arXiv subjects

B. Heacock

Publications and source records attributed to B. Heacock.

12 recordsLinked to original sources

arXiv2026

Fast Microwave-free State Preparation and Measurement of Superconducting Qubits

Fast, high-fidelity, scalable state preparation and measurement is critical to the realization of a quantum computing system. The state-of-the-art methods for preparation and readout of superconducting qubits require finely tuned microwave signals and ~100 ns of measurement time, which are major obstacles to the scalability and performance of superconducting quantum computers. Here, we have demonstrated novel, microwave-free methods for both preparation and readout of superconducting qubits with >99% fidelity in only 10 ns for either operation while maintaining qubit coherence. This technology is compatible with scalable superconducting digital control systems, and using quantum flux parametrons for amplification, we demonstrated full quantum-to-digital conversion in only 15 ns, which is an order of magnitude faster than state-of-the-art microwave-based techniques.

quant-ph↗

arXiv2025

Design and Monte Carlo Simulation of a Phase Grating Moir\'e Neutron Interferometer to Measure the Gravitational Constant

The gravitational constant (G) is the least precisely known fundamental constant of nature, with persistent and significant discrepancies between measurement methods. New techniques for measuring G with systematic effects different from commonly applied pendulum methods are required. Neutrons are convenient probes of gravitational forces as they are both massive and electrically neutral, properties that allowed a single-crystal neutron interferometer (NI) to achieve the first experimental demonstration of gravitationally induced quantum interference. Despite this, the limitation of single-crystal NIs to monoenergetic beams significantly reduces neutron flux, making precision gravitational measurements unfeasible. A new NI design called the phase-grating moir\'{e} interferometer (PGMI) has been shown to increase neutron flux by orders of magnitude while allowing grating separation that maintains similar interferometer area to previous NI devices. Here, we propose and describe an experiment to measure G using the PGMI to a precision comparable to measurements from the CODATA 2022 evaluation. A Monte Carlo model for incorporating nonlinear potentials into a PGMI is introduced. This model is used to evaluate sources of systematic uncertainty and quantify the uncertainty in G arising from these effects. The effect of lunar gravitation on a torsion pendulum experiment from CODATA 2022 is calculated, and the need for possible correction factors is demonstrated. This work demonstrates that a neutron PGMI can be used to measure G to $150$ parts-per-million in the near term with the potential to achieve greater precision in future experimental designs.

physics.ins-det↗

arXiv2024

Achieving a Near-Ideal Silicon Crystal Neutron Interferometer using Sub-Micron Fabrication Techniques

Perfect-crystal neutron interferometry which is analogous to Mach-Zehnder interferometry, uses Bragg diffraction to form interfering neutron paths. The measured phase shifts can be used to probe many types of interactions whether it be nuclear, electromagnetic, gravitational, or topological in nature. For a perfect-crystal interferometer to preserve coherence, the crystal must possess a high degree of dimensional tolerance as well as being relatively defect-free with minimal internal stresses. In the past, perfect-crystal neutron interferometers have been produced by a two step process. First, a resin diamond wheel would be used to remove excess material and shape the interferometer. Afterword, the crystal would be etched in order to remove surface defects and elevate strains. This process has had limitations in terms of repeatability and in maximizing the final contrast, or fringe visibility, of the interferometer. We have tested various fabrication and post-fabrication techniques on a single perfect-crystal neutron interferometer and measured the interferometer's performance at each step. Here we report a robust, repeatable non-etching fabrication process with high final contrast. For the interferometer used in this work, we achieved contrasts of greater than 90% several separate times and ultimately finished with an interferometer that has 92% contrast and a uniform phase distribution.

