Investigating surface interactions with levitated optomechanics at the quantum limit
Abstract
Abstract: Levitated optomechanics has great potentials in precision sensing andmetrology, thermodynamics, macroscopic quantum mechanics, and quantum information science.In this project, we will optically trap and cool a nanodumbbell in vacuum, and develop an ultrasensitive probe to study surface interactions. Different from a nanosphere, a levitated nanodumbbell can couple to the angular momentum of photons, and can detect both force and torque. It will be several orders more sensitive than current state-of-the-art nanoscale torsion balances in torque detection. A levitated nanodumbbell near a birefringent plate or a nanostructured surface will enable us to measure the anisotropic Casimir force and the Casimirtorque, and provide essential understandings of the interactions between anisotropic materials and structures.The other major goal of this project is to cool at least one motional mode of a levitated nanosphere in vacuum to quantum ground state with a systematic approach. Ground state cooling is required to fully explore the benefits of levitated optomechanics for many applications. The bottleneck in achieving ground state cooling of a levitated nanoparticle with feedback has beeninefficient signal collection with traditional lenses inside a vacuum chamber. In this project, we will first use a pair of high numerical aperture (NA) infrared objective lenses to focus and detecta 1064 nm ultrastable laser, and cool the motion of a nanoparticle to near the ground state.Meanwhile, we will use advanced nanofabrication techniques to develop optimized high NA, high efficiency objective lenses to collect signals to achieve ground state cooling. Different from traditional lenses, a nanostructured lens can be designed to selectively collect the light that contains the most information, while rejecting the undesirable part of the light that mainly contributes to the shot noise in detection.This proposal is based on our recent breakthroughs that Prof. Li???s group has assembled silica nanodumbbells and optically trapped them in high vacuum. Different from a nanosphere, a nanodumbbell has anisotropic optical properties. We have observed the torsional vibration of an optically levitated nanodumbbell and driven it to rotate at high speed beyond 1 GHz for the first time. These results provide a solid foundation for this project. Co-PI Prof. Robicheaux???s grouphas performed quantum calculations of feedback cooling, and will do theoretical investigations to guide key steps of experiments and to analyze results. Co-PI Prof. Ni has used nanostructured surfaces to bend broadband light and create ultrathin lenses. His group will be able to rapidly develop surface lenses for this project.The proposed researches align well with ONR???s interests in high-precision metrology and sensing, quantum optomechanics, and coherent control of quantum systems. As described in ???ONR Basic Research Challenge Topic 2: Levitated Optomechanics???, levitated nanoparticles in vacuum will be extremely sensitive detectors. In this project, (1) we will trap and cool a levitatednanodumbbell in vacuum, and demonstrate precision force and torque sensing with it. (2) We will investigate surface electrostatics and the Casimir interactions with a levitated nanodumbbell near a birefringent plate or a nanostructured surface. (3) We will cool the motion of a levitated nanoparticle to the quantum ground state with the help of nanofabricated lenses. Ground state cooling is a major goal of this ONR BRC topic, and will allow us to experimentally explore theclassical and quantum boundary. Our work will broaden the research base in support of U.S. national defense.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jul 10, 2018
- Source ID
- N000141812371
Entities
People
- Tongcang Li
Organizations
- Office of Naval Research
- United States Navy
- University of Virginia