Showing 1–14 of 14 results for author: Davis, W

Sample-based Quantum Diagonalization Methods for Modeling the Photochemistry of Diazirine and Diazo Compounds

Authors: Saurabh Shivpuje, Tanvi P. Gujarati, Richard Van, Frank C. Pickard IV, Triet Friedhoff, Ieva Liepuoniute, Wade Davis, Gavin O. Jones, Alexey Galda

Abstract: Diazirines and diazo compounds are widely employed as photoreactive precursors for generating carbenes, key intermediates in chemical biology and materials science. However, computationally modeling their reaction pathways remains challenging due to a need for large active spaces and the requirement to accurately capture excited-state surfaces along with transition states and conical intersections… ▽ More Diazirines and diazo compounds are widely employed as photoreactive precursors for generating carbenes, key intermediates in chemical biology and materials science. However, computationally modeling their reaction pathways remains challenging due to a need for large active spaces and the requirement to accurately capture excited-state surfaces along with transition states and conical intersections. In this work, we utilize a hybrid quantum-classical workflow for investigating carbene formation in representative diazirine-diazomethane systems. Our approach leverages Sample-based Quantum Diagonalization (SQD) and its extended variant (Ext-SQD) for ground and excited-state analysis, combined with classical tools for geometry optimization, active-space selection, and diagnostic evaluation. Quantum computations were carried out on superconducting quantum processors, and results for both aliphatic and aryl-substituted diazirine-diazomethane pairs were benchmarked against established classical methods, including DFT, CCSD, CASCI, and SCI. SQD achieves accuracy surpassing the chemical accuracy threshold for nearly all stationary points on the potential energy surface of parent diazirine relative to the CASCI(12,10) reference, and remains close to chemical accuracy for phenyl-substituted diazirine in a (30,30) active space, with an average deviation of 1.1 kcal/mol relative to the SCI benchmark. SQD closely follows CASCI and SCI trends, showing consistent agreement. The findings demonstrate the promise of quantum computing frameworks in modeling photochemical transformations of electronically complex and pharmacologically relevant molecules. △ Less

Submitted 1 October, 2025; originally announced October 2025.

Comments: 15 pages, 3 figures, 2 tables, supplementary information

Cavity-based optical switching via phase modulation in warm rubidium vapor

Authors: Georgia Booton, Tabijah Wasawo, William O. C. Davis, Cameron McGarry, Kristina R. Rusimova, Alex O. C. Davis, Josh Nunn, Peter J. Mosley

Abstract: Optical switching remains a key outstanding challenge for scalable fault-tolerant photonic quantum computing due to the trade-off between speed, bandwidth, and loss. Scalable quantum photonics demands all three, to enable high computational clock rates and resource efficient scaling to large systems. We present a cavity-based optical switch that overcomes this limitation, demonstrating 22 ns rise… ▽ More Optical switching remains a key outstanding challenge for scalable fault-tolerant photonic quantum computing due to the trade-off between speed, bandwidth, and loss. Scalable quantum photonics demands all three, to enable high computational clock rates and resource efficient scaling to large systems. We present a cavity-based optical switch that overcomes this limitation, demonstrating 22 ns rise time, insertion loss of 2.4 dB, and 17.5 dB extinction ratio. All-optical control is achieved via phase modulation of a signal field detuned from the near-degenerate two-photon absorption ladder in warm rubidium vapor. The ultimate performance of our switch, combining both speed and efficiency, will find applications in active multiplexing, loop-based quantum memory, and feedforward for quantum error-correction protocols. △ Less

Submitted 11 August, 2025; v1 submitted 8 August, 2025; originally announced August 2025.

