arXiv subjects

David Bachmann

Publications and source records attributed to David Bachmann.

5 recordsLinked to original sources

arXiv2024

Accurate Zernike-Corrected Phase Screens for Arbitrary Power Spectra

Wave propagation through random continuous media remains an important fundamental problem with applications ranging from remote sensing to quantum communication. Typically, such media are characterized by smooth refractive index fluctuations whose impact on the wave can be captured by the stochastic parabolic equation. The latter can be solved numerically by means of a split-step method, which replaces the continuous medium with a number of discrete phase screens derived from the medium's power spectrum. We introduce and benchmark highly accurate and efficient hybrid phase screens for arbitrary power spectra which are based on the combination of Zernike and Fourier phase screens.

physics.optics↗

arXiv2023

Meron configurations in easy-plane chiral magnets

We demonstrate the existence and study in detail the features of chiral bimerons which are static solutions in an easy-plane magnet with the Dzyaloshinskii-Moriya (DM) interaction. These are skyrmionic textures with an integer topological charge and they present essential analogies to the meron configurations introduced in the context of quark confinement in the O(3) nonlinear sigma-model. We employ a Moebius transformation to show that, for weak chirality, bimeron configurations approach Belavin-Polyakov (BP) solutions characterized by tightly bound vortex and antivortex parts of the same size. Stronger chirality induces different vortex and antivortex sizes and also a detachment of merons, suggesting the possibility for a topological phase transition. Exploiting the fact that bimerons of opposite topological charges may exist in the same material, we demonstrate numerically a mechanism to generate meron pairs.

cond-mat.mes-hall↗

arXiv2022

Universal crosstalk of twisted light in random media

Structured light offers wider bandwidths and higher security for communication. However, propagation through complex random media, such as the Earth's atmosphere, typically induces intermodal crosstalk. We show numerically and experimentally that coupling of photonic orbital angular momentum (OAM) modes is governed by a universal function of a single parameter -- the ratio between the random medium's and the beam's transverse correlation lengths, even in the regime of pronounced intensity fluctuations.

physics.optics↗

arXiv2022

Highly-transmitting modes of light in dynamic atmospheric turbulence

We show that instantaneous spatial singular modes of light in a dynamically evolving, turbulent atmosphere offer significantly improved high-fidelity signal transmission as compared to standard encoding bases corrected by adaptive optics. Their enhanced stability in stronger turbulence is associated with a subdiffusive algebraic decay of the transmitted power with evolution time.

physics.optics↗

arXiv2019

Universal entanglement decay of photonic orbital angular momentum qubit states in atmospheric turbulence: an analytical treatment

We study the entanglement evolution of photonic orbital angular momentum qubit states with opposite azimuthal indices $l_0$, in a weakly turbulent atmosphere. Using asymptotic methods, we deduce analytical expressions for the amplitude of turbulence-induced crosstalk between the modes $l_0$ and $-l_0$. Furthermore, we analytically establish distinct, universal entanglement decay laws for Kolmogorov's turbulence model and for two approximations thereof.

quant-ph↗