Posts by Collection

Demonstration of 3D Effects with High Gain and Efficiency in a UV FEL Oscillator

Published in 2011 Particle Accelerator Conference, 2011

We report on the performance of a high gain UV FEL oscillator operating on an energy recovery linac at Jefferson Lab and find 3D simulations do predict the performance with reasonable precision.

Benson, S., Biallas, G., Blackburn, K., [et. al., including Watson, A.], (2011). "Demonstration of 3D Effects with High Gain and Efficiency in a UV FEL Oscillator." In 2011 Particle Accelerator Conference (pp. 2429-2431).

A New Approach to Improving the Efficiency of FEL Oscillator Simulations

Published in 34th International Free Electron Laser Conference, 2012

We compare 2D, 3D, and 4D free-electron laser (FEL) oscillator simulation codes against the measured performances of three oscillator FELs.

Shinn, M.D., Benson, S.V.,Watson, A.M., van der Slot, P.J., Freund, H.P. and Nguyen, D.C. (2012). "A new approach to improving the efficiency of fel oscillator simulations." In 34th International Free-Electron Laser Conference (pp. 225-228).

JLIFE: The Jefferson Lab Interactive Front End For The Optical Propagation Code

Published in 35th International Free Electron Laser Conference, 2013

We present the design and construction of a graphical interface for the open source software program Optical Propagation Code (OPC) to model wave propagation in FEL oscillators.

Watson, A.M., Shinn, M.D. (2013). "JLIFE: The Jefferson Lab Interactive Front End For The Optical Propagation Code." In 35th International Free-Electron Laser Conference. (pp. 149-151).

Surface-enhanced Raman scattering plasmonic enhancement using DNA origami-based complex metallic nanostructures

Published in Nano Letters, 2014

We use DNA origami templates to engineer surface-enhanced Raman scattering substrates and show a significant Raman signal enhancement from molecules covalently attached to the assemblies.

Pilo-Pais, M., Watson, A., Demers, S., LaBean, T.H., Finkelstein, G. (2014). "Surface-enhanced Raman scattering plasmonic enhancement using DNA origami-based complex metallic nanostructures." Nano Lett. 14(4), pp.2099-2104.

Topographic measurement of buried thin-film interfaces using a grazing resonant soft x-ray scattering technique

Published in Physical Review B, 2014

We demonstrate that grazing resonant soft x-ray scattering (GRSoXS), a technique measuring diffusely scattered soft x rays from grazing incidence, can reveal the statistical topography of buried thin-film interfaces.

Gann, E., Watson, A., Tumbleston, J.R., Cochran, J., Yan, H., Wang, C., Seok, J., Chabinyc, M., Ade, H. (2014). "Topographic measurement of buried thin-film interfaces using a grazing resonant soft x-ray scattering technique." Phys. Rev. B 90(24), p. 245421.

Rhodium Nanoparticles for Ultraviolet Plasmonics

Published in Nano Letters, 2015

We present for the first time the use of rhodium nanoparticles for ultraviolet plasmonics, demonstrating essential steps toward plasmonically enhanced ultraviolet photocatalysis.

Watson, A.M., Zhang, X., Alcaraz de La Osa, R., Sanz, J.M., González, F., Moreno, F., Finkelstein, G., Liu, J., Everitt, H.O. (2015). "Rhodium nanoparticles for ultraviolet plasmonics." Nano Lett. 15(2), pp.1095-1100.

Plasmonics in the UV range with Rhodium nanocubes

Published in Proceedings of SPIE 9884, 2016

We study the electromagnetic behaviour of isolated Rh nanocubes of different sizes through numerical simulations and compare with experimental measurements.

Zhang, X., Gutiérrez, Y., Li, P., Barreda, Á.I., Watson, A.M., de la Osa, R.A., Finkelstein, G., González, F., Ortiz, D., Saiz, J.M., Sanz, J.M. (2016). "Plasmonics in the UV range with Rhodium nanocubes." In Nanophotonics VI (Vol. 9884, p. 98841E), International Society for Optics and Photonics.