Background in Low Earth Orbiting Cherenkov Detectors, and Mitigation Strategies

Authors: Christopher S. W. Davis, Fan Lei, Keith Ryden, Clive Dyer, Giovanni Santin, Piers Jiggens, Melanie Heil

Abstract: Cherenkov detectors have been used in space missions for many decades, and for a variety of purposes, including for example, for Galactic Cosmic Ray (GCR) and Solar Energetic Particle (SEP) measurements. Cherenkov detectors are sensitive to many types of particles that are present in the environment of space, including gamma rays, trapped particles and cosmic particles, and each particle component… ▽ More Cherenkov detectors have been used in space missions for many decades, and for a variety of purposes, including for example, for Galactic Cosmic Ray (GCR) and Solar Energetic Particle (SEP) measurements. Cherenkov detectors are sensitive to many types of particles that are present in the environment of space, including gamma rays, trapped particles and cosmic particles, and each particle component acts as essentially a background when trying to view another specific particle component. In this research, GRAS/Geant4 simulations were performed to characterise the count rates that a simple Cherenkov detector design would experience in a low Earth orbit, and we find that Cherenkov count rates due to most particle components vary significantly depending on many different factors, including the location in the orbit, the date of the orbit, whether or not the detector is within the van Allen belts, and whether or not a solar particle event is occurring. We find that a small Cherenkov detector is readily able to gather detailed data on both trapped particles and spectral information during Ground-Level Enhancements. We also investigate the use of coincidence as a method to remove count rates due to trapped particles and delta electrons, finding that this method is generally very effective for resolving count rates due to GLEs amongst intense trapped particle environments, but that some Cherenkov count rates due to trapped particles are still observed in the simulated south Atlantic anomaly region. △ Less

Submitted 4 July, 2025; originally announced July 2025.

Comments: 35 pages, 9 figures, 3 tables. Submitted to Nuclear Inst. and Methods in Physics Research, A

Journal ref: Journal of Geophysical Research: Space Physics (2026)

AniMAIRE -- A New Openly Available Tool for Calculating Atmospheric Ionising Radiation Dose Rates and Single Event Effects During Anisotropic Conditions

Authors: Christopher Stephen William Davis, Fraser Baird, Fan Lei, Keith Ryden, Clive Dyer

Abstract: AniMAIRE (Anisotropic Model for Atmospheric Ionising Radiation Effects) is a new model and Python toolkit for calculating radiation dose rates experienced by aircraft during anisotropic solar energetic particle events. AniMAIRE expands the physics of the MAIRE+ model such that dose rate calculations can be performed for anisotropic solar energetic particle conditions by supplying a proton or alpha… ▽ More AniMAIRE (Anisotropic Model for Atmospheric Ionising Radiation Effects) is a new model and Python toolkit for calculating radiation dose rates experienced by aircraft during anisotropic solar energetic particle events. AniMAIRE expands the physics of the MAIRE+ model such that dose rate calculations can be performed for anisotropic solar energetic particle conditions by supplying a proton or alpha particle rigidity spectrum, a pitch angle distribution, and the conditions of Earth's magnetosphere. In this paper, we describe the algorithm and top-level structure of AniMAIRE and showcase AniMAIRE's capabilities by analysing the dose rate maps that AniMAIRE produces when the time-dependent spectra and pitch angle distribution for GLE71 are inputted. We find that the dose rates AniMAIRE produces for the event fall between the dose rates produced by the WASAVIES and CRAC:DOMO models. Dose rate maps that evolve throughout the event are also shown, and it is found that each peak in the inputted pitch angle distribution generates a dose rate hotspot in each of the polar regions. AniMAIRE has been made available openly online so that it can be downloaded and run freely on local machines and so that the space weather community can easily contribute to it using Github forking. △ Less

Submitted 8 May, 2024; v1 submitted 6 May, 2024; originally announced May 2024.

Comments: 22 pages, 7 figures, manuscript submitted to Space Weather Journal. The previous version of this had the incorrect abstract and title, this has been fixed in this version

Journal ref: Space Weather, 22, e2024SW003985

Fast, low-loss all-optical phase modulation in warm rubidium vapour

Authors: William Davis, Paul Burdekin, Tabijah Wasawo, Sarah E Thomas, Peter J Mosley, Joshua Nunn, Cameron McGarry

