Short-range force detection using optically-cooled levitated microspheres (1006.0261v2)

Abstract: We propose an experiment using optically trapped and cooled dielectric microspheres for the detection of short-range forces. The center-of-mass motion of a microsphere trapped in vacuum can experience extremely low dissipation and quality factors of $10^{12}$, leading to yoctonewton force sensitivity. Trapping the sphere in an optical field enables positioning at less than 1 $\mu$m from a surface, a regime where exotic new forces may exist. We expect that the proposed system could advance the search for non-Newtonian gravity forces via an enhanced sensitivity of $10^5-10^7$ over current experiments at the 1 $\mu$m length scale. Moreover, our system may be useful for characterizing other short-range physics such as Casimir forces.

• The paper demonstrates that optically cooled levitated microspheres achieve yoctonewton force sensitivity in ultrahigh vacuum, enabling near-surface force measurements.
• The method employs dielectric spheres trapped and cooled in optical cavities to minimize damping and reach quality factors exceeding 10^12.
• This enhanced detection capability paves the way for probing non-Newtonian gravitational forces and other nanoscale interactions like Casimir forces.

Short-range Force Detection Using Optically-cooled Levitated Microspheres

The paper "Short-range force detection using optically-cooled levitated microspheres" by Geraci, Papp, and Kitching presents an innovative approach to detect short-range forces by employing optically controlled dielectric microspheres. These dielectric microspheres, when trapped and cooled in an optical vacuum cavity, can be brought extremely close (less than 1 µm) to a surface, facilitating the detection of forces at previously inaccessible scales.

The methodology employed centers around the optical trapping of dielectric microspheres, a technique originally advanced by Ashkin and coworkers in the 1970s, and which has since proliferated across various fields such as biophysics and condensed-matter physics. The advancement proposed here explores trapping in ultrahigh vacuum conditions, theoretically providing exceptional mechanical quality factors ($Q$) exceeding $10^{12}$, which correspond to yoctonewton-sensitive force detection. This unprecedented force sensitivity is achieved as a result of significantly reduced thermal and viscous damping, which are characteristic outcomes when operating in a vacuum environment.

The potential impact of this work is notable in the context of probing non-Newtonian gravitational forces. The authors detail how their proposed optical system could enhance the sensitivity to such forces by factors of $10^5-10^7$ over existing experimental arrangements at the 1 µm scale. The proposed experiment is adept at measuring deviation from Newtonian gravity that may result from phenomena like extra spatial dimensions or gauge-mediated supersymmetry breaking. Additionally, this setup is also conducive to exploring other fundamental physical interactions, such as Casimir forces and radiative heat transfer at the nanoscale.

A pivotal aspect of this experiment involves the practical realization of trapping dielectric spheres in cavities, cooling them, and utilizing optical techniques to measure their mechanical motion with high precision. This setup allows for the exploration of forces and interactions at the nano- to micrometer scale with nanoscale precise control. The system leverages low finesse optical cavities to damp and measure the center of mass motion of the spheres, counteracting ambient thermal noise.

Parametrizing the corrections to Newtonian gravity through a Yukawa potential, the experiment aims to ascertain the interaction strengths and ranges by measuring force gradients at micron scales. Such efforts have the potential to redefine fundamental physics at these distances. Moreover, by encapsulating the experimental apparatus with a gold-coated silicon nitride membrane, diffraction force gradients like the Casimir force can serve as a systematic perturbation aiding in understanding and isolating such gravitational interactions.

In summary, this paper contributes substantially to the feasibility of employing optically-cooled levitated microspheres for short-range force detection. It outlines a methodology that stands to shed light on high precision force measurements, paving the way for deeper insights into fundamental interactions at the nanoscale. These contributions are expected to have profound implications across fields dealing with micro- and nanomechanical systems, with potential extensions into advancing theoretical physics paradigms and the detection of exotic forces beyond current observation capabilities. Future advancements may include extension to cryogenic environments for further sensitivity enhancement, underscoring the dynamic potential of optically-cooled microsphere systems in advancing the frontiers of experimental physics.