arXiv subjects

Mark Baker

Publications and source records attributed to Mark Baker.

14 recordsLinked to original sources

arXiv2024

Measuring Blackbody Noise in Silica Optical Fibres for Quantum and Classical Communication

Deployment of practical quantum networks, which operate at or near single photon levels, requires carefully quantifying noise processes. We investigate noise due to blackbody radiation emitted into the guided mode of silica single mode optical fibres near room temperature, which to date is under-explored in the literature. We utilise a single photon avalanche detector and lock in detection to measure $\approx$0.1 photons/s/THz ($\approx$-170dBm/THz) at 40{\deg}C near the optically thick limit of 20km in silica fibre. We also measure a coarse spectrum to validate the blackbody behaviour, and observe a prominent anomaly around the 1430nm CWDM channel, likely due to -OH impurities. Though the magnitude of this noise is small, it is additive noise which imposes a fundamental limit in raw fidelity in quantum communication, and a fundamental noise floor in classical communication over optical fibres.

physics.optics↗

arXiv2022

Viability of rotation sensing using phonon interferometry in Bose-Einstein condensates

We demonstrate the use of a ring-shaped Bose-Einstein condensate as a rotation sensor by measuring the interference between two counter-propagating phonon modes imprinted azimuthally around the ring. We observe rapid decay of the excitations, quantified by quality factors of at most $Q \approx 27$. We numerically model our experiment using the c-field methodology, allowing us to estimate the parameters that maximise the performance of our sensor. We explore the damping mechanisms underlying the observed phonon decay, and identify two distinct Landau scattering processes that each dominate at different driving amplitudes and temperatures. Our simulations reveal that $Q$ is limited by strong damping of phonons even in the zero temperature limit. We perform an experimental proof-of-principle rotation measurement using persistent currents imprinted around the ring. We demonstrate a rotation sensitivity of up to $\Delta \Omega \approx 0.3$ rad/s from a single image, with a theoretically achievable value of $\Delta \Omega \approx 0.04$ rad/s in the atomic shot-noise limit. This is a significant improvement over the shot-noise-limited $\Delta \Omega \approx 1$ rad/s sensitivity obtained by Marti et al. [Phys. Rev. A 91, 013602 (2015)] for a similar setup.

cond-mat.quant-gas↗

arXiv2021

Neutron Spin Structure from e-3He Scattering with Double Spectator Tagging at the Electron-Ion Collider

The spin structure function of the neutron is traditionally determined by measuring the spin asymmetry of inclusive electron deep inelastic scattering (DIS) off polarized3He nuclei. In such experiments, nuclear effects can lead to large model dependencies in the interpretation of experimental data. Here we study the feasibility of suppressing such model dependencies by tagging both spectator protons in the process of DIS off neutrons in3He at the forthcoming Electron-Ion Collider (EIC). This allows reconstructing the momentum of the struck neutron to ensure it was nearly at rest in the initial state, thereby reducing sensitivity to nuclear corrections, and suppress contributions from electron DIS off protonsin3He. Using realistic accelerator and detector configurations, we find that the EIC can probe the neutron spin structure from xB of 0.003 to 0.651. We further find that the double spectator tagging method results in reduced uncertainties bya factor of 4 on the extracted neutron spin asymmetries over all kinematics, and by a factor of 10 in the low-xB region,thereby providing valuable insight to the spin and flavor structure of nucleons

nucl-ex↗

arXiv2021

Dynamic high-resolution optical trapping of ultracold atoms

All light has structure, but only recently it has become possible to construct highly controllable and precise potentials so that most laboratories can harness light for their specific applications. In this chapter, we review the emerging techniques for high-resolution and configurable optical trapping of ultracold atoms. We focus on optical deflectors and spatial light modulators in the Fourier and direct imaging configurations. These optical techniques have enabled significant progress in studies of superfluid dynamics, single-atom trapping, and underlie the emerging field of atomtronics. The chapter is intended as a complete guide to the experimentalist for understanding, selecting, and implementing the most appropriate optical trapping technology for a given application. After introducing the basic theory of optical trapping and image formation, we describe each of the above technologies in detail, providing a guide to the fundamental operation of optical deflectors, digital micromirror devices, and liquid crystal spatial light modulators. We also describe the capabilities of these technologies for manipulation of trapped ultracold atoms, where the potential is dynamically modified to enable experiments, and where time-averaged potentials can realise more complex traps. The key considerations when implementing time-averaged traps are described.

