July 2022
Abstracts of the QSIT/Quantum Center, ETH Zürich Lunch Seminar, Thursday, July 7, 2022
Nanoparticle Levitation in a Hybrid Paul-Optical Trap
Eric Bonvin - Photonics Laboratory (Novotny group), ETH Zurich
Optical traps provide a high level of control over levitated nanoparticles, making it possible to cool the center-of-mass motion of macroscopic objects to the quantum ground state [1, 2]. However, the high optical intensities required to trap generate a significant amount of back action. In contrast, radio-frequency Paul traps constitute an alternative trapping technique characterized by much weaker traps but also much less back action. We describe our hybrid trapping setup which consists of an optical trap paired with a high optical access Paul trap allowing us to trap the same particle at the same point in space using two different methods [3, 4].
This setup will allow us to use optical trapping for state preparation, before rapidly transferring the particle to the Paul trap for state evolution in the absence of an optical field. Through this process, we aim to measure coherent expansion of an optically cooled nanoparticle, and we hope to learn about heating contributions other than the optical trapping field.
[1] L. Magrini et al., Nature 595 (7867): 373–77 (2021)
[2] F. Tebbenjohanns et al., Nature 595 (7867): 378–82 (2021)
[3] G. Conangla et al., Nano Letters 20 (8): 6018–23 (2020)
[4] D. Bykov et al., arXiv:2204.04912 (2022)
Towards surface NMR using Nitrogen-Vacancy Centers in diamond
Konstantin Herb – Spin Physics Group (Degen group), ETH Zurich
Nitrogen-Vacancy centers are the workhorse for nanoscale nuclear magnetic resonance (NMR) spectroscopy and imaging. While impressive results have been achieved on performing spectroscopy and mapping of 13C spins in the diamond, the sensing capability of near-surface NVs is severely limited by charge state instabilities and decoherence due to surface traps and electronic/magnetic noise, respectively.
In this talk, we report on recent strategies to improve NMR spectroscopy methods towards the long-term goal of imaging individual molecules that are attached to the diamond surface. From the sample side, we report on our ongoing work on bringing NV centers close to the surface and preparing surfaces in a controlled manner. We chemically functionalize the diamond surface with monolayers of fluorinated molecules and show that 19F NMR signals can be detected using single NVs. We give an outlook on the steps needed to perform NMR measurements at the single-molecule level and to expand the suite of characterization methods necessary for spin mapping above the diamond surface.