3,050 research outputs found
Exponential Qubit Reduction in Optimization for Financial Transaction Settlement
We extend the qubit-efficient encoding presented in [Tan et al., Quantum 5,
454 (2021)] and apply it to instances of the financial transaction settlement
problem constructed from data provided by a regulated financial exchange. Our
methods are directly applicable to any QUBO problem with linear inequality
constraints. Our extension of previously proposed methods consists of a
simplification in varying the number of qubits used to encode correlations as
well as a new class of variational circuits which incorporate symmetries,
thereby reducing sampling overhead, improving numerical stability and
recovering the expression of the cost objective as a Hermitian observable. We
also propose optimality-preserving methods to reduce variance in real-world
data and substitute continuous slack variables. We benchmark our methods
against standard QAOA for problems consisting of 16 transactions and obtain
competitive results. Our newly proposed variational ansatz performs best
overall. We demonstrate tackling problems with 128 transactions on real quantum
hardware, exceeding previous results bounded by NISQ hardware by almost two
orders of magnitude.Comment: 16 pages, 8 figure
Location Dependent Dirichlet Processes
Dirichlet processes (DP) are widely applied in Bayesian nonparametric
modeling. However, in their basic form they do not directly integrate
dependency information among data arising from space and time. In this paper,
we propose location dependent Dirichlet processes (LDDP) which incorporate
nonparametric Gaussian processes in the DP modeling framework to model such
dependencies. We develop the LDDP in the context of mixture modeling, and
develop a mean field variational inference algorithm for this mixture model.
The effectiveness of the proposed modeling framework is shown on an image
segmentation task
Patient experiences of receiving arthroscopic surgery or personalised hip therapy for femoroacetabular impingement in the context of the UK fashion study:a qualitative study
UK FASHIoN was a multicentre randomised controlled trial comparing hip arthroscopic surgery (HA) with personalised hip therapy (PHT, physiotherapist-led conservative care), for patients with hip pain attributed to femoroacetabular impingement (FAI) syndrome. Our aim was to describe the treatment and trial participation experiences of patients, to contextualise the trial results and offer further information to assist treatment decision-making in FAI. We conducted in-depth semi-structured telephone interviews with a purposive sample of trial participants from each of the trial arms. They were interviewed after they received treatment and completed their first year of trial participation. Thematic analysis and constant comparison analytical approaches were used to identify themes of patient treatment experiences during the trial. Forty trial participants were interviewed in this qualitative study. Their baseline characteristics were similar to those in the main trial sample. On average, their hip-related quality of life (iHOT-33 scores) at 12 months follow-up were lower than average for all trial participants, indicating poorer hip-related quality of life as a consequence of theoretical sampling. Patient experiences occurred in five patient groups: those who felt their symptoms improved with hip arthroscopy, or with personal hip therapy, patients who felt their hip symptoms did not change with PHT but did not want HA, patients who decided to change from PHT to HA and a group who experienced serious complications after HA. Interviewees mostly described a trouble-free, enriching and altruistic trial participation experience, although most participants expected more clinical follow-up at the end of the trial. Both HA and PHT were experienced as beneficial by participants in the trial. Treatment success appeared to depend partly on patients' prior own expectations as well as their outcomes, and future research is needed to explore this further. Findings from this study can be combined with the primary results to inform future FAI patients
Thermodynamics of a Trapped Bose-Fermi Mixture
By using the Hartree-Fock-Bogoliubov equations within the Popov
approximation, we investigate the thermodynamic properties of a dilute binary
Bose-Fermi mixture confined in an isotropic harmonic trap. For mixtures with an
attractive Bose-Fermi interaction we find a sizable enhancement of the
condensate fraction and of the critical temperature of Bose-Einstein
condensation with respect to the predictions for a pure interacting Bose gas.
Conversely, the influence of the repulsive Bose-Fermi interaction is less
pronounced. The possible relevance of our results in current experiments on
trapped {\rm K} mixtures is discussed.Comment: 5 pages + 4 figures; minor changes, final version to appear in Phys.
