arXiv subjects

Brian Fields

Publications and source records attributed to Brian Fields.

17 recordsLinked to original sources

arXiv2025

Demonstration of a Logical Architecture Uniting Motion and In-Place Entanglement

We demonstrate a logical neutral atom architecture that integrates atom motion with in-place entanglement to achieve lower overheads than entangling-zone approaches. Using a 114-qubit device, we perform three proof-of-principle logical-qubit experiments. First, we implement a pre-compiled, non-scalable variant of Shor's algorithm, observing improved logical-over-physical performance, including with loss correction and leakage detection, achieving up to a 2x reduction in TVD. Second, we construct constant-depth logical CX ladders; on current hardware these execute with serial entangling operations, yet still yield 2-4x lower error for 8 and 12 logical qubits. Third, we prepare the [[16,4,4]] code and perform single-round decoding with post-processed error correction, achieving 8x improvement on logical vs physical. These results demonstrate how combining motion with in-place entanglement offers lower overhead than entangling-zone approaches.

quant-ph↗

arXiv2023

Synergies between interstellar dust and heliospheric science with an Interstellar Probe

We discuss the synergies between heliospheric and dust science, the open science questions, the technological endeavors and programmatic aspects that are important to maintain or develop in the decade to come. In particular, we illustrate how we can use interstellar dust in the solar system as a tracer for the (dynamic) heliosphere properties, and emphasize the fairly unexplored, but potentially important science question of the role of cosmic dust in heliospheric and astrospheric physics. We show that an Interstellar Probe mission with a dedicated dust suite would bring unprecedented advances to interstellar dust research, and can also contribute-through measuring dust - to heliospheric science. This can, in particular, be done well if we work in synergy with other missions inside the solar system, thereby using multiple vantage points in space to measure the dust as it `rolls' into the heliosphere. Such synergies between missions inside the solar system and far out are crucial for disentangling the spatially and temporally varying dust flow. Finally, we highlight the relevant instrumentation and its suitability for contributing to finding answers to the research questions.

astro-ph.IM↗

arXiv2019

All-sky Medium Energy Gamma-ray Observatory: Exploring the Extreme Multimessenger Universe

The All-sky Medium Energy Gamma-ray Observatory (AMEGO) is a probe class mission concept that will provide essential contributions to multimessenger astrophysics in the late 2020s and beyond. AMEGO combines high sensitivity in the 200 keV to 10 GeV energy range with a wide field of view, good spectral resolution, and polarization sensitivity. Therefore, AMEGO is key in the study of multimessenger astrophysical objects that have unique signatures in the gamma-ray regime, such as neutron star mergers, supernovae, and flaring active galactic nuclei. The order-of-magnitude improvement compared to previous MeV missions also enables discoveries of a wide range of phenomena whose energy output peaks in the relatively unexplored medium-energy gamma-ray band.

astro-ph.IM↗

arXiv2019

Microring resonators on a membrane optical circuit for atom-light interactions

We describe the design and fabrication of a scalable atom-light photonic interface based on a silicon nitride microring resonator on a transparent silicon dioxide-nitride multi-layer membrane. This new photonic platform is fully compatible with freespace cold atom laser cooling, stable trapping, and sorting at around $100~$nm from the microring surface, permitting the formation of an organized, strongly interacting atom-photonic hybrid lattice. We demonstrate small radius ($R\sim$16$\mu$m) microring and racetrack resonators with a high quality factor $Q=3.2\times 10^5$, projecting a single atom cooperativity parameter of $C=25$ and a vacuum Rabi frequency of $2g= 2\pi\times 340~$MHz for trapped cesium atoms interacting with a microring resonator mode. We show that the quality factor is currently limited by the surface roughness of the multi-layer membrane, grown using low pressure chemical vapor deposition (LPCVD) processes. We discuss possible further improvements to a quality factor above $Q>5\times10^6$, potentially achieving single atom cooperativity parameter of $C > 500$ for strong single atom-photon coupling.

quant-ph↗

arXiv2019

Energetic Particles of Cosmic Accelerators I: Galactic Accelerators

The high-energy universe has revealed that energetic particles are ubiquitous in the cosmos and play a vital role in the cultivation of cosmic environments on all scales. Energetic particles in our own galaxy, galactic cosmic rays (GCRs), engage in a complex interplay with the interstellar medium and magnetic fields in the galaxy, giving rise to many of its key characteristics. This White Paper is the first of a two-part series highlighting the most well-known high-energy cosmic accelerators and contributions that MeV gamma-ray astronomy will bring to understanding their energetic particle phenomena. The focus of this white paper is galactic cosmic rays, supernova remnants, protostellar jets and superbubbles, and colliding wind binaries.

