Synopsis

How to Focus a Bose-Einstein Condensate in a Waveguide

Physics 14, s55
A new “lensing” technique counters the spreading of an ultracold cloud of atoms inside a tiny waveguide.
S. Pandey et al. [1]

An ultracold cloud of atoms spreads with time, just as a beam of light spreads in space, but an electromagnetic “lens” can “focus” the cloud and reduce its kinetic energy. The lowest energies yet achieved—in the picokelvin (pK) range—require large facilities that allow the atoms to fall freely for several seconds. Now researchers have demonstrated a lens that works in this regime with atoms in a ring-shaped waveguide less than a millimeter across [1]. Manipulating these “matter waves” in small spaces is essential for exploiting their quantum effects for purposes such as high-precision navigation.

The team, led by Wolf von Klitzing at the Institute for Electronic Structure and Lasers, part of the Foundation for Research and Technology - Hellas in Greece, placed a several-hundred-micrometer-wide Bose-Einstein condensate (BEC) of rubidium atoms into a ring-shaped electromagnetic trap, somewhat like placing a marble in a roulette wheel. To start the “marble” moving, the team tilted the ring toward the atoms and then rotated it about its original vertical axis, so that the lowest point revolved at up to 10 Hz for about 200 ms. Next, they leveled the ring and let the cloud spread freely as it raced around. Finally, the team focused the BEC by again tilting the rotating ring toward the atoms for 17 ms.

The researchers showed that the tilt angle was analogous to the focusing strength of an optical lens. Too large a tilt caused the cloud to briefly shrink and then enlarge, like an overly powerful lens focusing light in front of the intended focal plane. The ideal tilt of about 5° held the cloud at a fixed size for nearly a second and reduced its expansion energy to 800 pK.

–David Ehrenstein

David Ehrenstein is a Senior Editor for Physics.

References

  1. S. Pandey et al., “Atomtronic matter-wave lensing,” Phys. Rev. Lett. 126, 170402 (2021).

Subject Areas

Atomic and Molecular Physics

Related Articles

Superpositions of Chiral Molecules
Chemical Physics

Superpositions of Chiral Molecules

Matter-wave diffraction can put chiral molecules into superpositions of left- and right-handed forms, enabling new studies of how the two states interact with their environment. Read More »

3D Collimation of Matter Waves
Atomic and Molecular Physics

3D Collimation of Matter Waves

An innovative matter-wave lens exploiting atomic interactions is able to slow the expansion of a Bose-Einstein condensate in three dimensions, thus reaching unprecedented ultralow temperatures. Read More »

3D-Printed Components for Cold Atoms
Quantum Physics

3D-Printed Components for Cold Atoms

Researchers demonstrate lighter, smaller optics and vacuum components for cold-atom experiments that they hope could enable the development of portable quantum technologies. Read More »

More Articles