arXiv subjects

A. Scott

Publications and source records attributed to A. Scott.

10 recordsLinked to original sources

arXiv2023

Mid-circuit measurements on a single species neutral alkali atom quantum processor

We demonstrate mid-circuit measurements in a neutral atom array by shelving data qubits in protected hyperfine-Zeeman sub-states while non-destructively measuring an ancilla qubit. Measurement fidelity was enhanced using microwave repumping of the ancilla during the measurement. The coherence of the shelved data qubits was extended during the ancilla readout with dynamical decoupling pulses, after which the data qubits are returned to mf = 0 computational basis states. We demonstrate that the quantum state of the data qubits is well preserved up to a constant phase shift with a state preparation and measurement (SPAM) corrected process fidelity of F = 97.0(5)%. The measurement fidelity on the ancilla qubit after correction for state preparation errors is F = 94.9(8)% and F = 95.3(1.1)% for |0> and |1> qubit states, respectively. We discuss extending this technique to repetitive quantum error correction using quadrupole recooling and microwave-based quantum state resetting.

quant-ph↗

arXiv2021

Trust and Safety

Robotics in Australia have a long history of conforming with safety standards and risk managed practices. This chapter articulates the current state of trust and safety in robotics including society's expectations, safety management systems and system safety as well as emerging issues and methods for ensuring safety in increasingly autonomous robotics. The future of trust and safety will combine standards with iterative, adaptive and responsive regulatory and assurance methods for diverse applications of robotics, autonomous systems and artificial intelligence (RAS-AI). Robotics will need novel technical and social approaches to achieve assurance, particularly for game-changing innovations. The ability for users to easily update algorithms and software, which alters the performance of a system, implies that traditional machine assurance performed prior to deployment or sale, will no longer be viable. Moreover, the high frequency of updates implies that traditional certification that requires substantial time will no longer be practical. To alleviate these difficulties, automation of assurance will likely be needed; something like 'ASsurance-as-a-Service' (ASaaS), where APIs constantly ping RAS-AI to ensure abidance with various rules, frameworks and behavioural expectations. There are exceptions to this, such as in contested or communications denied environments, or in underground or undersea mining; and these systems need their own risk assessments and limitations imposed. Indeed, self-monitors are already operating within some systems. To ensure safe operations of future robotics systems, Australia needs to invest in RAS-AI assurance research, stakeholder engagement and continued development and refinement of robust frameworks, methods, guidelines and policy in order to educate and prepare its technology developers, certifiers, and general population.

cs.RO↗

arXiv2021

The DECam Local Volume Exploration Survey: Overview and First Data Release

The DECam Local Volume Exploration survey (DELVE) is a 126-night survey program on the 4-m Blanco Telescope at the Cerro Tololo Inter-American Observatory in Chile. DELVE seeks to understand the characteristics of faint satellite galaxies and other resolved stellar substructures over a range of environments in the Local Volume. DELVE will combine new DECam observations with archival DECam data to cover ~15000 deg$^2$ of high-Galactic-latitude (|b| > 10 deg) southern sky to a 5$\sigma$ depth of g,r,i,z ~ 23.5 mag. In addition, DELVE will cover a region of ~2200 deg$^2$ around the Magellanic Clouds to a depth of g,r,i ~ 24.5 mag and an area of ~135 deg$^2$ around four Magellanic analogs to a depth of g,i ~ 25.5 mag. Here, we present an overview of the DELVE program and progress to date. We also summarize the first DELVE public data release (DELVE DR1), which provides point-source and automatic aperture photometry for ~520 million astronomical sources covering ~5000 deg$^2$ of the southern sky to a 5$\sigma$ point-source depth of g=24.3, r=23.9, i=23.3, and z=22.8 mag. DELVE DR1 is publicly available via the NOIRLab Astro Data Lab science platform.

astro-ph.GA↗

arXiv2021

Quantifying residual stress in Helium implanted surfaces and its implication for blistering

Helium implantation in surfaces is of interest for plasma facing materials and other nuclear applications. Vanadium as both a representative bcc material and a material relevant for fusion applications is implanted using a Helium ion beam microscope, and the resulting swelling and nanomechanical properties are quantified. These values are put in correlation to data obtained from micro residual stress measurements using a focused ion beam based ring-core technique. We found that the swelling measured is similar to literature values. Further we are able to measure the surface stress caused by the implantation and find it approaches the yield strength of the material at blistering doses. The simple calculations performed in the present work, along with several geometrical considerations deduced from experimental results confirm the driving force for blister formation comes from bulging resulting mainly from gas pressure buildup, rather than solely stress induced buckling.

