1,009 research outputs found
Tricolored Lattice Gauge Theory with Randomness: Fault-Tolerance in Topological Color Codes
We compute the error threshold of color codes, a class of topological quantum
codes that allow a direct implementation of quantum Clifford gates, when both
qubit and measurement errors are present. By mapping the problem onto a
statistical-mechanical three-dimensional disordered Ising lattice gauge theory,
we estimate via large-scale Monte Carlo simulations that color codes are stable
against 4.5(2)% errors. Furthermore, by evaluating the skewness of the Wilson
loop distributions, we introduce a very sensitive probe to locate first-order
phase transitions in lattice gauge theories.Comment: 12 pages, 5 figures, 1 tabl
Development of practice principles for the management of ongoing suicidal ideation in young people diagnosed with major depressive disorder
Objectives:
There is a lack of clear guidance regarding the management of ongoing suicidality in young people experiencing major depressive disorder. This study utilised an expert consensus approach in identifying practice principles to complement relevant clinical guidelines for the treatment of major depressive disorder in young people. The study also sought to outline a broad treatment framework for clinical intervention with young people experiencing ongoing suicidal ideation.
Methods:
In-depth focus groups were undertaken with a specialist multidisciplinary clinical team (the Youth Mood Clinic at Orygen Youth Health Clinical Program, Melbourne) working with young people aged 15â25âyears experiencing ongoing suicidal ideation. Each focus group was audio recorded and transcribed verbatim using orthographic conventions. Principles of grounded theory and thematic analysis were used to analyse and code the resultant data.
Results:
The identified codes were subsequently synthesised into eight practice principles reflecting engagement and consistency of care, ongoing risk assessment and documentation, individualised crisis planning, engaging systems of support, engendering hopefulness, development of adaptive coping, management of acute risk, and consultation and supervision.
Conclusions:
The identified practice principles provide a broad management framework, and may assist to improve treatment consistency and clinical management of young people experiencing ongoing suicidal ideation. The practice principles may be of use to health professionals working within a team-based setting involved in the provision of care, even if peripherally, to young people with ongoing suicidal ideation. Findings address the lack of treatment consistency and shared terminology and may provide containment and guidance to multidisciplinary clinicians working with this at-risk group
Geometrical Ambiguity of Pair Statistics. I. Point Configurations
Point configurations have been widely used as model systems in condensed
matter physics, materials science and biology. Statistical descriptors such as
the -body distribution function is usually employed to characterize
the point configurations, among which the most extensively used is the pair
distribution function . An intriguing inverse problem of practical
importance that has been receiving considerable attention is the degree to
which a point configuration can be reconstructed from the pair distribution
function of a target configuration. Although it is known that the pair-distance
information contained in is in general insufficient to uniquely determine
a point configuration, this concept does not seem to be widely appreciated and
general claims of uniqueness of the reconstructions using pair information have
been made based on numerical studies. In this paper, we introduce the idea of
the distance space, called the space. The pair distances of a
specific point configuration are then represented by a single point in the
space. We derive the conditions on the pair distances that can be
associated with a point configuration, which are equivalent to the
realizability conditions of the pair distribution function . Moreover, we
derive the conditions on the pair distances that can be assembled into distinct
configurations. These conditions define a bounded region in the
space. By explicitly constructing a variety of degenerate point configurations
using the space, we show that pair information is indeed
insufficient to uniquely determine the configuration in general. We also
discuss several important problems in statistical physics based on the
space.Comment: 28 pages, 8 figure
Sliding mode control of quantum systems
This paper proposes a new robust control method for quantum systems with
uncertainties involving sliding mode control (SMC). Sliding mode control is a
widely used approach in classical control theory and industrial applications.
We show that SMC is also a useful method for robust control of quantum systems.
