Benjamin Siegel successfully defends thesis, “Arrays of Optomechanically Levitated Microspheres”

On March 3, Benjamin Siegel successfully defended the thesis “Arrays of Optomechanically Levitated Microspheres” (advisor: David Moore).

Siegel explained, “In particle physics, precision measurements using tabletop experiments have grown as complementary approaches to the large collaborations in searching for deviations from the Standard Model. Levitated optomechanical systems offer a promising platform for such measurements with their extreme force and acceleration sensitivity. By optically trapping objects in vacuum and controlling their motion and physical attributes, such as net charge, we can achieve excellent isolation from the environment. This has allowed us to search for beyond the Standard Model interactions with the object as a whole, as opposed to interactions on the nuclear or atomic scale, and it has already resulted in new constraints on the properties of dark matter.”

Siegel continued, “Levitated optomechanics is a relatively new and rapidly developing field. Thus far, experiments have demonstrated simultaneous levitation of only a handful of objects. The aim of my research is to realize large arrays of levitated objects for improving the sensitivity of beyond the Standard Model physics searches.”

Siegel will next join TU Wien’s Atominstitut as a postdoc working with levitated nanospheres. 

Thesis Abstract: Levitated microspheres have proven to be extremely sensitive force and momentum detectors, enabling searches for physics beyond the Standard Model. By monitoring the position and charge of such spheres, our lab has already set limits on relic millicharged particles, searched for composite dark matter and detected nuclear decays through mechanical recoils. We plan to improve the sensitivity of these rare event experiments by scaling to an array of traps. Using a time division multiplexing approach for creating the array enables independent control over each trap. We have successfully demonstrated trapping and reorganization of up to 49 spheres, with their motion monitored via a high speed camera. Furthermore, we have realized a scalable real-time feedback protocol that is currently limited by the bandwidth of our photodiodes and acousto-optic deflectors. This protocol utilizes back focal plane imaging and backscattered light detection and will be able to independently cool the center-of-mass motion of each sphere. In the future, this setup will increase our cross section for dark matter scattering events, with the added benefit of improving noise rejection via correlated motion of the array.

Thesis committee: David Moore (advisor), Jack Harris, Charles Brown, Ian Moult, Uros Delic (TU-Wein, Austria)