cond-mat.mtrl-sci↗

arXiv2000

Investigation of the Exclusive 3He(e,e'pp)n Reaction

Cross sections for the 3He(e,e'pp)n reaction were measured over a wide range of energy and three- momentum transfer. At a momentum transfer q=375 MeV/c, data were taken at transferred energies omega ranging from 170 to 290 MeV. At omega=220 MeV, measurements were performed at three q values (305, 375, and 445 MeV/c). The results are presented as a function of the neutron momentum in the final-state, as a function of the energy and momentum transfer, and as a function of the relative momentum of the two-proton system. The data at neutron momenta below 100 MeV/c, obtained for two values of the momentum transfer at omega=220 MeV, are well described by the results of continuum-Faddeev calculations. These calculations indicate that the cross section in this domain is dominated by direct two-proton emission induced by a one-body hadronic current. Cross section distributions determined as a function of the relative momentum of the two protons are fairly well reproduced by continuum-Faddeev calculations based on various realistic nucleon-nucleon potential models. At higher neutron momentum and at higher energy transfer, deviations between data and calculations are observed that may be due to contributions of isobar currents.

nucl-ex↗

arXiv1999

Investigation of the Exclusive 3He(e,e'pp) Reaction

Cross sections for the 3He(e,e'pp)n reaction were measured at an energy transfer of 220 MeV and three-momentum transfers q of 305, 375, and 445 MeV/c. Results are presented as a function of q and the final-state neutron momentum for slices in specific kinematic variables. At low neutron momenta, comparison of the data to results of continuum Faddeev calculations performed with the Bonn-B nucleon-nucleon potential indicates a dominant role for two-proton knockout induced by a one-body hadronic current.

nucl-ex↗

arXiv1998

Neutrons from multiplicity-selected La-La and Nb-Nb collisions at 400A MeV and La-La collisions at 250A MeV

Triple-differential cross sections for neutrons from high-multiplicity La-La collisions at 250 and 400 MeV per nucleon and Nb-Nb collisions at 400 MeV per nucleon were measured at several polar angles as a function of the azimuthal angle with respect to the reaction plane of the collision. The reaction plane was determined by a transverse-velocity method with the capability of identifying charged-particles with Z=1, Z=2, and Z > 2. The flow of neutrons was extracted from the slope at mid-rapidity of the curve of the average in-plane momentum vs the center-of-mass rapidity. The squeeze-out of the participant neutrons was observed in a direction normal to the reaction plane in the normalized momentum coordinates in the center-of-mass system. Experimental results of the neutron squeeze-out were compared with BUU calculations. The polar-angle dependence of the maximum azimuthal anisotropy ratio $r(θ)$ was found to be insensitive to the mass of the colliding nuclei and the beam energy. Comparison of the observed polar-angle dependence of the maximum azimuthal anisotropy ratio $r(θ)$ with BUU calculations for free neutrons revealed that $r(θ)$ is insensitive also to the incompressibility modulus in the nuclear equation of state.

nucl-ex↗

arXiv1998

Lambda Hyperons in 2 A*GeV Ni + Cu Collisions

A sample of Lambda's produced in 2 A*GeV Ni + Cu collisions has been obtained with the EOS Time Projection Chamber at the Bevalac. Low background in the invariant mass distribution allows for the unambiguous demonstration of Lambda directed flow. The transverse mass spectrum at mid-rapidity has the characteristic shoulder-arm shape of particles undergoing radial transverse expansion. A linear dependence of Lambda multiplicity on impact parameter is observed, from which a total Lambda + Sigma^0 production cross section of $112 +/- 24 mb is deduced. Detailed comparisons with the ARC and RVUU models are made.

nucl-ex↗

arXiv1996

The Evolution of Nuclear Multifragmentation in the Temperature-Density Plane

The mean transverse kinetic energies of the fragments formed in the interaction of 1 A GeV Au+C have been determined. An energy balance argument indicates the presence of a collective energy which increases in magnitude with increasing multiplicity and accounts for nearly half of the measured mean transverse kinetic energy. The radial flow velocity associated with the collective energy yields estimates for the time required to expand to the freeze-out volume. Isentropic trajectories in the temperature-density plane are shown for the expansion and indicate that the system goes through the critical region at the same multiplicities as deduced from a statistical analysis. Here, the expansion time is approximately 70 fm/c.

nucl-ex↗

arXiv1995

Radial Flow in Au+Au Collisions at E=0.25-1.15 A GeV

A systematic study of energy spectra for light particles emitted at midrapidity from Au+Au collisions at E=0.25-1.15 A GeV reveals a significant non-thermal component consistent with a collective radial flow. This component is evaluated as a function of bombarding energy and event centrality. Comparisons to Quantum Molecular Dynamics (QMD) and Boltzmann-Uehling-Uhlenbeck (BUU) models are made for different equations of state.

nucl-ex↗