Abstract: Low-loss high-speed switches are an integral component of future photonic quantum technologies, with applications in state generation, multiplexing, and the implementation of quantum gates. Phase modulation is one method of achieving this switching, but existing optical phase modulators either achieve high bandwidth or low loss, but not both. We demonstrate fast ($100\,\mathrm{MHz}$ bandwidth), lo… ▽ More Low-loss high-speed switches are an integral component of future photonic quantum technologies, with applications in state generation, multiplexing, and the implementation of quantum gates. Phase modulation is one method of achieving this switching, but existing optical phase modulators either achieve high bandwidth or low loss, but not both. We demonstrate fast ($100\,\mathrm{MHz}$ bandwidth), low-loss ($83\pm2\%$ transmission) phase shifting ($Δφ= (0.90\pm0.05)π$) in a signal field, induced by a control field, and mediated by the two-photon $5S_{1/2} \rightarrow{} 5P_{3/2} \rightarrow{} 5D_{5/2}$ transition in $^{87}\text{Rb}$ vapour. We discuss routes to enhance both performance and scalability for application to a range of quantum and classical technologies. △ Less

Submitted 25 August, 2024; v1 submitted 8 September, 2023; originally announced September 2023.

Comments: 10 pages, 6 figures, this version includes more detailed simulation with collaborators from Imperial College London

Reconstruction of Stochastic Dynamics from Large Streamed Datasets

Authors: William Davis

Abstract: The complex dynamics of physical systems can often be modeled with stochastic differential equations. However, computational constraints inhibit the estimation of dynamics from large time-series datasets. I present a method for estimating drift and diffusion functions from inordinately large datasets through the use of incremental, online, updating statistics. I demonstrate the validity and utilit… ▽ More The complex dynamics of physical systems can often be modeled with stochastic differential equations. However, computational constraints inhibit the estimation of dynamics from large time-series datasets. I present a method for estimating drift and diffusion functions from inordinately large datasets through the use of incremental, online, updating statistics. I demonstrate the validity and utility of this method by analyzing three large, varied synthetic datasets, as well as an empirical turbulence dataset. This method will hopefully facilitate the analysis of complex systems from exceedingly large, "big data" scientific datasets, as well as real-time streamed data. △ Less

Submitted 31 October, 2023; v1 submitted 1 July, 2023; originally announced July 2023.

Comments: 9 pages, 4 figures

Catalog of Ultraviolet Bright Stars (CUBS): Strategies for UV occultation measurements, planetary illumination modeling, and sky map analyses using hybrid IUE-Kurucz spectra

Authors: M. A. Velez, K. D. Retherford, V. Hue, J. A. Kammer, T. M. Becker, G. R. Gladstone, M. W. Davis, T. K. Greathouse, P. M. Molyneux, S. M. Brooks, U. Raut, M. H. Versteeg

Abstract: Ultraviolet spectroscopy is a powerful method to study planetary surface composition through reflectance measurements and atmospheric composition through stellar/solar occultations, transits of other planetary bodies, and direct imaging of airglow and auroral emissions. The next generation of ultraviolet spectrographs (UVS) on board ESA's JUICE (Jupiter Icy Moons Explorer) and NASA's Europa Clippe… ▽ More Ultraviolet spectroscopy is a powerful method to study planetary surface composition through reflectance measurements and atmospheric composition through stellar/solar occultations, transits of other planetary bodies, and direct imaging of airglow and auroral emissions. The next generation of ultraviolet spectrographs (UVS) on board ESA's JUICE (Jupiter Icy Moons Explorer) and NASA's Europa Clipper missions will perform such measurements of Jupiter and its moons in the early 2030's. This work presents a compilation of a detailed UV stellar catalog, named CUBS, of targets with high intensity in the 50-210 nm wavelength range with applications relevant to planetary spectroscopy. These applications include: 1) Planning and simulating occultations, including calibration measurements; 2) Modeling starlight illumination of dark, nightside planetary surfaces primarily lit by the sky; and 3) Studying the origin of diffuse galactic UV light as mapped by existing datasets from Juno-UVS and others. CUBS includes information drawn from resources such as the International Ultraviolet Explorer (IUE) catalog and SIMBAD. We have constructed model spectra at 0.1 nm resolution for almost 90,000 targets using Kurucz models and, when available, IUE spectra. CUBS also includes robust checks for agreement between the Kurucz models and the IUE data. We also present a tool for which our catalog can be used to identify the best candidates for stellar occultation observations, with applications for any UV instrument. We report on our methods for producing CUBS and discuss plans for its implementation during ongoing and upcoming planetary missions. △ Less

Submitted 7 March, 2023; originally announced March 2023.