cond-mat.quant-gas↗

arXiv2020

Turbulent relaxation to equilibrium in a two-dimensional quantum vortex gas

We experimentally study emergence of microcanonical equilibrium states in the turbulent relaxation dynamics of a two-dimensional chiral vortex gas. Same-sign vortices are injected into a quasi-two-dimensional disk-shaped atomic Bose-Einstein condensate using a range of mechanical stirring protocols. The resulting long-time vortex distributions are found to be in excellent agreement with the meanfield Poisson-Boltzmann equation for the system describing the microcanonical ensemble at fixed energy $\cal{H}$ and angular momentum $\cal{M}$. The equilibrium states are characterized by the corresponding thermodynamic variables of inverse temperature $\hat{\beta}$ and rotation frequency $\hat{\omega}$. We are able to realize equilibria spanning the full phase diagram of the vortex gas, including on-axis states near zero-temperature, infinite temperature, and negative absolute temperatures. At sufficiently high energies the system exhibits a symmetry-breaking transition, resulting in an off-axis equilibrium phase at negative absolute temperature that no longer shares the symmetry of the container. We introduce a point-vortex model with phenomenological damping and noise that is able to quantitatively reproduce the equilibration dynamics.

cond-mat.quant-gas↗

arXiv2020

Use of Machine Learning and Artificial Intelligence to predict SARS-CoV-2 infection from Full Blood Counts in a population

Since December 2019 the novel coronavirus SARS-CoV-2 has been identified as the cause of the pandemic COVID-19. Early symptoms overlap with other common conditions such as common cold and Influenza, making early screening and diagnosis are crucial goals for health practitioners. The aim of the study was to use machine learning (ML), an artificial neural network (ANN) and a simple statistical test to identify SARS-CoV-2 positive patients from full blood counts without knowledge of symptoms or history of the individuals. The dataset included in the analysis and training contains anonymized full blood counts results from patients seen at the Hospital Israelita Albert Einstein, at S\~ao Paulo, Brazil, and who had samples collected to perform the SARS-CoV-2 rt-PCR test during a visit to the hospital. Patient data was anonymised by the hospital, clinical data was standardized to have a mean of zero and a unit standard deviation. This data was made public with the aim to allow researchers to develop ways to enable the hospital to rapidly predict and potentially identify SARS-CoV-2 positive patients. We find that with full blood counts random forest, shallow learning and a flexible ANN model predict SARS-CoV-2 patients with high accuracy between populations on regular wards (AUC = 94-95%) and those not admitted to hospital or in the community (AUC=80-86%). Here, AUC is the Area Under the receiver operating characteristics Curve and a measure for model performance. Moreover, a simple linear combination of 4 blood counts can be used to have an AUC of 85% for patients within the community. The normalised data of different blood parameters from SARS-CoV-2 positive patients exhibit a decrease in platelets, leukocytes, eosinophils, basophils and lymphocytes, and an increase in monocytes.

stat.AP↗

arXiv2020

Probing short-range correlations in the deuteron via incoherent diffractive $J/\psi$ production with spectator tagging at the EIC

Understanding the role of Quantum Chromodynamics in generating nuclear forces is important for uncovering the mechanism of short-ranged nuclear interactions and their manifestation in short range correlations (SRC). The future Electron-Ion-Collider (EIC) at Brookhaven National Laboratory in the US will provide an unprecedented opportunity to systematically investigate the underlying physics of SRC for energies and kinematic regions that are otherwise impossible to reach. We study SRCs in electron-deuteron scattering events using the Monte Carlo event generator BeAGLE. Specifically, we investigate the sensitivity of observables to high internal nucleon momentum in incoherent diffractive $J/\psi$ vector meson production. In a plane wave impulse approximation, the initial state deuteron wavefunction can be accessed directly from the four-momentum of the spectator nucleon. We use realistic physics simulations and far-forward detector simulations of the EIC to fully reveal the physics potential of this exclusive process. In particular, we provide the luminosity and detector requirements necessary to study SRCs in the deuteron at an EIC.

nucl-ex↗

arXiv2019

Quantitative acoustic models for superfluid circuits

We experimentally realize a highly tunable superfluid oscillator circuit in a quantum gas of ultracold atoms and develop and verify a simple lumped-element description of this circuit. At low oscillator currents, we demonstrate that the circuit is accurately described as a Helmholtz resonator, a fundamental element of acoustic circuits. At larger currents, the breakdown of the Helmholtz regime is heralded by a turbulent shedding of vortices and density waves. Although a simple phase-slip model offers qualitative insights into the circuit's resistive behavior, our results indicate deviations from the phase-slip model. A full understanding of the dissipation in superfluid circuits will thus require the development of empirical models of the turbulent dynamics in this system, as have been developed for classical acoustic systems.

