold atoms and
Bose-Einstein condensation. Her group uses laser cooling
to efficiently precool atoms to temperatures in the microkelvin
regime. Subsequently, the atoms are trapped in a 4 Dee magnet
and evaporatively cooled to nanokelvin temperatures, which
results in the creation of Bose-Einstein condensates typically
containing millions of atoms. The condensates are formed
in an ultra high vacuum system constructed for easy access
to and manipulation of cold atom clouds with light probes
and mechanical structures.
Recently, the Hau group succeeded in reducing the light speed
to 17 m/s (the speed of a racing bicycle) by optically inducing
a quantum interference in a Bose-Einstein condensate. Ultra
slow light creates a unique, new tool for probing the fundamental
properties of Bose-Einstein condensates. Examples are: coupling
of light and sound, an atom laser with controllable, localized
output coupling, and studies of the dynamical formation of
condensates. The system also exhibits extreme optical properties:
Hau's group has demonstrated a nonlinear refractive index
which is 14 orders of magnitude larger that the nonlinear
index in an optical fiber and the largest ever measured by
a factor of a million.
This has opened up a new territory of nonlinear optics at extremely low light levels, with interesting prospects for areas of quantum optics such as optical squeezing, quantum nondemolition, and studies of nonlocality. Intriguing potential applications of the large nonlinearities include creation of optical switches that work at the single photon level, dynamically programmable optical delay lines, and serial to parallel conversion.
A practical system could possibly be based on atom cooling with the use of diode lasers and micro-traps relating to another of Hau's interests: atomic wave guides for cold atoms. Hau and collaborators were the first to suggest a wave-guide for cold atoms based on a mechanical structure. The suggested "Kapitza guide" involves dynamical stabilization of atom motion around a metallic wire with time varying electric potentials. The resulting atom dynamics is intriguing and coupled with Bose-Einstein condensates, the wave-guide offers a unique possibility for studying chaos in a many body, interacting system. Furthermore, a condensate could adiabatically be transferred from the 4 Dee magnet to the wave-guide states, leading to output coupling and transport of coherent atomic matter waves. The Kapitza guide can thus be regarded as the matter wave analogue of optical fibers used as guiding structures for coherent light.
- L.V. Hau, S.E. Harris, Z. Dutton, and C.H. Behroozi, "Light speed reduction to 17 metres per second in an ultracold atomic gas". Nature 397: 594 (1999).
- L.V. Hau, B.D. Busch, C. Liu, Z. Dutton, M. M. Burns, and J.A. Golovchenko, "Near resonant spatial images of confined Bose-Einstein condensates in the '4 Dee' magnetic bottle". Phys. Rev. A 58: R54 (1998).
- L.V. Hau, B. D. Busch, C. Liu, M. M. Burns, and J. A. Golovchenko, "Cold atoms and creation of new states of matter: Bose-Einstein condensates, Kapitza states, and '2D magnetic hydrogen atoms'", in Photonic, Electronic, and Atomic Collisions, Invited Talks at the XX.ICPEAC, Vienna, Austria, July, 1997, eds F. Aumayr and H.P. Winter (World Scientific, Singapore, 1998).
- L.V. Hau, J.A. Golovchenko, and M. M. Burns, "Supersymmetry and the binding of a magnetic atom to a filamentary current". Phys. Rev. Lett. 74: 3138 (1995) (See also: Phys. Rev. Lett. 75: 1426 (1995) for corrections of typesetting errors in the original version ).
- L.V. Hau, M. M. Burns, and J.A. Golovchenko, "Bound states of guided matter waves: An atom and a charged wire". Phys. Rev. A 45: 6468 (1992).