Comments: 13 pages, 4 figures, submitted to JATIS

The Variation of Radiation Effective Dose Rates and Single Event Effect Rates at Aviation Altitudes with Magnetospheric Conditions and Geographic Location

Authors: Christopher S. W. Davis, Keith Ryden, Fan Lei, Ben Clewer, Alex Hands, Clive Dyer

Abstract: The geographic structure of radiation dose rates at aircraft altitudes in Earth's atmosphere during the irradiation of Earth by proton spectra from incoming solar particle events is examined using the recently developed MAIRE+ software. Conditions are examined under two incoming proton spectra, a low/hard spectral index and a high/soft spectral index spectra, which are representative of some of th… ▽ More The geographic structure of radiation dose rates at aircraft altitudes in Earth's atmosphere during the irradiation of Earth by proton spectra from incoming solar particle events is examined using the recently developed MAIRE+ software. Conditions are examined under two incoming proton spectra, a low/hard spectral index and a high/soft spectral index spectra, which are representative of some of the solar particle events that have caused reasonably sized Ground-Level Enhancements/Events (GLEs) over the past 70 years. It is found through the use of `cut-throughs' of the atmosphere, that the atmosphere can be divided into three volumes; a high dose rate polar region, a low dose rate equatorial region, and a transition region between the two. The location of these regions as a function of latitude, longitude and altitude is characterised. It is also found that the location of the transition region changes for different magnetospheric disturbance levels, implying that the total radiation dose rate an aircraft will experience if it passes through the transition region will be subject to large systematic uncertainties, particularly during the currently unknown levels of magnetospheric disturbance that a major solar event could cause. The impact that various magnetospheric conditions might have on dose rates that specific flight routes might experience is also discussed. △ Less

Submitted 15 December, 2022; originally announced December 2022.

Comments: 26 pages, 17 figures

The Effectiveness of a Simple Helmholtz coil-like Magnetic Shield at Reducing X-ray-like Background in Space-based X-ray Detectors

Authors: Christopher S. W. Davis, David Hall

Abstract: Both active and passive magnetic shielding have been used extensively during past and current X-ray astronomy missions to shield detectors from soft protons and electrons entering through telescope optics. However, simulations performed throughout the past decade have discovered that a significant proportion of X-ray-like background originates from secondary electrons produced in spacecraft shield… ▽ More Both active and passive magnetic shielding have been used extensively during past and current X-ray astronomy missions to shield detectors from soft protons and electrons entering through telescope optics. However, simulations performed throughout the past decade have discovered that a significant proportion of X-ray-like background originates from secondary electrons produced in spacecraft shielding surrounding X-ray detectors, which hit detectors isotropically from all directions. Here, the results from Geant4 simulations of a simple Helmholtz coil-like magnetic field surrounding a detector are presented, and it is found that a Helmholtz coil-like magnetic field is extremely effective at preventing secondary electrons from reaching the detector. This magnetic shielding method could remove almost all background associated with both backscattering electrons and fully absorbed soft electrons, which together are expected to account for approximately two thirds of the expected off-axis background in silicon-based X-ray detectors of several hundred microns in thickness. The magnetic field structure necessary for doing this could easily be produced using a set of solenoids or neodymium magnets providing that power requirements can be sufficiently optimised or neodymium fluorescence lines can be sufficiently attenuated, respectively. △ Less

Submitted 13 December, 2022; originally announced December 2022.