cond-mat.quant-gas↗

arXiv2018

Giant Vortex Clusters in a Two-Dimensional Quantum Fluid

Adding energy to a system through transient stirring usually leads to more disorder. In contrast, point-like vortices in a bounded two-dimensional fluid are predicted to reorder above a certain energy, forming persistent vortex clusters. Here we realize experimentally these vortex clusters in a planar superfluid: a $^{87}$Rb Bose-Einstein condensate confined to an elliptical geometry. We demonstrate that the clusters persist for long times, maintaining the superfluid system in a high energy state far from global equilibrium. Our experiments explore a regime of vortex matter at negative absolute temperatures, and have relevance to the dynamics of topological defects, two-dimensional turbulence, and systems such as helium films, nonlinear optical materials, fermion superfluids, and quark-gluon plasmas.

cond-mat.quant-gas↗

arXiv2014

Coherent control and feedback cooling in a remotely-coupled hybrid atom-optomechanical system

Cooling to the motional ground state is an important first step in the preparation of nonclassical states of mesoscopic mechanical oscillators. Light-mediated coupling to a remote atomic ensemble has been proposed as a method to reach the ground state for low frequency oscillators. The ground state can also be reached using optical measurement followed by feedback control. Here we investigate the possibility of enhanced cooling by combining these two approaches. The combination, in general, outperforms either individual technique, though atomic ensemble-based cooling and feedback cooling each individually dominate over large regions of parameter space.

quant-ph↗

arXiv2009

Guidelines for reporting the use of gel electrophoresis in proteomics

the MIAPE Gel Electrophoresis (MIAPE-GE) guidelines specify the minimum information that should be provided when reporting the use of n-dimensional gel electrophoresis in a proteomics experiment. Developed through a joint effort between the gel-based analysis working group of the Human Proteome Organisation's Proteomics Standards Initiative (HUPO-PSI; http://www.psidev.info/) and the wider proteomics community, they constitute one part of the overall Minimum Information about a Proteomics Experiment (MIAPE) documentation system published last August in Nature Biotechnology

q-bio.GN↗

arXiv2005

A Combination Theorem for Convex Hyperbolic Manifolds, with Applications to Surfaces in 3-Manifolds

We prove the convex combination theorem for hyperbolic n-manifolds. Applications are given both in high dimensions and in 3 dimensions. One consequence is that given two geometrically finite subgroups of a discrete group of isometries of hyperbolic n-space, satisfying a natural condition on their parabolic subgroups, there are finite index subgroups which generate a subgroup that is an amalgamated free product. Constructions of infinite volume hyperbolic n-manifolds are described by gluing lower dimensional manifolds. It is shown that every slope on a cusp of a hyperbolic 3-manifold is a multiple immersed boundary slope. If a 3-manifold contains a maximal surface group not carried by an embedded surface then it contains the fundamental group of a book of I-bundles with more than two pages.

math.GT↗

arXiv2000

Cluster Computing: A High-Performance Contender

When you first heard people speak of Piles of PCs, the first thing that came to mind may have been a cluttered computer room with processors, monitors, and snarls of cables all around. Collections of computers have undoubtedly become more sophisticated than in the early days of shared drives and modem connections. No matter what you call them, Clusters of Workstations (COW), Networks of Workstations (NOW), Workstation Clusters (WCs), Clusters of PCs (CoPs), clusters of computers are now filling the processing niche once occupied by more powerful stand-alone machines. This article discusses the need for cluster computing technology, Technologies, Components, and Applications, Supercluster Systems and Issues, The Need for a New Task Force, and Cluster Computing Educational Resources.

cs.DC↗

arXiv2000

Cluster Computing White Paper

Cluster computing is not a new area of computing. It is, however, evident that there is a growing interest in its usage in all areas where applications have traditionally used parallel or distributed computing platforms. The growing interest has been fuelled in part by the availability of powerful microprocessors and high-speed networks as off-the-shelf commodity components as well as in part by the rapidly maturing software components available to support high performance and high availability applications. This White Paper has been broken down into eleven sections, each of which has been put together by academics and industrial researchers who are both experts in their fields and where willing to volunteer their time and effort to put together this White Paper. The status of this paper is draft and we are at the stage of publicizing its presence and making a Request For Comments (RFC).

cs.DC↗