380 research outputs found
Option Pricing using Quantum Computers
We present a methodology to price options and portfolios of options on a
gate-based quantum computer using amplitude estimation, an algorithm which
provides a quadratic speedup compared to classical Monte Carlo methods. The
options that we cover include vanilla options, multi-asset options and
path-dependent options such as barrier options. We put an emphasis on the
implementation of the quantum circuits required to build the input states and
operators needed by amplitude estimation to price the different option types.
Additionally, we show simulation results to highlight how the circuits that we
implement price the different option contracts. Finally, we examine the
performance of option pricing circuits on quantum hardware using the IBM Q
Tokyo quantum device. We employ a simple, yet effective, error mitigation
scheme that allows us to significantly reduce the errors arising from noisy
two-qubit gates.Comment: Fixed a typo. This article has been accepted in Quantu
Resolving the nucleus of Centaurus A at mid-IR wavelengths
We have observed Centaurus A with the MID-infrared Interferometric instrument
(MIDI) at the Very Large Telescope Interferometer (VLTI) at resolutions of 7 -
15 mas (at 12.5 micron) and filled gaps in the (u,v) coverage in comparison to
earlier measurements. We are now able to describe the nuclear emission in terms
of geometric components and derive their parameters by fitting models to the
interferometric data. With simple geometrical models, the best fit is achieved
for an elongated disk with flat intensity profile with diameter 76 +/- 9 mas x
35 +/- 2 mas (1.41 +/- 0.17 pc x 0.65 +/- 0.03 pc) whose major axis is oriented
at a position angle (PA) of 10.1 +/- 2.2 degrees east of north. A point source
contributes 47 +/- 11 % of the nuclear emission at 12.5 micron. There is also
evidence that neither such a uniform nor a Gaussian disk are good fits to the
data. This indicates that we are resolving more complicated small-scale
structure in AGNs with MIDI, as has been seen in Seyfert galaxies previously
observed with MIDI. The PA and inferred inclination i = 62.6 +2.1/-2.6 degrees
of the dust emission are compared with observations of gas and dust at larger
scales.Comment: Accepted for the PASA special issue on Centaurus
Operationally meaningful representations of physical systems in neural networks
To make progress in science, we often build abstract representations of
physical systems that meaningfully encode information about the systems. The
representations learnt by most current machine learning techniques reflect
statistical structure present in the training data; however, these methods do
not allow us to specify explicit and operationally meaningful requirements on
the representation. Here, we present a neural network architecture based on the
notion that agents dealing with different aspects of a physical system should
be able to communicate relevant information as efficiently as possible to one
another. This produces representations that separate different parameters which
are useful for making statements about the physical system in different
experimental settings. We present examples involving both classical and quantum
physics. For instance, our architecture finds a compact representation of an
arbitrary two-qubit system that separates local parameters from parameters
describing quantum correlations. We further show that this method can be
combined with reinforcement learning to enable representation learning within
interactive scenarios where agents need to explore experimental settings to
identify relevant variables.Comment: 24 pages, 13 figure
Ammonia (J,K) = (1,1) to (4,4) and (6,6) inversion lines detected in the Seyfert 2 galaxy NGC 1068
We present the detection of the ammonia (NH3) (J,K) = (1,1) to (4,4) and
(6,6) inversion lines toward the prototypical Seyfert 2 galaxy NGC 1068, made
with the Green Bank Telescope (GBT). This is the first detection of ammonia in
a Seyfert galaxy. The ortho-to-para-NH3 abundance ratio suggests that the
molecule was formed in a warm medium of at least 20 K. For the NH3 column
density and fractional abundance, we find (1.09\pm0.23)\times10^14 cm^-2 and
(2.9\pm0.6)\times10^-8, respectively, from the inner 1.2 kpc of NGC 1068. The
kinetic temperature can be constrained to 80\pm20 K for the bulk of the
molecular gas, while some fraction has an even higher temperature of 140\pm30
K.Comment: 5 pages, 3 figures, accepted by A&
Conformation of 1,4-dihydropyridine — planar or boat-like?
AbstractThe geometry of the 1,4-dihydropyridine molecule was completely optimized employing three different ab initio basis sets (6–31 G*, 4–31 G, STO—3G). The most reliable 6–31G* basis set provides a very flat boat conformation which may easily undergo defolding to a planar ring arrangement. This result is discussed with respect to enzymatic redox cofactors and the pharmacological activity of dihydropyridine calcium antagonists
Sub-millimeter to centimeter excess emission from the Magellanic Clouds. I. Global spectral energy distribution
In order to reconstruct the global SEDs of the Magellanic Clouds over eight
decades in spectral range, we combined literature flux densities representing
the entire LMC and SMC respectively, and complemented these with maps extracted
from the WMAP and COBE databases covering the missing the 23--90 GHz (13--3.2
mm) and the poorly sampled 1.25--250 THz (240--1.25 micron). We have discovered
a pronounced excess of emission from both Magellanic Clouds, but especially the
SMC, at millimeter and sub-millimeter wavelengths. We also determined accurate
thermal radio fluxes and very low global extinctions for both LMC and SMC.