astro-ph.HE↗

arXiv2019

Energetic Particles of Cosmic Accelerators II: Active Galactic Nuclei and Gamma-ray Bursts

The high-energy universe has revealed that energetic particles are ubiquitous in the cosmos and play a vital role in the cultivation of cosmic environments on all scales. Though they play a key role in cultivating the cosmological environment and/or enabling our studies of it, there is still much we do not know about AGNs and GRBs, particularly the avenue in which and through which they supply radiation and energetic particles, namely their jets. This White Paper is the second of a two-part series highlighting the most well-known high-energy cosmic accelerators and contributions that MeV gamma-ray astronomy will bring to understanding their energetic particle phenomena. The focus of this white paper is active galactic nuclei and gamma-ray bursts.

astro-ph.HE↗

arXiv2019

Catching Element Formation In The Act

Gamma-ray astronomy explores the most energetic photons in nature to address some of the most pressing puzzles in contemporary astrophysics. It encompasses a wide range of objects and phenomena: stars, supernovae, novae, neutron stars, stellar-mass black holes, nucleosynthesis, the interstellar medium, cosmic rays and relativistic-particle acceleration, and the evolution of galaxies. MeV gamma-rays provide a unique probe of nuclear processes in astronomy, directly measuring radioactive decay, nuclear de-excitation, and positron annihilation. The substantial information carried by gamma-ray photons allows us to see deeper into these objects, the bulk of the power is often emitted at gamma-ray energies, and radioactivity provides a natural physical clock that adds unique information. New science will be driven by time-domain population studies at gamma-ray energies. This science is enabled by next-generation gamma-ray instruments with one to two orders of magnitude better sensitivity, larger sky coverage, and faster cadence than all previous gamma-ray instruments. This transformative capability permits: (a) the accurate identification of the gamma-ray emitting objects and correlations with observations taken at other wavelengths and with other messengers; (b) construction of new gamma-ray maps of the Milky Way and other nearby galaxies where extended regions are distinguished from point sources; and (c) considerable serendipitous science of scarce events -- nearby neutron star mergers, for example. Advances in technology push the performance of new gamma-ray instruments to address a wide set of astrophysical questions.

astro-ph.HE↗

arXiv2015

Spatial and Spectral Modeling of the Gamma-ray Distribution in the Large Magellanic Cloud

We perform spatial and spectral analyses of the Large Magellanic Cloud (LMC) gamma-ray emission collected over 66 months by the Fermi Gamma-ray Space Telescope. In our spatial analysis, we model the LMC cosmic-ray distribution and gamma-ray production using observed maps of the LMC interstellar medium, star formation history, interstellar radiation field, and synchrotron emission. We use bootstrapping of the data to quantify the robustness of spatial model performance. We model the LMC gamma-ray spectrum using fitting functions derived from the physics of $\pi^0$ decay, bremsstrahlung, and inverse Compton scattering. We find the integrated gamma-ray flux of the LMC from 200 MeV to 20 GeV to be $1.38 \pm 0.02 \times 10^{-7}$ ph cm$^{-2}$ s$^{-1}$, of which we attribute about 10% to inverse Compton scattering and 40% to bremsstrahlung. From our work, we conclude that the spectral index of the LMC cosmic-ray proton population is 2.4$\pm$0.2, and we find that cosmic-ray energy loss through gamma-ray production is concentrated within a few hundred pc of acceleration sites. Assuming cosmic-ray energy equipartition with magnetic fields, we estimate LMC cosmic rays encounter an average magnetic field strength ~3 $\mu$G.