In this paper, we define two specific classes of sliding modes (i.e.,
eigenstates and state subspaces) and propose two novel methods combining
unitary control and periodic projective measurements for the design of quantum
sliding mode control systems. Two examples including a two-level system and a
three-level system are presented to demonstrate the proposed SMC method. One of
main features of the proposed method is that the designed control laws can
guarantee desired control performance in the presence of uncertainties in the
system Hamiltonian. This sliding mode control approach provides a useful
control theoretic tool for robust quantum information processing with
uncertainties.Comment: 18 pages, 4 figure
Boundary lubrication with a glassy interface
Recently introduced constitutive equations for the rheology of dense,
disordered materials are investigated in the context of stick-slip experiments
in boundary lubrication. The model is based on a generalization of the shear
transformation zone (STZ) theory, in which plastic deformation is represented
by a population of mesoscopic regions which may undergo non affine deformations
in response to stress. The generalization we study phenomenologically
incorporates the effects of aging and glassy relaxation. Under experimental
conditions associated with typical transitions from stick-slip to steady
sliding and stop start tests, these effects can be dominant, although the full
STZ description is necessary to account for more complex, chaotic transitions
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Innovating Interdisciplinarity in Higher Education: Exploring the Impact of a Grassroots Community of Practice
Skills in interdisciplinary collaboration are required to address many complex problems facing society. As such, interdisciplinarity is a critical competency for students to develop. However, teachersâ effectiveness in teaching interdisciplinarity is often hindered by silo structures within university faculties. To address this in the Experts in Teamwork (EiT) programme, a MSc in a Norwegian university that develops studentsâ interdisciplinary teamwork skills through projects that address real-world challenges, a community of practice (CoP) evolved among teachers from different EiT classes. Over 20 months, CoP members participated in digital and in-person discussions, lecture exchanges, student and professional conferences, and co-evaluation of student work, with an aim of better understanding interdisciplinarity and approaches for teaching it to students. The success of the CoP in achieving these aims was evaluated through a series of focus groups consisting of members of the CoP. The CoP achieved some success in fostering pedagogical conversations that were transformative for participantsâ understanding of interdisciplinarity in their practice. Participants reported that CoP participation influenced their interactions with students, ultimately helping students to develop a better understanding of interdisciplinarity. However, participants reported limitations in the CoP as a professional development resource, citing its newness and the required time commitment. Participants felt that these issues could be addressed via greater institutional support
In-plane polarized collective modes in detwinned YBaCuO observed by spectral ellipsometry
The in-plane dielectric response of detwinned YBaCuO has
been studied by far-infared ellipsometry. A surprisingly lare number of
in-plane polarized modes are observed. Some of them correspond to pure phonon
modes. Others posses a large electronic contribution which strongly increases
in the superconducting state. The free carrier response and the collective
modes exhibit a pronounced a-b anisotropy. We discuss our results in terms of a
CDW state in the 1-d CuO chains and induced charge density fluctuations within
the 2-d CuO planes
Cyclotron resonance in the layered perovskite superconductor Sr2RuO4
We report a detailed study of the magnetic-field-orientation dependence of
the millimetre-wave magnetoconductivity of the superconductor Sr2RuO4 We find
two harmonic series of cyclotron resonances. We assign the first, corresponding
to a quasiparticle mass of , where is the
free-electron mass, to the Fermi-surface section. We assign the second
series, which contains only odd harmonics, to cyclotron resonance of the
Fermi-surface section, yielding a quasiparticle mass of . A third, single cyclotron resonance, corresponding to a
quasiparticle mass of , is attributed to the
Fermi-surface section. In addition, we find a very strong absorption mode in
the presence of a magnetic field component parallel to the
quasi-two-dimensional planes of the sample. Its dependence on the orientation
of the magnetic field cannot be described in the context of conventional
cyclotron resonance, and the origin of this mode is not yet clear.Comment: Submitted to J. Phys. Cond. Ma
Counterion adsorption on flexible polyelectrolytes: comparison of theories
Counterion adsorption on a flexible polyelectrolyte chain in a spherical
cavity is considered by taking a "permuted" charge distribution on the chain so
that the "adsorbed" counterions are allowed to move along the backbone. We
compute the degree of ionization by using self-consistent field theory (SCFT)
and compare with the previously developed variational theory. Analysis of
various contributions to the free energy in both theories reveals that the
equilibrium degree of ionization is attained mainly as an interplay of the
adsorption energy of counterions on the backbone, the translational entropy of
the small ions, and their correlated density fluctuations. Degree of ionization
computed from SCFT is significantly lower than that from the variational
formalism. The difference is entirely due to the density fluctuations of the
small ions in the system, which are accounted for in the variational procedure.
When these fluctuations are deliberately suppressed in the truncated
variational procedure, there emerges a remarkable quantitative agreement in the
various contributing factors to the equilibrium degree of ionization, in spite
of the fundamental differences in the approximations and computational
procedures used in these two schemes. Nevertheless, since the significant
effects from density fluctuations of small ions are not captured by the SCFT,
and due to the close agreement between SCFT and the other contributing factors
in the more transparent variational procedure, the latter is a better
computational tool for obtaining the degree of ionization
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