Comments: 20 pages, 6 figures

Report number: Vol. 9, Issue 2, 024008 (June 2023)

Journal ref: Journal of Astronomical Telescopes, Instruments, and Systems (2023)

Bead-Droplet Reactor for High-Fidelity Solid-Phase Enzymatic DNA Synthesis

Authors: Punnag Padhy, Mohammad Asif Zaman, Michael Anthony Jensen, Yao-Te Cheng, Yogi Huang, Ludwig Galambos, Ronald Wayne Davis, Lambertus Hesselink

Abstract: Solid-phase synthesis techniques underpin the synthesis of DNA, oligopeptides, oligosaccharides, and combinatorial libraries for drug discovery. State-of-the-art solid-phase synthesizers can produce oligonucleotides up to 200-300 nucleotides while using excess reagents. Accumulated errors over multiple reaction cycles prevent the synthesis of longer oligonucleotides for the genome scale engineerin… ▽ More Solid-phase synthesis techniques underpin the synthesis of DNA, oligopeptides, oligosaccharides, and combinatorial libraries for drug discovery. State-of-the-art solid-phase synthesizers can produce oligonucleotides up to 200-300 nucleotides while using excess reagents. Accumulated errors over multiple reaction cycles prevent the synthesis of longer oligonucleotides for the genome scale engineering of synthetic biological systems. The sources of these errors in synthesis columns remains poorly understood. Here we show that bead-bead stacking significantly contributes to reaction errors in columns by analyzing enzymatic coupling of fluorescently labelled nucleotides onto the initiated beads along with porosity, particle tracking and diffusion calculations. To circumvent stacking, we introduce dielectrophoretic bead-droplet reactor (DBDR); a novel approach to synthesize on individual microbeads within microdroplets. Dielectrophoretic force overcomes the droplet-medium interfacial tension to encapsulate and eject individual beads from microdroplets in a droplet microfluidic device. Faster reagent diffusion in droplets, and non-uniform electric field induced enhancement in reagent concentration at its surface can improve reaction fidelities in DBDR. Fluorescence comparisons suggest around 3-fold enhancement of reaction fidelity compared to columns. DBDR can potentially enable the high-purity synthesis of arbitrarily long strands of DNA to meet the emerging demands in healthcare, environment, agriculture, materials, and computing. △ Less

Submitted 1 June, 2023; v1 submitted 12 November, 2022; originally announced November 2022.

Anomaly detection in scientific data using joint statistical moments

Authors: Konduri Aditya, Hemanth Kolla, W. Philip Kegelmeyer, Timothy M. Shead, Julia Ling, Warren L. Davis IV

Abstract: We propose an anomaly detection method for multi-variate scientific data based on analysis of high-order joint moments. Using kurtosis as a reliable measure of outliers, we suggest that principal kurtosis vectors, by analogy to principal component analysis (PCA) vectors, signify the principal directions along which outliers appear. The inception of an anomaly, then, manifests as a change in the pr… ▽ More We propose an anomaly detection method for multi-variate scientific data based on analysis of high-order joint moments. Using kurtosis as a reliable measure of outliers, we suggest that principal kurtosis vectors, by analogy to principal component analysis (PCA) vectors, signify the principal directions along which outliers appear. The inception of an anomaly, then, manifests as a change in the principal values and vectors of kurtosis. Obtaining the principal kurtosis vectors requires decomposing a fourth order joint cumulant tensor for which we use a simple, computationally less expensive approach that involves performing a singular value decomposition (SVD) over the matricized tensor. We demonstrate the efficacy of this approach on synthetic data, and develop an algorithm to identify the occurrence of a spatial and/or temporal anomalous event in scientific phenomena. The algorithm decomposes the data into several spatial sub-domains and time steps to identify regions with such events. Feature moment metrics, based on the alignments of the principal kurtosis vectors, are computed at each sub-domain and time step for all features to quantify their relative importance towards the overall kurtosis in the data. Accordingly, spatial and temporal anomaly metrics for each sub-domain are proposed using the Hellinger distance of the feature moment metric distribution from a suitable nominal distribution. We apply the algorithm to a one-dimensional turbulent auto-ignition combustion case and demonstrate that the anomaly metrics reliably capture the occurrence of auto-ignition in relevant spatial sub-domains at the right time steps. △ Less

Submitted 13 August, 2018; originally announced August 2018.

