Another Wavelength: Kali Wilson

    Date Posted: 
    Tuesday, December 16, 2014

    This month's student on Another Wavelength is seventh-year Ph.D. candidate Kali Wilson. Originally from Morgantown, West Virginia, she received a bachelor's degree in physics from Wellesley College in 2004.

    Another Wavelength banner with photo of Kali Wilson

    What brought you to optics?

    I've always been interested in intellectual puzzles and building things, so when I had my first introduction to an optical physics lab as an REU student, I felt right at home. I am intrigued by the optical physics questions but also enjoy the experimental techniques that enable the physics, so I enjoyed the mix of design, building equipment and basic science that I encountered. Sometimes I feel like lab work is just playing with a more expensive version of the erector set that I had as a child.

    Kali Wilson reclines in a tree outside the Meinel BuildingWho would you call your science hero?

    One of my heroes in science is James Clerk Maxwell. I am impressed by the breadth of his physical insight. He made significant contributions to almost every important physics question of his time, from electricity and magnetism, to the way humans perceive color, to statistical mechanics. He was brilliant, and he was a nice person. Now if only I could get Maxwell's equations to stick in my head.

    Describe your research in 20 words or fewer.

    I study the fluid dynamics of tiny, very cold, superfluid droplets of atoms called Bose-Einstein condensates.

    Describe your research in 200 words or fewer.

    I work with Dr. Brian Anderson, studying superfluid vortices and quantum turbulence in Bose-Einstein condensates. My current project involves upgrading our optical system to enable minimally destructive in situ observation of vortex distributions.

    Images of Bose-Einstein condensates

    Just as eddies and whirlpools comprise classical turbulent flows, quantum vortices are basic elements of quantum turbulence. In particular, a quantized vortex represents a specific pattern of circular fluid flow within the condensate. Due to the single-valued nature of the wavefunction, a vortex is observed as a sharp dip in the bulk density of the BEC; for our experimental parameters, the diameter of a vortex is approximately 0.5 micrometers, whereas the BEC diameter is approximately 100 micrometers. In an in situ bright-field image the vortex is a tiny transmission feature, easily lost in the noise. Standard vortex imaging techniques involve releasing the BEC from the trap and imaging after a period of expansion when the vortices are more easily resolved. This method is both destructive and limited to certain trapping geometries, limiting observations of the dynamics of the superfluid. I am exploring using dark-field imaging to isolate the vortex signal from that of the bulk BEC and allow for imaging in situ.

    Name three neat facts about you.

    1. I bake an excellent chocolate mousse cake.
    2. I used to raise milk goats.
    3. I once made the brilliant decision to ford a river four times in a rental car in Iceland. It was exciting and, as it turned out, unnecessary.


    Figure courtesy of Kali Wilson. The leftmost two images show a vortex lattice in a BEC after a period of expansion; the first is imaged in dark field and the second is an example of bright-field imaging. The rightmost two images show vortex distributions that arise after stirring the BEC with a laser beam.