Possible explanations are briefly considered but as long as the nature of the
excess emission is unknown, the total dust masses and gas-to-dust ratios of the
Magellanic Clouds cannot reliably be determined.Comment: Accepted for publication by A&
Measuring the financial and productivity burden of paediatric hospitalisation on the wider family network
Aim: To estimate the non-medical out-of-pocket costs for families with a child in hospital. Methods: This study was a survey of 225 parents of paediatric inpatients on nine wards of an Australian public paediatric teaching hospital on two separate days. Our primary outcomes were the costs associated with: (i) time taken off work to care for the child in hospital; (ii) time off work or contributed by family and friends to care for other dependents; and (iii) travel, meals, accommodation and incidental expenses during the child's stay. Demographic data included postcode (to assess distance, socio-economic status and remoteness), child's age, ward and whether this was their child's first admission. Results: Mean patient age was 6.5 years (standard deviation 5.2). On an average per patient day basis, parents took 1.12 days off work and spent 0.61 (standard deviation 0.53) nights away from home, with 83.8% of nights away at the child's bedside. Parents spent Australian dollars (AUD)89 per day on travel and AUD36 on meals and accommodation. Total costs (including productivity costs) were AUD589 per patient day. Higher costs per patient day were correlated with living in a more remote area (0.48) and a greater travel distance to the hospital (0.41). A higher number of days off work was correlated (0.69) with number of school days missed. Conclusion: These results demonstrate the considerable time and financial resources expended by families caring for a child in hospital and are important inputs in evaluating health-care interventions that affect risk of hospitalisation and length of stay in paediatric care.Virginia Mumford, Melissa T Baysari, Djala Kalinin, Magdalena Z Raban, Cheryl McCullagh, Jonathon Karnon and Johanna I Westbroo
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Profiling complex word usage in the speech of English preschool children: frequency patterns and transparency characteristics
This corpus-based study provides a baseline of complex word usage patterns in the spontaneous speech of English preschool children to ascertain the characteristics of their derivative vocabulary before literacy development affects language skills. Frequencies of suffixed derivatives produced by (N=243) children aged 2-5 and their caregivers were extracted for 58 suffix variants, yielding 558 types from the former and 1,364 from the latter. Between the youngest and oldest groups, 11 suffix categories increased significantly in type frequency, compared with 22 in the caregiver dataset. All derivative types were classified for transparency of meaning and simplicity of form on a 5-point analysability scale. Around 59% of both the child and caregiver derivative vocabulary sets were classified as transparent regardless of age, suggesting that the potential analysability of the preschool child’s input remains surprisingly invariant over time. The study provides baseline data for future studies on the development of morphological awareness in English-speaking schoolchildren
Co-designing a dashboard of predictive analytics and decision support to drive care quality and client outcomes in aged care: a mixed-method study protocol
IntroductionThere is a clear need for improved care quality and quality monitoring in aged care. Aged care providers collect an abundance of data, yet rarely are these data integrated and transformed in real-time into actionable information to support evidence-based care, nor are they shared with older people and informal caregivers. This protocol describes the co-design and testing of a dashboard in residential aged care facilities (nursing or care homes) and community-based aged care settings (formal care provided at home or in the community). The dashboard will comprise integrated data to provide an 'at-a-glance' overview of aged care clients, indicators to identify clients at risk of fall-related hospitalisations and poor quality of life, and evidence-based decision support to minimise these risks. Longer term plans for dashboard implementation and evaluation are also outlined.MethodsThis mixed-method study will involve (1) co-designing dashboard features with aged care staff, clients, informal caregivers and general practitioners (GPs), (2) integrating aged care data silos and developing risk models, and (3) testing dashboard prototypes with users. The dashboard features will be informed by direct observations of routine work, interviews, focus groups and co-design groups with users, and a community forum. Multivariable discrete time survival models will be used to develop risk indicators, using predictors from linked historical aged care and hospital data. Dashboard prototype testing will comprise interviews, focus groups and walk-through scenarios using a think-aloud approach with staff members, clients and informal caregivers, and a GP workshop.Ethics and disseminationThis study has received ethical approval from the New South Wales (NSW) Population & Health Services Research Ethics Committee and Macquarie University's Human Research Ethics Committee. The research findings will be presented to the aged care provider who will share results with staff members, clients, residents and informal caregivers. Findings will be disseminated as peer-reviewed journal articles, policy briefs and conference presentations
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