arXiv subjects

Daniel Younis

Publications and source records attributed to Daniel Younis.

4 recordsLinked to original sources

arXiv2024

Quantum entanglement during single-cycle nonsequential ionization

In order to elucidate the correlated motion of atomic electrons, we investigate the attosecond-scale dynamics of their entanglement arising due to nonsequential ionization driven by a strong, linearly-polarized laser field. The calculation is based on numerical integration of the time-dependent Schr\"{o}dinger equation for helium irradiated by a one-cycle, near-infrared field whose intensity is in the neighborhood of $1\textrm{ PW/cm}^2$. The entanglement measure (Schmidt weight) is resolved on a sub-cycle timescale, and its key dependency on the field profile is exposed for the first time by tuning the carrier-envelope phase (CEP) to control the ionization-recollision timing. We find that between CEP cases, this can result in a $20\%$ enhancement in the peak entanglement. A connection is made between the entanglement, the probability current, and the correlation coefficient for the two electron momenta, providing new insights into the nonsequential ionization mechanism.

physics.atom-ph↗

arXiv2023

Unexpected Robustness of Multipartite Entanglement against Sudden Death from Spontaneous Emission

Entanglement is known to decay even in isolated systems, an effect attributed to spontaneous emission. This fragility of entanglement can be exacerbated by entanglement sudden death (ESD), where entanglement drops to zero abruptly within a finite time. It is natural to assume that multipartite entanglement is more vulnerable to ESD, as it involves more parties experiencing spontaneous emission. In this work, we challenge this assumption and present a contrasting conclusion, asserting that multipartite entanglement demonstrates increased robustness against ESD from spontaneous emission.

quant-ph↗

arXiv2023

Multipartite Entanglement: A Journey Through Geometry

Genuine multipartite entanglement is crucial for quantum information and related technologies but quantifying it has been a long-standing challenge. Most proposed measures do not meet the ``genuine'' requirement, making them unsuitable for many applications. In this work, we propose a journey toward addressing this issue by introducing an unexpected relation between multipartite entanglement and hypervolume of geometric simplices, leading to a tetrahedron measure of quadripartite entanglement. By comparing the entanglement ranking of two highly entangled four-qubit states, we show that the tetrahedron measure relies on the degree of permutation invariance among parties within the quantum system. We demonstrate potential future applications of our measure in the context of quantum information scrambling within many-body systems.

quant-ph↗

arXiv2023

Strong-Field Nonsequential Double Photoionization Using Virtual Detector Theory with Path Summation

We present an ab initio study of the nonsequential strong-field ionization dynamics of a model two-electron atom with helium character. Single- and double-ionization events are characterized and displayed using detector signals extracted at different points in the two-electron two-dimensional space. The double photoelectron momentum distribution is calculated via coherent path-summation over virtual particle trajectories. Insights into different ionization and electron recollision pathways are gained from detailed virtual-particle tracking and energy-time readouts. This study demonstrates the extension of virtual detector theory to strong-field multi-electron quantum dynamics and highlights the importance of the evolving quantum phase in quasi-classical electron propagation.

physics.atom-ph↗