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Andrew Ivanov

Publications and source records attributed to Andrew Ivanov.

7 recordsLinked to original sources
arXiv2023

Bloch Oscillation Phases investigated by Multi-path Stuckelberg Atom Interferometry

Atoms undergoing Bloch oscillations (BOs) in an accelerating optical lattice acquire momentum of two photon recoils per BO. This technique provides a large momentum transfer tool for atom optics, but its full exploitation for atom interferometric sensors requires experimental characterization of associated phases. Each BO involves a Landau-Zener crossing with multiple crossings inducing interference known as Stuckelberg interference. We develop a multi-path Stuckelberg interferometer and investigate atomic phase evolution during BOs, up to 100 photon recoil momentum transfer. We compare to numerically calculated single-particle Schrodinger evolution, demonstrate highly coherent BO sequences, and assess phase stability requirements for BO-enhanced precision interferometry in fundamental physics and sensing applications.

physics.atom-ph↗
arXiv2022

Learning the shape of protein micro-environments with a holographic convolutional neural network

Proteins play a central role in biology from immune recognition to brain activity. While major advances in machine learning have improved our ability to predict protein structure from sequence, determining protein function from structure remains a major challenge. Here, we introduce Holographic Convolutional Neural Network (H-CNN) for proteins, which is a physically motivated machine learning approach to model amino acid preferences in protein structures. H-CNN reflects physical interactions in a protein structure and recapitulates the functional information stored in evolutionary data. H-CNN accurately predicts the impact of mutations on protein function, including stability and binding of protein complexes. Our interpretable computational model for protein structure-function maps could guide design of novel proteins with desired function.

physics.bio-ph↗
arXiv2021

Impact of surface and laser-induced noise on the spectral stability of implanted nitrogen-vacancy centers in diamond

Scalable realizations of quantum network technologies utilizing the nitrogen vacancy center in diamond require creation of optically coherent NV centers in close proximity to a surface for coupling to optical structures. We create single NV centers by $^{15}$N ion implantation and high-temperature vacuum annealing. Origin of the NV centers is established by optically detected magnetic resonance spectroscopy for nitrogen isotope identification. Near lifetime-limited optical linewidths ($<$ 60 MHz) are observed for the majority of the normal-implant (7$^\circ$, $\approx$ 100 nm deep) $^{15}$NV centers. Long-term stability of the NV$^-$ charge state and emission frequency is demonstrated. The effect of NV-surface interaction is investigated by varying the implantation angle for a fixed ion-energy, and thus lattice damage profile. In contrast to the normal implant condition, NVs from an oblique-implant (85$^\circ$, $\approx$ 20 nm deep) exhibit substantially reduced optical coherence. Our results imply that the surface is a larger source of perturbation than implantation damage for shallow implanted NVs. This work supports the viability of ion implantation for formation of optically stable NV centers. However, careful surface preparation will be necessary for scalable defect engineering.

cond-mat.mes-hall↗
arXiv2020

Inverse-designed photon extractors for optically addressable defect qubits

Solid-state defect qubit systems with spin-photon interfaces show great promise for quantum information and metrology applications. Photon collection efficiency, however, presents a major challenge for defect qubits in high refractive index host materials. Inverse-design optimization of photonic devices enables unprecedented flexibility in tailoring critical parameters of a spin-photon interface including spectral response, photon polarization and collection mode. Further, the design process can incorporate additional constraints, such as fabrication tolerance and material processing limitations. Here we design and demonstrate a compact hybrid gallium phosphide on diamond inverse-design planar dielectric structure coupled to single near-surface nitrogen-vacancy centers formed by implantation and annealing. We observe device operation near the theoretical limit and measure up to a 14-fold broadband enhancement in photon extraction efficiency. We expect that such inverse-designed devices will enable realization of scalable arrays of single-photon emitters, rapid characterization of new quantum emitters, sensing and efficient heralded entanglement schemes.

physics.app-ph↗
arXiv2019

A window into NV center kinetics via repeated annealing and spatial tracking of thousands of individual NV centers

Knowledge of the nitrogen-vacancy center formation kinetics in diamond is critical to engineering sensors and quantum information devices based on this defect. Here we utilize the longitudinal tracking of single NV centers to elucidate NV defect kinetics during high-temperature annealing from 800-1100 $^\circ$C in high-purity chemical-vapor-deposition diamond. We observe three phenomena which can coexist: NV formation, NV quenching, and NV orientation changes. Of relevance to NV-based applications, a 6 to 24-fold enhancement in the NV density, in the absence of sample irradiation, is observed by annealing at 980 $^\circ$C, and NV orientation changes are observed at 1050 $^\circ$C. With respect to the fundamental understanding of defect kinetics in ultra-pure diamond, our results indicate a significant vacancy source can be activated for NV creation between 950-980 $^\circ$C and suggests that native hydrogen from NVH$_y$ complexes plays a dominant role in NV quenching, in agreement with recent {\it ab initio} calculations. Finally, the direct observation of orientation changes allows us to estimate an NV diffusion barrier of 5.1~eV.

cond-mat.mtrl-sci↗