physics.ins-det↗

arXiv2022

Three-Dimensional Neutron Far-Field Tomography of a Bulk Skyrmion Lattice

Skyrmions are topologically-protected spin textures thought to nucleate and annihilate on points of vanishing magnetization, called Bloch points. However, owing to a lack of bulk techniques, experimental visualizations of skyrmion lattices and their stabilization through defects in three-dimensions remain elusive. Here, we present a tomographic algorithm applied to a Co$_8$Zn$_8$Mn$_4$ skyrmion lattice host, processing multi-projection small angle neutron scattering measurements to generate mean scattering feature reconstructions (MSFR) of the bulk spin textures. Digital phantoms validated the algorithm; reconstructions of the sample show a disordered skyrmion lattice with a topological saturation of 63~\%, exhibiting three-dimensional topological transitions through two different emergent (anti)monopole defect pathways with densities of 147~$\mu$m$^{-3}$ and 21~$\mu \mathrm{m}^{-3}$ for branching and segmentation events, respectively. Our techniques produce experimentally-informed visualizations of bulk skyrmion lattice structures and defects, enabling future bulk studies over a wide variety of sample shapes and chemistries, magnetic phases, and external parameters.

cond-mat.mtrl-sci↗

arXiv2021

Next-generation high transmission neutron optical devices utilizing micro-machined structures

Neutrons have emerged as a unique probe at the forefront of modern material science, unrivaled in their penetrating abilities. A major challenge stems from the fact that neutron optical devices are limited to refractive indices on the order of $n\approx 1 \pm 10^{-5}$. By exploiting advances in precision manufacturing, we have designed and constructed a micro-meter period triangular grating with a high aspect ratio of $14.3$. The manufacturing quality is demonstrated with white-light interferometric data and microscope imaging. Neutron scattering experiment results are presented, showing agreement to refraction modelling. The capabilities of neutron Fresnel lenses based on this design are contrasted to existing neutron focusing techniques and the path separation of a prism-based neutron interferometer is estimated.

physics.app-ph↗

arXiv2021

Skyrmion Alignment and Pinning Effects in a Disordered Multi-Phase Skyrmion Material Co8Zn8Mn4

Underlying disorder in skyrmion materials may both inhibit and facilitate skyrmion reorientations and changes in topology. The identification of these disorder-induced topologically active regimes is critical to realizing robust skyrmion spintronic implementations, yet few studies exist for disordered bulk samples. Here, we employ small-angle neutron scattering (SANS) and micromagnetic simulations to examine the influence of skyrmion order on skyrmion lattice formation, transition, and reorientation dynamics across the phase space of a disordered polycrystalline Co$_{8}$Zn$_{8}$Mn$_{4}$ bulk sample. Our measurements reveal a new disordered-to-ordered skyrmion square lattice transition pathway characterized by the novel promotion of four-fold order in SANS and accompanied by a change in topology of the system, reinforced through micromagnetic simulations. Pinning responses are observed to dominate skyrmion dynamics in the metastable triangular lattice phase, enhancing skyrmion stabilization through a remarkable and previously undetected skyrmion memory effect which reproduces previous ordering processes and persists in zero field. These results uncover the cooperative interplay of anisotropy and disorder in skyrmion formation and restructuring dynamics, establishing new tunable pathways for skyrmion manipulation.

cond-mat.mtrl-sci↗

arXiv2021

Generalizing the Quantum Information Model for Dynamic Diffraction

The development of novel neutron optics devices that rely on perfect crystals and nano-scale features are ushering a new generation of neutron science experiments, from fundamental physics to material characterization of emerging quantum materials. However, the standard theory of dynamical diffraction (DD) that analyzes neutron propagation through perfect crystals does not consider complex geometries, deformations, and/or imperfections which are now becoming a relevant systematic effect in high precision interferometric experiments. In this work, we expand upon a quantum information (QI) model of DD that is based on propagating a particle through a lattice of unitary quantum gates. We show that the model output is mathematically equivalent to the spherical wave solution of the Takagi-Taupin equations when in the appropriate limit, and that the model can be extended to the Bragg as well as the Laue-Bragg geometry where it is consistent with experimental data. The presented results demonstrate the universality of the QI model and its potential for modeling scenarios that are beyond the scope of the standard theory of DD.

quant-ph↗

arXiv2019

A Precision Measurement of the Neutron Scattering Length of He-4 Using Neutron Interferometry