Non-linear Evolution of Rayleigh-Taylor Instability in a Radiation Supported Atmosphere

Authors: Yan-Fei Jiang, Shane W. Davis, James Stone

Abstract: The non-linear regime of Rayleigh-Taylor instability (RTI) in a radiation supported atmosphere, consisting of two uniform fluids with different densities, is studied numerically. We perform simulations using our recently developed numerical algorithm for multi-dimensional radiation hydrodynamics based on a variable Eddington tensor as implemented in Athena, focusing on the regime where scattering… ▽ More The non-linear regime of Rayleigh-Taylor instability (RTI) in a radiation supported atmosphere, consisting of two uniform fluids with different densities, is studied numerically. We perform simulations using our recently developed numerical algorithm for multi-dimensional radiation hydrodynamics based on a variable Eddington tensor as implemented in Athena, focusing on the regime where scattering opacity greatly exceeds absorption opacity. We find that the radiation field can reduce the growth and mixing rate of RTI, but this reduction is only significant when radiation pressure significantly exceeds gas pressure. Small scale structures are also suppressed in this case. In the non-linear regime, dense fingers sink faster than rarefied bubbles can rise, leading to asymmetric structures about the interface. By comparing the calculations that use a variable Eddington tensor (VET) versus the Eddington approximation, we demonstrate that anisotropy in the radiation field can affect the non-linear development of RTI significantly. We also examine the disruption of a shell of cold gas being accelerated by strong radiation pressure, motivated by models of radiation driven outflows in ultraluminous infrared galaxies. We find that when the growth rate of RTI is smaller than acceleration time scale, the amount of gas that would be pushed away by the radiation field is reduced due to RTI. △ Less

Submitted 7 December, 2012; originally announced December 2012.

Comments: 15 pages, 1 table, 13 figures, accepted by ApJ

Journal ref: 2013, ApJ 763, 102

A Godunov Method for Multidimensional Radiation Magnetohydrodynamics based on a variable Eddington tensor

Authors: Yan-Fei Jiang, James M. Stone, Shane W. Davis

Abstract: We describe a numerical algorithm to integrate the equations of radiation magnetohydrodynamics in multidimensions using Godunov methods. This algorithm solves the radiation moment equations in the mixed frame, without invoking any diffusion-like approximations. The moment equations are closed using a variable Eddington tensor whose components are calculated from a formal solution of the transfer e… ▽ More We describe a numerical algorithm to integrate the equations of radiation magnetohydrodynamics in multidimensions using Godunov methods. This algorithm solves the radiation moment equations in the mixed frame, without invoking any diffusion-like approximations. The moment equations are closed using a variable Eddington tensor whose components are calculated from a formal solution of the transfer equation at a large number of angles using the method of short characteristics. We use a comprehensive test suite to verify the algorithm, including convergence tests of radiation-modified linear acoustic and magnetosonic waves, the structure of radiation modified shocks, and two-dimensional tests of photon bubble instability and the ablation of dense clouds by an intense radiation field. These tests cover a very wide range of regimes, including both optically thick and thin flows, and ratios of the radiation to gas pressure of at least 10^{-4} to 10^{4}. Across most of the parameter space, we find the method is accurate. However, the tests also reveal there are regimes where the method needs improvement, for example when both the radiation pressure and absorption opacity are very large. We suggest modifications to the algorithm that will improve accuracy in this case. We discuss the advantages of this method over those based on flux-limited diffusion. In particular, we find the method is not only substantially more accurate, but often no more expensive than the diffusion approximation for our intended applications. △ Less

Submitted 10 January, 2012; originally announced January 2012.

Comments: 42 pages, 22 figures, 2 tables, accepted by ApJS

Journal ref: ApJS, 2012, 199, 14

Levi-Civita Effect in the polarizable vacuum (PV) representation of general relativity

Authors: H. E. Puthoff, Claudio Maccone, Eric W. Davis

Abstract: The polarizable vacuum (PV) representation of general relativity (GR), derived from a model by Dicke and related to the "TH-epsilon-mu" formalism used in comparative studies of gravitational theories, provides for a compact derivation of the Levi-Civita Effect (both magnetic and electric), herein demonstrated. The polarizable vacuum (PV) representation of general relativity (GR), derived from a model by Dicke and related to the "TH-epsilon-mu" formalism used in comparative studies of gravitational theories, provides for a compact derivation of the Levi-Civita Effect (both magnetic and electric), herein demonstrated. △ Less

Submitted 10 March, 2004; originally announced March 2004.

Comments: 8 pages