Critical current scaling in long diffusive graphene-based Josephson junctions

Published in Nano Letters, 2016

We present low-temperature transport measurements on long, diffusive, graphene-based Josephson junctions and examine the relationship between critical current and the Thouless energy for different junction lengths.

Ke, C.T., Borzenets, I.V., Draelos, A.W., Amet, F., Bomze, Y., Jones, G., Craciun, M., Russo, S., Yamamoto, M., Tarucha, S., Finkelstein, G. (2016). "Critical current scaling in long diffusive graphene-based Josephson junctions." Nano Lett. 16(8), pp. 4788-4791.

Ballistic graphene Josephson junctions from the short to the long junction regimes

Published in Physical Review Letters, 2016

We present low-temperature transport measurements on ballistic graphene-based Josephson junctions and find a crossover from the short to the long junction regimes as the length of the device increases.

Borzenets, I.V., Amet, F., Ke, C.T., Draelos, A.W., Wei, M.T., Seredinski, A., Watanabe, K., Taniguchi, T., Bomze, Y., Yamamoto, M., Tarucha, S., and Finkelstein, G. (2016). "Ballistic graphene Josephson junctions from the short to the long junction regimes." Phys. Rev. Lett. 117(23), p. 237002.

Investigation of Supercurrent in the Quantum Hall Regime in Graphene Josephson Junctions

Published in Journal of Low Temperature Physics, 2018

We examine multiple encapsulated graphene Josephson junctions to determine which mechanisms may be responsible for supercurrent observed in the quantum Hall regime.

Draelos, A.W., Wei, M.T., Seredinski, A., Ke, C.T., Mehta, Y., Chamberlain, R., Watanabe, K., Taniguchi, T., Yamamoto, M., Tarucha, S., Borzenets, I.V., Amet, F., Finkelstein, G. (2018). "Investigation of supercurrent in the quantum Hall regime in graphene Josephson junctions." J. Low Temp. Phys. 191(5-6), pp. 288-300.

Supercurrent in Graphene Josephson Junctions with Narrow Trenches in the Quantum Hall Regime

Published in MRS Advances, 2018

We report on low-temperature transport measurements in devices constructed with a narrow trench perpendicular to the contacts in a Josephson junction, which create counterpropagating quantum Hall edge channels tens of nanometres from each other.

Seredinski, A., Draelos, A., Wei, M.T., et. al. (2018). "Supercurrent in Graphene Josephson Junctions with Narrow Trenches in the Quantum Hall Regime." MRS Advances 3(47-48), pp. 2855-2864.

Supercurrent flow in multiterminal graphene Josephson junctions

Published in Nano Letters, 2019

We present the first investigation of the electronic properties of ballistic planar Josephson junctions with multiple superconducting terminals and find that superconducting and dissipative currents coexist within the same region of graphene.

Draelos, A.W., Wei, M.T., Seredinski, A., Li, H., Mehta, Y., Watanabe, K., Taniguchi, T., Borzenets, I.V., Amet, F., Finkelstein, G. (2019). "Supercurrent flow in multiterminal graphene Josephson junctions." Nano Lett. 19(2), pp. 1039-1043.

Subkelvin lateral thermal transport in diffusive graphene

Published in Physical Review B, 2019

We report on hot carrier diffusion in graphene across large enough length scales that the carriers are not thermalized across the crystal at low temperatures and thus observe a thermal gradient.

Draelos, A.W., Silverman, A., Eniwaye, B., Arnault, E.G., Ke, C.T., Wei, M.T., Vlassiouk, I., Borzenets, I.V., Amet, F., Finkelstein, G. (2019). "Subkelvin lateral thermal transport in diffusive graphene." Phys. Rev. B 99(12), p. 125427.

Chiral quasiparticle tunneling between quantum Hall edges in proximity with a superconductor

Published in Physical Review B, 2019

We study a two-terminal graphene Josephson junction with contacts shaped to form a narrow 100 nm constriction and observe enhanced conductance through a wide range of magnetic fields and gate voltages.

Wei, M.T., Draelos, A.W., Seredinski, A., Ke, C.T., Li, H., Mehta, Y., Watanabe, K., Taniguchi, T., Yamamoto, M., Tarucha, S., Finkelstein, G., Amet., F., Borzenets, I.V. (2019). "Chiral quasiparticle tunneling between quantum Hall edges in proximity with a superconductor." Phys. Rev. B 100(12), p. 121403.

