arXiv subjects

Tobias Reiter

Publications and source records attributed to Tobias Reiter.

3 recordsLinked to original sources

arXiv2023

Triggered Superradiance and Inversion Storage in a Hybrid Quantum System

We study the superradiant emission of an inverted spin ensemble strongly coupled to a superconducting cavity. After fast inversion, we detune the spins from the cavity and store the inversion for tens of milliseconds, during which the remaining transverse spin components disappear. Switching back on resonance enables us to study the onset of superradiance. A weak trigger pulse of a few hundred photons shifts the superradiant burst to earlier times and imprints its phase onto the emitted radiation. For long hold times, the inversion decreases below the threshold for spontaneous superradiance. There, the energy stored in the ensemble can be used to amplify microwave pulses passing through the cavity.

quant-ph↗

arXiv2023

Tractor beams with optimal pulling force using structured waves

Moving objects with optical or acoustical waves is a topic both of fundamental interest and of importance for a range of practical applications. One particularly intriguing example is the tractor beam, which pulls an object toward the wave's source, in opposition to the wave's momentum. In this study, we introduce a protocol that enables the identification of wave states that produce the optimal tractor force for arbitrary objects. Our method relies solely on the solution of a simple eigenvalue problem involving the system's measurable scattering matrix. Using numerical simulations, we demonstrate the efficacy of this wavefront shaping protocol for a representative set of different targets. Moreover, we show that the diffractive nature of waves enables the possibility of a tractor beam, that works even for targets where a geometric optics approach fails to explain the pulling forces.

physics.optics↗

arXiv2022

Modeling Incomplete Conformality during Atomic Layer Deposition in High Aspect Ratio Structures

Atomic layer deposition allows for precise control over film thickness and conformality. It is a critical enabler of high aspect ratio structures, such as 3D NAND memory, since its self-limiting behavior enables higher conformality than conventional processes. However, as the aspect ratio increases, deviations from complete conformality frequently occur, requiring comprehensive modeling to aid the development of novel technologies. To that end, we present a model for surface coverage during atomic layer deposition where incomplete conformality is present. This model combines existing approaches based on Knudsen diffusion and Langmuir kinetics. Our model expands the state-of-the art by (i) incorporating gas-phase diffusivity through the Bosanquet formula as well as reaction reversibility in the modeling framework first proposed by Yanguas-Gil and Elam, and (ii) being efficiently integrated within level-set topography simulators. The model is manually calibrated to published results of the prototypical atomic layer deposition of Al$_2$O$_3$ from TMA and H$_2$O in lateral high aspect ratio structures. We investigate the temperature dependence of the H$_2$O step, thus extracting an activation energy of $0.178\,\mathrm{eV}$ which is consistent with recent experiments. In the TMA step, we observe increased accuracy from the Bosanquet formula and we reproduce multiple independent experiments with the same parameter set, highlighting that the model parameters effectively capture the reactor conditions.

physics.comp-ph↗