Papers by Georgios Stratis
Physical review. A/Physical review, A, Feb 20, 2024
arXiv (Cornell University), Sep 4, 2023
Bulletin of the American Physical Society, Jun 7, 2013
We demonstrate sub-Doppler laser cooling and magneto-optical trapping of the rare earth element H... more We demonstrate sub-Doppler laser cooling and magneto-optical trapping of the rare earth element Holmium. Atoms are loaded from an atomic beam source and captured in six-beam σ+−σ− molasses using a strong J = 15/2 ↔ J = 17/2 cycling transition at λ = 410.5 nm. Due to the small difference in hyperfine splittings and Landé g-factors in the lower and upper levels of the cooling transition the MOT is self-repumped without additional repump light, and deep sub-Doppler cooling is achieved with the magnetic trap turned on. We measure the leakage out of the cycling transition to metastable states and find a branching ratio < 10 −5 which is adequate for state resolved measurements on hyperfine encoded qubits.
Physical review, Nov 8, 2022
Quantum Monte-Carlo simulations of hybrid quantum-classical models such as the double exchange Ha... more Quantum Monte-Carlo simulations of hybrid quantum-classical models such as the double exchange Hamiltonian require calculating the density of states of the quantum degrees of freedom at every step. Unfortunately, the computational complexity of exact diagonalization grows O(N 3) as a function of the system's size N , making it prohibitively expensive for any realistic system. We consider leveraging data-driven methods, namely neural networks, to replace the exact diagonalization step in order to speed up sample generation. We explore a model that learns the free energy for each spin configuration and a second one that learns the Hamiltonian's eigenvalues. We implement data augmentation by taking advantage of the Hamiltonian's symmetries to artificially enlarge our training set and benchmark the different models by evaluating several thermodynamic quantities. While all models considered here perform exceedingly well in the one-dimensional case, only the neural network that outputs the eigenvalues is able to capture the right behavior in two dimensions. The simplicity of the architecture we use in conjunction with the model agnostic form of the neural networks can enable fast sample generation without the need of a researcher's intervention.
Journal of Chemical Physics, Jan 21, 2021
Physica Scripta, Oct 31, 2018
Well-collimated, high-intensity beams of neutral atoms have many applications ranging from atom m... more Well-collimated, high-intensity beams of neutral atoms have many applications ranging from atom microscopy to atom interferometry to ultracold atomic physics. We experimentally demonstrate a method for brightening a supersonic atomic beam and observe an increase in the phase space density by a factor of at least 20. Our scheme relies upon a permanent magnetic hexapole lens to focus a divergent beam of neutral atoms emitted from a supersonic nozzle and transverse laser cooling as the beam converges downstream from the lens so as to create a dense, narrow, Doppler-collimated atomic beam. In principle, this method can be repeated multiple times in series for further beam brightening.
The Journal of Chemical Physics
The breaking of molecular bonds during exposure to ionizing radiation and electron beams creates ... more The breaking of molecular bonds during exposure to ionizing radiation and electron beams creates irreversible damage in the molecular structure. In some cases, such as lithography, controlled damage of a molecular resist is a desirable process and is the basis for the entire semiconductor industry. In other cases, such as environmental exposure or probing of the molecular structure, the induced damage is a major problem that has limited advances in science and technology. We report here the use of an in situ probe that is minimally invasive to detect real-time damage induced in organic materials. Specifically, we use metastable excited helium atoms in the 3S1 state to characterize the damage caused by a low-energy electron beam ∼30 eV on an organic self-assembled monolayer of 11-bromo-1-undecanethiol on a gold substrate. We were able to monitor the damage caused by the electron beam without introducing any additional observed damage by the probing metastable atoms.
Physica Scripta, 2018
Well-collimated, high-intensity beams of neutral atoms have many applications ranging from atom m... more Well-collimated, high-intensity beams of neutral atoms have many applications ranging from atom microscopy to atom interferometry to ultracold atomic physics. We experimentally demonstrate a method for brightening a supersonic atomic beam and observe an increase in the phase space density by a factor of at least 20. Our scheme relies upon a permanent magnetic hexapole lens to focus a divergent beam of neutral atoms emitted from a supersonic nozzle and transverse laser cooling as the beam converges downstream from the lens so as to create a dense, narrow, Doppler-collimated atomic beam. In principle, this method can be repeated multiple times in series for further beam brightening.
Bulletin of the American Physical Society, Mar 5, 2015
Physical Review A, 2014
We demonstrate sub-Doppler laser cooling and magneto-optical trapping of the rare earth element H... more We demonstrate sub-Doppler laser cooling and magneto-optical trapping of the rare earth element Holmium. Atoms are loaded from an atomic beam source and captured in six-beam σ+−σ− molasses using a strong J = 15/2 ↔ J = 17/2 cycling transition at λ = 410.5 nm. Due to the small difference in hyperfine splittings and Landé g-factors in the lower and upper levels of the cooling transition the MOT is self-repumped without additional repump light, and deep sub-Doppler cooling is achieved with the magnetic trap turned on. We measure the leakage out of the cycling transition to metastable states and find a branching ratio < 10 −5 which is adequate for state resolved measurements on hyperfine encoded qubits.
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Papers by Georgios Stratis