We report a 0.08 % measurement of the bound neutron scattering length of $^4$He using neutron interferometry. The result is $b = (3.0982 \pm 0.0021 \mbox{ [stat]} \pm 0.0014 \mbox{ [sys]}) \mbox{ fm}$. The corresponding free atomic scattering length is $a = (2.4746 \pm 0.0017 \mbox{ [stat]} \pm 0.0011 \mbox{ [sys]}) \mbox{ fm}$. With this result the world average becomes $b = (3.0993 \pm 0.0025)$ fm, a 2 % downward shift and a reduction in uncertainty by more than a factor of six. Our result is in disagreement with a previous neutron interferometric measurement but is in good agreement with earlier measurements using neutron transmission.

nucl-ex↗

arXiv2018

Optimization of neutron diffraction from phase-gratings

The recent development of phase-grating moir\'e neutron interferometry promises a wide range of impactful experiments from dark-field imaging of material microstructure to precise measurements of fundamental constants. However, the contrast of 3 % obtained using this moir\'e interferometer was well below the theoretical prediction of 30 % using ideal gratings. It is suspected that non-ideal aspects of the phase-gratings was a leading contributor to this deficiency and that phase-gratings needed to be quantitatively assessed and optimized. Here we characterize neutron diffraction from phase-gratings using Bragg diffraction crystals to determine the optimal phase-grating orientations. We show well-defined diffraction peaks and explore perturbations to the diffraction peaks and the effects on interferometer contrast as a function of grating alignment. This technique promises to improve the contrast of the grating interferometers by providing in-situ aides to grating alignment.

physics.ins-det↗

arXiv2018

Sub-micrometer resolution neutron tomography

We demonstrate a neutron tomography technique with sub-micrometer spatial resolution. Our method consists of measuring neutron diffraction spectra using a double crystal diffractometer as a function of sample rotation and then using a phase retrieval algorithm followed by tomographic reconstruction to generate a density map of the sample. In this first demonstration, silicon phase-gratings are used as samples, the periodic structure of which allows the shape of the gratings to be imaged without the need of position sensitive detectors. Topological features found in the reconstructions also appear in scanning electron micrographs. The reconstructions have a resolution of about 300 nm, which is over an order of magnitude smaller than the resolution of radiographic, phase contrast, differential phase contrast, and dark field neutron tomography methods. Further optimization of the underlying phase recovery and tomographic reconstruction algorithm is also considered.

physics.ins-det↗

arXiv2017

Three Phase-Grating Moire Neutron Interferometer for Large Interferometer Area Applications

We demonstrate a three phase-grating neutron interferometer as a robust candidate for large area interferometry applications and characterization of materials. This novel far-field moire technique allows for broad wavelength acceptance and relaxed requirements related to fabrication and alignment, circumventing the main obstacles associated with perfect crystal neutron interferometry. Interference fringes were observed with a total interferometer length of four meters, and the effects of an aluminum 6061 alloy sample on the coherence of the system was examined. Experiments to measure the autocorrelation length of samples and the universal gravitational constant are proposed and discussed.

physics.ins-det↗

arXiv2016

Neutron Limit on the Strongly-Coupled Chameleon Field

The physical origin of the dark energy that causes the accelerated expansion rate of the universe is one of the major open questions of cosmology. One set of theories postulates the existence of a self-interacting scalar field for dark energy coupling to matter. In the chameleon dark energy theory, this coupling induces a screening mechanism such that the field amplitude is nonzero in empty space but is greatly suppressed in regions of terrestrial matter density. However measurements performed under appropriate vacuum conditions can enable the chameleon field to appear in the apparatus, where it can be subjected to laboratory experiments. Here we report the most stringent upper bound on the free neutron-chameleon coupling in the strongly-coupled limit of the chameleon theory using neutron interferometric techniques. Our experiment sought the chameleon field through the relative phase shift it would induce along one of the neutron paths inside a perfect crystal neutron interferometer. The amplitude of the chameleon field was actively modulated by varying the millibar pressures inside a dual-chamber aluminum cell. We report a 95% confidence level upper bound on the neutron-chameleon coupling $β$ ranging from $β< 4.7\times 10^6$ for a Ratra-Peebles index of n = 1 in the nonlinear scalar field potential to $β< 2.4\times 10^7$ for n = 6, one order of magnitude more sensitive than the most recent free neutron limit for intermediate n. Similar experiments can explore the full parameter range for chameleon dark energy in the foreseeable future.

astro-ph.CO↗