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Quantum Control of a Levitated Nanoparticel in a Microcavity

Periodic Reporting for period 1 - QNaMic (Quantum Control of a Levitated Nanoparticel in a Microcavity)

Reporting period: 2016-10-01 to 2018-09-30

Arthur Ashkin received the 2018 Nobel Prize in Physics for the invention of the optical tweezers. The high level of control with which optical tweezers can manipulate minute objects rendered the work of Ashkin highly relevant for applications in biological systems and medicine. The project QNaMic (Quantum Control of a Levitated Nanoparticel in a Microcavity) was built on the achievements of Ashkin and utilized light to control mechanical objects at the ultimate level. Such well-controlled mesoscopic devices will illuminate fascinating questions of modern physics connected to the quantum to classical transition or to mesoscopic thermodynamics. Technologically, these optomechanical devices are foreseen to serve as transducers in future quantum communication networks and in high-precision sensing. The techniques and devices developed in QNaMic will therefore hugely benefit our society via future emerging technologies.

QNaMic developed a novel and highly controlled mesoscopic device, realized by an optically levitated nanoparticle coupled to a small cavity under ultra-high vacuum. The multidisciplinary project combined methods from control theory, cavity optomechanics, and cold atom experiments: A trapped nanoparticle, precooled by cavity cooling, is coupled to a high-finesse cavity, which tremendously improved the measurement sensitivity and allows for studies in the realm of mesoscopic quantum mechanics. QNaMic is also designed for studies of very weak forces or mesoscopic thermodynamics and furthermore permits coupling to external systems in the context of quantum communication.
QNaMic aimed at developing a novel technological platform in form of a highly controlled, ultra-sensitive cavity device. This aim has been reached. We have designed and built an experimental setup consisting of a loading chamber, a transfer scheme into a science chamber and an optical cavity with small mode volume in the science chamber. After optically trapping the particle in the loading chamber, a mechanical transfer scheme places it with nm precision in the optical cavity which measures and controls the particle position with unprecedented precision. Currently the QNaMic team writes a high impact publication covering those results.

Additionally, QNaMic did not only investigate the linear motion of an optically trapped particle, but also studied the light induced rotation of the particle. We found that the particle can spin at a world-record rotation speed of 1 billion rotations per second. Such a rapidly spinning nanoprobe allows for stress tests of materials on the nanoscale. In the field of material science, these tests are relevant for finding fundamental material stress limits and for material optimization. These results of an ultra-fast spinning particle have been published in a high impact journal [‘GHz Rotation of an Optically Trapped Nanoparticle in Vacuum’ [Phys.Rev. Lett. 121, 033602 (2018), also arXiv:1803.11160]]. This publication triggered an extremely high public interest and has be covered by more than 10 public outreach platforms.
Both main results of QNaMic (particle control in cavity and ultra-fast rotation) significantly advanced the state of the art of levitated optomechanical systems and form a solid basis for further experimental advances in the young but technologically highly relevant field of levitodynamics.

The results of the ultra-fast rotation were explained to the public in layman’s term (see e.g. ‘Physik in unserer Zeit’, Title: Das schnellste rotierende Objekt der Welt; Publication in volume 6/2018 which advanced the public understanding of the importance of the research conducted in QNaMic.

The students (more than 10) who have been trained within QNaMic, received a solid education in the fields of precision optics, low-noise electronics, vacuum systems, data acquisition and evaluation, and last but not least in rigorous scientific thinking and working in a team. Those students are now equipped with the skill set which is essential to advance the high-tech countries of the European Union.