Quantum Hall–based superconducting interference device

Published in Science Advances, 2019

We present a study of a graphene-based Josephson junction in the quantum Hall regime with dedicated side gates carved from the same sheet of graphene as the junction itself and observe a supercurrent localized along that edge of the junction.

Seredinski, A., Draelos, A.W., Arnault, E., Wei, M.T., Li, H., Fleming, T., Watanabe, K., Taniguchi, T., Amet, F., Finkelstein, G. (2019). "Quantum Hall–based superconducting interference device." Sci. Adv. 5(9), eaaw8693.

Anomalous periodicity of magnetic interference patterns in encapsulated graphene Josephson junctions

Published in Physical Review Research, 2019

We investigate supercurrent interference patterns measured as a function of magnetic field in ballistic graphene Josephson junctions and find anomalous interferences that are close to the periodicity predicted for topological Andreev bound states carrying a charge of e, not 2e.

Ke, C.T., Draelos, A.W., Seredinski, A., et. al. (2019). "Anomalous periodicity of magnetic interference patterns in encapsulated graphene Josephson junctions." Phys. Rev. Research 1(3), p. 033084.

Interference of chiral Andreev edge states

Published in Nature Physics, 2020

We explore the interface between a quantum Hall insulator and an s-wave superconductor in graphene Josephson junctions and find clear signatures of hybridized electron and hole states similar to chiral Majorana fermions, called chiral Andreev edge states.

Zhao, L., Arnault, E.G., Bondarev, A., Seredinski, A., Larson, T.F., Draelos, A.W., Li, H., Watanabe, K., Taniguchi, T., Amet, F., Baranger, H.U., Finkelstein, G. (2020). "Interference of chiral Andreev edge states." Nat. Phys., pp. 1-6.

Online Neural Connectivity Estimation with Noisy Group Testing

Published in Advances in Neural Information Processing Systems (NeurIPS), 2020

We describe a method based on noisy group testing to infer functional connections in large networks of neurons. By stimulating small ensembles of neurons, we show that it is possible to recover binarized network connectivity with a number of tests that grows only logarithmically with population size under minimal statistical assumptions. We extend our method to the streaming setting, where continuously updated posteriors allow for optional stopping, and demonstrate the feasibility of inferring connectivity for networks of up to tens of thousands of neurons online.

Draelos, A., Pearson, J. M. (2020). "Online Neural Connectivity Estimation with Noisy Group Testing." Advances in Neural Information Processing Systems 33.'

https://proceedings.neurips.cc/paper/2020/file/531d29a813ef9471aad0a5558d449a73-Paper.pdf

improv: A flexible software platform for adaptive neuroscience experiments

Published in bioRxiv (preprint), 2021

We introduce improv, a software platform that allows users to flexibly specify and manage adaptive experiments to integrate data collection, preprocessing, visualization, and user-defined analytics. Using improv for streaming data analysis for two-photon calcium imaging and behavior, we demonstrate how access to online information can be used for automated, integrated experimentation.

Draelos, A., Nikitchenko, M., Sriworarat, C., Sprague, D., Loring, M. D., Pnevmatikakis, E., Giovannucci, A., Naumann, E. A., and Pearson, J. M. (2021). "improv: A flexible software platform for adaptive neuroscience experiments." bioRxiv:10.1101/2021.02.22.432006

https://www.biorxiv.org/content/10.1101/2021.02.22.432006v1.full.pdf

Bubblewrap: Online tiling and real-time flow prediction on neural manifolds

Published in Advances in Neural Information Processing Systems 34, 2021

We present a method that combines fast, stable dimensionality reduction with a soft tiling of the resulting neural manifold, allowing dynamics to be approximated as a probability flow between tiles. This method can be fit efficiently using online expectation maximization, scales to tens of thousands of tiles, and outperforms existing methods when dynamics are noise-dominated or feature multi-modal transition probabilities. The resulting model can be trained at kiloHertz data rates, produces accurate approximations of neural dynamics within minutes, and generates predictions on submillisecond time scales. It retains predictive performance throughout many time steps into the future and is fast enough to serve as a component of closed-loop causal experiments.

