Within the IQLev project, we have been extending and perfecting levitated systems toolbox and demonstrating the potential of this technology for inertial sensing. Our most prominent achievements in optical, electrostatic and magnetic levitated sensors development include:
Hybrid optical-electrostatic on-chip accelerometer
Optically levitated nanoparticles are promising candidates for force and inertial sensing applications owing to their high level of isolation under UHV conditions and their relatively high mass. To integrate their acceleration sensing capabilities onto a compact and robust platform, we developed a hybrid chip combining optical and electrostatic trapping potentials. The developed platform allows today for the stable levitation of 415nm particles at 10-6 mbar, leading to an acceleration sensitivity of the order of 50 μ/√. Further immediate improvements related to pressure and particle size promise an additional order of magnitude improvement.
Magnetically levitated accelerometer
We have developed a platform for acceleration sensing that uses levitated superconductors in a magnetic field gradient and performs the read-out via superconducting quantum interference devices (SQUID). This platform has several advantages over optically levitated systems, including a higher mass of a levitated object, low intrinsic damping of the superconductor (Q ~ 26 mill), and cryogenic temperatures of 20 mK. These features enabled the quantification of the thermally limited inertial noise density to be 9 ⋅ 10^-12 /√.
Additional information regarding this platform is available at
Hofer et al, to appear in Phys. Rev. Lett. (2023)(öffnet in neuem Fenster).
Optically levitated gyroscopes
We are working towards a gyroscope based on a spinning anisotropic nanoparticle trapped in optical tweezers. Thanks to extremely high rotational speeds achievable with optically levitated particles (reaching several GHz), this design will allow us to mitigate the sensitivity limitation arising from mass constraints in optical levitation. In order to develop the prototype gyroscope, we created new tools for controlling the rotational degrees of freedom of optically levitated objects. By using an optical beam with variable degree of polarization for levitation, we have demonstrated an “optical gimbal mount” (more details in Zielinska et al, Phys. Rev. Lett. 130, 203603, 2023). Additionally, our platform allows for controlling spinning motion of the nanodumbbell around both short and long axes of the particle. Our current operating parameters translate into thermal-limited gyroscope sensitivity (angular random walk) of 4 × 10 ^-6 rad/s/√Hz.
Towards quantum-enhanced inertial sensing
The IQLev consortium has experimentally shown that optically levitated systems are on the brink of entering the quantum regime (see Magrini et al, Nature 595, 373–377, 2021; Tebbenjohanns et al Nature 595, 378–382, 2021). In the future this will lead to new exciting opportunities for high-performance inertial sensing using quantum (e.g. squeezed) states of mechanical degrees of freedom. In order to guide experimental efforts, we have developed a theoretical formalism to further understand how the electromagnetic field interacts with levitated particles of arbitrary size in the quantum regime (see Maurer et al, arXiv:2106.07975 [quant-ph], 2021) . We are also building a theoretical toolbox to enable platform-independent modeling of quantum dynamics of largely squeezed quantum states and their optimization. We believe our theoretical advances are paving the way for smart quantum sensing techniques, particularly for based on hybrid optical-electrostatic levitation.
The IQLev consortium has dedicated a substantial effort to disseminating and promoting the results to scientific, industry, and lay audiences. The lay audiences were targeted through public events, publications, and social media. These channels allowed us to effectively communicate our research in a manner that is accessible and engaging to the general public. The dissemination of our work to professional audiences, (including academics and industry experts) is accomplished via publications (which are made available in an open-access repository) and our participation in conferences. In terms of exploitation, the expertise gained through IQLev to is of crucial importance for supporting additional research projects and as a foundation for fellowship applications. The consortium members are planning to continue advancing the technology created as part of this project.