Rev. A; the extension work on the finite-temperature low-lying excitations
can be found in cond-mat/030763
Density profiles and density oscillations of an interacting three-component normal Fermi gas
We use a semiclassical approximation to investigate density variations and
dipole oscillations of an interacting three-component normal Fermi gas in a
harmonic trap. We consider both attractive and repulsive interactions between
different pairs of fermions and study the effect of population imbalance on
densities. We find that the density profiles significantly deviate from those
of non-interacting profiles and extremely sensitive to interactions and
population imbalance. Unlike for a two-component Fermi system, we find density
imbalance even for balanced populations. For some range of parameters, one
component completely repels from the trap center giving rise a donut shape
density profile. Further, we find that the in-phase dipole oscillation
frequency is consistent with Kohn's theorem and other two dipole mode
frequencies are strongly effected by the interactions and the number of atoms
in the harmonic trap.Comment: Total seven pages with five figures. Published versio
Variational theory of two-fluid hydrodynamic modes at unitarity
We present the results of a variational calculation of the frequencies of the
low-lying Landau two-fluid hydrodynamic modes in a trapped Fermi superfluid gas
at unitarity. Landau's two-fluid hydrodynamics is expected to be the correct
theory of Fermi superfluids at finite temperatures close to unitarity, where
strong interactions give rise to collisional hydrodynamics. Two-fluid
hydrodynamics predicts the existence of in-phase modes in which the superfluid
and normal fluid components oscillate together, as well as out-of-phase modes
where the two components move against each other. We prove that at unitarity,
the dipole and breathing in-phase modes are locally isentropic. Their
frequencies are independent of temperature and are the same above and below the
superfluid transition. The out-of-phase modes, in contrast, are strongly
dependent on temperature and hence, can be used to test the thermodynamic
properties and superfluid density of a Fermi gas at unitarity. We give
numerical results for the frequencies of these new modes as function of
temperature in an isotropic trap at unitarity.Comment: 16 pages; 5 figure
TULIP: a randomised controlled trial of surgical versus non-surgical treatment of lateral compression injuries of the pelvis with complete sacral fractures (LC1) in the non-fragility fracture patient-a feasibility study protocol
Introduction Lateral compression type 1 (LC1) pelvic fractures are the most common type of pelvic fracture. The majority of LC1 fractures are considered stable. Fractures where a complete sacral fracture is present increases the degree of potential instability and have the potential to displace over time. Non-operative management of these unstable fractures may involve restricted weight bearing and significant rehabilitation. Frequent monitoring with X-rays is also necessary for displacement of the fracture. Operative stabilisation of these fractures may be appropriate to prevent displacement of the fracture. This may allow patients to mobilise pain-free, quicker.
Methods and analysis The study is a feasibility study to inform the design of a full definitive randomised controlled trial to guide the most appropriate management of these injuries. Participants will be recruited from major trauma centres and randomly allocated to either operative or non-operative management of their injuries. A variety of outcome instruments, measuring health-related quality of life, functional outcome and pain, will be completed at several time points up to 12 months post injury. Qualitative interviews will be undertaken with participants to explore their views of the treatments under investigation and trial processes.
Eligibility and recruitment to the study will be analysed to inform the feasibility of a definitive trial. Completion rates of the measurement instruments will be assessed, as well as their sensitivity to change and the presence of floor or ceiling effects in this population, to inform the choice of the primary outcome for a definitive trial.
Ethics and dissemination Ethical approval for the study was given by the South West—Central Bristol NHS Research Ethics Committee on 2nd July 2018 (Ref; 18/SW/0135). The study will be reported in relevant specialist journals and through presentation at specialist conferences.
Trial registration number ISRCTN1064995
C-axis Raman spectra of a normal plane-chain bilayer cuprate and the pseudogap
We investigate the Raman spectra in the geometry where both incident and
scattered photon polarizations are parallel to the -direction, for a
plane-chain bilayer coupled via a single-particle tunneling . The
Raman vertex is derived in the tight-binding limit and in the absence of
Coulomb screening, the Raman intensity can be separated into intraband
() and interband () transitions. In the
small- limit, the interband part dominates and a pseudogap will appear
as it does in the conductivity. Coulomb interactions bring in a two-particle
coupling and result in the breakdown of intra- and interband separation.
Nevertheless, when is small, the Coulomb screening () has little effect on the intensity to which the unscreened
interband transitions contribute most. In general, the total Raman spectra are
strongly dependent on the magnitude of .Comment: 23 pages, 6 figures, submitted to Phys. Rev.
Fe XVII X-ray Line Ratios for Accurate Astrophysical Plasma Diagnostics
New laboratory measurements using an Electron Beam Ion Trap (EBIT) and an
x-ray microcalorimeter are presented for the n=3 to n=2 Fe XVII emission lines
in the 15 {\AA} to 17 {\AA} range, along with new theoretical predictions for a
variety of electron energy distributions. This work improves upon our earlier
work on these lines by providing measurements at more electron impact energies
(seven values from 846 to 1185 eV), performing an in situ determination of the
x-ray window transmission, taking steps to minimize the ion impurity
concentrations, correcting the electron energies for space charge shifts, and
estimating the residual electron energy uncertainties. The results for the
3C/3D and 3s/3C line ratios are generally in agreement with the closest theory
to within 10%, and in agreement with previous measurements from an independent
group to within 20%. Better consistency between the two experimental groups is
obtained at the lowest electron energies by using theory to interpolate, taking
into account the significantly different electron energy distributions.
Evidence for resonance collision effects in the spectra is discussed.
Renormalized values for the absolute cross sections of the 3C and 3D lines are
obtained by combining previously published results, and shown to be in
agreement with the predictions of converged R-matrix theory. This work
establishes consistency between results from independent laboratories and
improves the reliability of these lines for astrophysical diagnostics. Factors
that should be taken into account for accurate diagnostics are discussed,
including electron energy distribution, polarization, absorption/scattering,
and line blends.Comment: 29 pages, including 7 figure
Finite temperature effects on the collapse of trapped Bose-Fermi mixtures
By using the self-consistent Hartree-Fock-Bogoliubov-Popov theory, we present
a detailed study of the mean-field stability of spherically trapped Bose-Fermi
mixtures at finite temperature. We find that, by increasing the temperature,
the critical particle number of bosons (or fermions) and the critical
attractive Bose-Fermi scattering length increase, leading to a significant
stabilization of the mixture.Comment: 5 pages, 4 figures; minor changes, proof version, to appear in Phys.
Rev. A (Nov. 1, 2003
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