astro-ph.HE↗

arXiv2015

High Energy Polarization of Blazars : Detection Prospects

Emission from blazar jets in the ultraviolet, optical, and infrared is polarized. If these low-energy photons were inverse-Compton scattered, the upscattered high-energy photons retain a fraction of the polarization. Current and future X-ray and gamma-ray polarimeters such as INTEGRAL-SPI, PoGOLITE, X-Calibur, Gamma-Ray Burst Polarimeter, GEMS-like missions, ASTRO-H, and POLARIX have the potential to discover polarized X-rays and gamma-rays from blazar jets for the first time. Detection of such polarization will open a qualitatively new window into high-energy blazar emission; actual measurements of polarization degree and angle will quantitatively test theories of jet emission mechanisms. We examine the detection prospects of blazars by these polarimetry missions using examples of 3C 279, PKS 1510-089, and 3C 454.3, bright sources with relatively high degrees of low-energy polarization. We conclude that while balloon polarimeters will be challenged to detect blazars within reasonable observational times (with X-Calibur offering the most promising prospects), space-based missions should detect the brightest blazars for polarization fractions down to a few percent. Typical flaring activity of blazars could boost the overall number of polarimetric detections by nearly a factor of five to six purely accounting for flux increase of the brightest of the comprehensive, all-sky, Fermi-LAT blazar distribution. The instantaneous increase in the number of detections is approximately a factor of two, assuming a duty cycle of 20% for every source. The detectability of particular blazars may be reduced if variations in the flux and polarization fraction are anticorrelated. Simultaneous use of variability and polarization trends could guide the selection of blazars for high-energy polarimetric observations.

astro-ph.HE↗

arXiv2015

New Bounds for Axions and Axion-Like Particles with keV-GeV Masses

We give updated constraints on hypothetical light bosons with a two-photon coupling such as axions or axion-like particles (ALPs). We focus on masses and lifetimes where decays happen near big bang nucleosynthesis (BBN), thus altering the baryon-to-photon ratio and number of relativistic degrees of freedom between the BBN epoch and the cosmic microwave background (CMB) last scattering epoch, in particular such that $N_{\rm eff}^{\rm CMB} < N_{\rm eff}^{\rm BBN}$ and $\eta^{\rm CMB} < \eta^{\rm BBN}$. New constraints presented here come from Planck measurements of the CMB power spectrum combined with the latest inferences of primordial $^4$He and D/H abundances. We find that a previously allowed region in parameter space near $m=1\,\rm MeV$ and $\tau=100\,\rm ms$, consistent with a QCD axion arising from a symmetry breaking near the electroweak scale, is now ruled out at $>3\sigma$ by the combination of CMB+D/H measurements if only ALPs and three thermalized neutrino species contribute to $N_{\rm eff}$. The bound relaxes if there are additional light degrees of freedom present which, in this scenario, have their contribution limited to $\Delta N_{\rm eff}=1.1\pm0.3$. We give forecasts showing that a number of experiments are expected to reach the sensitivity needed to further test this region, such as Stage-IV CMB and SUPER-KEKB, the latter a direct test insensitive to any extra degrees of freedom.

astro-ph.CO↗

arXiv2006

The Cosmological Parameters 2006

This is a review article for The Review of Particle Physics 2006 (aka the Particle Data Book). It forms a compact review of knowledge of the cosmological parameters as at May 2006. Topics included are Parametrizing the Universe; Extensions to the standard model; Probes; Bringing observations together; Outlook for the future.

astro-ph↗

arXiv2004

Big Bang Nucleosynthesis (in "The Review of Particle Properties" 2004)

A critical review is given of the current status of cosmological nucleosynthesis. In the framework of the standard model with 3 types of relativistic neutrinos, the baryon-to-photon ratio, η, corresponding to the inferred primordial abundances of helium-4 and lithium-7 is presently ~2 σbelow the value implied by the abundance of deuterium. The latter value is also coincident with the independent determination of ηfrom WMAP observations of CMB anisotropy. However taking systematic uncertainties in the abundance estimates into account, there is overall concordance in the range η= (3.4 - 6.9) x 10^{-10} @ 95% c.l. corresponding to a cosmological baryon density Ω_B h^2 = 0.012 - 0.025. If the above discrepancy is due to a neutrino chemical potential, then upto 7.1 effective neutrino species are allowed by nucleosynthesis. Other constraints on new physics are briefly discussed.

astro-ph↗

arXiv2000

Death of Stellar Baryonic Dark Matter Candidates

The nature of the dark matter in the Universe is one of the outstanding questions in astrophysics. In this talk, I address possible stellar baryonic contributions to the 50-90% of our Galaxy that is made of unknown dark matter. First I show that faint stars and brown dwarfs constitute only a few percent of the mass of the Galaxy. Next, I show that stellar remnants, including white dwarfs and neutron stars, are also insufficient in abundance to explain all the dark matter of the Galaxy. High energy gamma-rays observed in HEGRA data place the most robust constraints, $Ω_{WD} < 3 \times 10^{-3} h^{-1}$, where $h$ is the Hubble constant in units of 100 km s$^{-1}$ Mpc$^{-1}$. Overproduction of chemical abundances (carbon, nitrogen, and helium) provide the most stringent constraints, $Ω_{WD} < 2 \times 10^{-4} h^{-1}$. Comparison with recent updates of microlensing data are also made. According to the gamma-ray limit, all Massive Compact Halo Objects seen by the experiments (Machos) can be white dwarfs if one takes the extreme numbers; however, from chemical overproduction limits, NOT all Machos can be white dwarfs. Comments on recent observations of the infrared background and of white dwarfs are also made. In conclusion, a nonbaryonic component in the Halo seems to be required.