Draelos, A., Gupta, P., Jun, N. Y., Sriworarat, C., and Pearson, J. (2021). "Bubblewrap: Online tiling and real-time flow prediction on neural manifolds." Advances in Neural Information Processing Systems 34 (accepted; also at arXiv:2108.13941)

https://arxiv.org/pdf/2108.13941.pdf

Bubblewrap: Online tiling and real-time flow prediction on neural manifolds

We developed a new method for approximating dynamics as a probability flow between discrete tiles on a low-dimensional manifold. The model can be trained quickly and retains predictive performance many time steps into the future, and is fast enough to serve as a component of closed-loop causal experiments in neuroscience. Our recent preprint on this work can be found here.

Online neural connectivity estimation with noisy group testing

How can we get connectivity between large systems of neurons in vivo? Using stimulations of small ensembles and a statistical method called group testing, we show in our recent paper that this is now feasible even in networks of up to 10 thousand neurons.

improv: real-time analysis and adaptive experimental designs

A software platform for construction and orchestration of adaptive experiments, improv has been used to analyze streaming two-photon calcium images in larval zebrafish in real time and to fit GLM models to infer weighted connections among neurons as the experiment is ongoing. The codebase is open-source and freely available at github.com/pearsonlab/improv, and the associated paper can be found here.

Graduate Research

Interplay of supercurrent in multiterminal devices

First observation of complex supercurrent flow in a four-terminal graphene Josephson junction, where we find an unusual coexistence of supercurrent and dissipative currents in the same location. The paper can be found here.

Superconductivity and the quantum Hall effect

Research into the mechanisms of superconducting currents in the quantum Hall regime in two-dimensional graphene Josephson junctions. Selected papers can be found here, here, here, and here.

Adaptive platform for online characterization of neural data

Published: October 21, 2019

Adaptive platform for online characterization of neural data

Published: October 31, 2019

Adaptive platform for online characterization of neural data

Published: November 12, 2019

Adaptive causal inference: identifying and manipulating neural function in real time

Published: March 01, 2020

I discussed the need for adaptive experimental designs to leverage high-throughput neural data and novel interventional tools such as holographic photostimulation and presented new methods for practical streaming analysis and algorithms for automatically dissecting neural circuits.

Real-time analysis and stimulation of neuronal populations

Published: August 11, 2020

As part of the Leading Edge Symposium series of talks, I presented on our work on adaptive experimental designs and inferring functional connections in large populations of neurons.

A flexible real-time platform for adaptive neuroscience experiments

Published: October 22, 2020

My talk on our software platform, improv, won the Best Poster award. I showcased the various applications for adaptive experimental designs and how real-time analyses can drastically speed-up discovery in neuroscience.

Mapping the dynamic brain

Published: January 26, 2021

I was selected for a postdoc research talk showcase during the 2021 Duke Research Week. I presented our recent work on how to conduct causal experiments in neuroscience at scale, from small circuits to entire brains.

Real-time neural modeling for adaptive neuroscience experiments

Published: May 07, 2021

I discussed our work on adaptive designs to enable real-time, interventional experiments in neuroscience. In particular, I highlighted our recent paper on estimating functional connectivity through ensemble stimulations and discussed our adaptive software platform to make such experiments a reality.

Real-time analysis of neural activity and functional connectivity

Published: June 16, 2021

I was selected for a trainee highlight award talk at the 2021 BRAIN Initiative investigators meeting. I presented our recent work on adaptive group photostimulation and visual stimlus optimization.

PHY264L: Optics & Modern Physics lab

Undergraduate lab course, Duke University, Physics Dept., 2012

Teaching assistant for the Optics and Modern Physics lab course. I updated and expanded computational and documentation portions of the lab, as well as assisted students with standard and custom experimental modules.

PHY363: Thermal Physics

Undergraduate physics major course, Duke University, Physics Dept., 2014

Teaching assistant for the Thermal Physics course for physics majors. I gave some lectures, held office hours, and graded homeworks and exams. I additionally developed problem set solutions and grading rubrics.