astro-ph↗

arXiv1999

Limits on Stellar Objects as the Dark Matter of Our Halo: Nonbaryonic Dark Matter Seems to be Required

The nature of the dark matter in the Halo of our Galaxy remains a mystery. Arguments are presented that the dark matter does not consist of ordinary stellar or substellar objects, i.e., the dark matter is not made of faint stars, brown dwarfs, white dwarfs, or neutron stars. In fact, faint stars and brown dwarfs constitute no more than a few percent of the mass of our Galaxy, and stellar remnants must satisfy $Ω_{WD} \leq 3 \times 10^{-3} h^{-1}$, where $h$ is the Hubble constant in units of 100 km/s Mpc^{-1}. On theoretical grounds one is then pushed to more exotic explanations. Indeed a nonbaryonic component in the Halo seems to be required.

astro-ph↗

arXiv1999

What are Machos? Limits on Stellar Objects as the Dark Matter of our Halo

The nature of the Massive Compact Halo objects seen in microlensing experiments and interpreted as dark matter in the Halo of our Galaxy remains a mystery. Arguments are presented that these events are probably not ordinary stellar or substellar objects, i.e., they are probably not faint stars, brown dwarfs, white dwarfs, or neutron stars. On theoretical grounds one is then pushed to either exotic explanations or a "no-Macho" Halo (in which the Machos reside elsewhere than in the Halo). Indeed a nonbaryonic component in the Halo seems to be required.

astro-ph↗

arXiv1995

On the Evoution of the Light Elements I. D, He-3, and He-4

The light elements D, \he3, \he4, and \li7 are produced in big bang nucleosynthesis and undergo changes in their abundances due to galactic processing. Since one may observe most of these elements only in contemporary environments, knowledge of the intervening evolution is necessary for determining the observational constraints on primordial nucleosynthesis. Chemical and stellar evolution model dependences in light element evolution are systematically investigated via a comparison of 1460 possible chemical evolution scenarios and of stellar nucleosynthesis yields, all of which have been selected to fit solar neighborhood C, N, O, and Fe abundances as well as the observed local gas density and gas mass fraction. The light element evolution and solar system yields in these models are found to span a wide range, explicitly demonstrating the model dependence. The range of model dependence for D, \he3, and \he4 solar abundances is calculated, and its sensitivity to the heavy element constraints is noted. The chemical evolution contribution to the uncertainty in the observed primordial light element abundances is estimated, and the effects of this uncertainty on big bang nucleosynthesis results are discussed. The predictions for the light elements are found to be correlated; the extent and physical origin of these correlations is discussed. D and \he3 evolution is found to have significant model dependence, however, the dominant factor determining their solar and interstellar abundances is their primordial abundance. In addition, \he3 is found to be very sensitive to the details of processing in low mass stars. \he4 yields are shown to be very model dependent; in particular, both the introduction of mass loss and the possibly very high \he4 stellar yields in the

astro-ph↗

arXiv1994

Cosmic Ray Models for Early Galactic Lithium, Beryllium, and Boron Production

To understand better the early galactic production of Li, Be, and B by cosmic ray spallation and fusion reactions, the dependence of these production rates on cosmic ray models and model parameters is examined. The sensitivity of elemental and isotopic production to the cosmic ray pathlength magnitude and energy dependence, source spectrum, spallation kinematics, and cross section uncertainties is studied. Changes in these model features, particularly those features related to confinement, are shown to alter the Be- and B-versus-Fe slopes {}from a na\"ıve quadratic relation. The implications of our results for the diffuse $γ$-ray background are examined, and the role of chemical evolution and its relation to our results is noted. It is also noted that the unmeasured high energy behavior of $α+α$ fusion can lead to effects as large as a factor of 2 in the resultant yields. Future data should enable Population II Li, Be, and B abundances to constrain cosmic ray models for the early Galaxy.

astro-ph↗