74 research outputs found
EVALUATION OF INTRAVENOUS CATHETER INSERTION SKILLS AND CONFIDENCE LEVELS OF NURSES IN THE ACUTE CARE SETTING
The use of IVs for medication administration is an essential component in healthcare and benefits the patients (Castro-Sanchez, Charani, Drumright, Sevdalis, Shah, & Holmes, 2014). Obtaining intravenous access is a specialized nursing skill that requires a combination of clinical knowledge and psychomotor coordination (Ramer, Hunt, Ortega, Knowlton, Briggs, & Hirokawa, 2016). Difficulties created by vein size, obesity, and tortuosity can make even a skilled staff member struggle which then can lead to delays in treatment (Idemoto, Rowbottom, Reynolds, & Hickman, 2014). A single phase survey was conducted in a rural southwest Missouri hospital in order to assess confidence levels in IV skills, the approximate percentage of IVs successfully started, and to examine the willingness to learn how to use an assistive device, such as an ultrasound, in order to administer difficult to start IVs. Sixty-six nurses were surveyed with a 41% response rate. Confidence levels of IV skills were high among all participants along with percentage of successful IV starts. However, the willingness to learn how to utilize an assistive device in order to start IVs was also high. The information gathered could lead to implementing ultrasound training and use for more nurses when starting difficult IVs in order to expedite medical care, improve nurses’ confidence levels with IV skills, and improve overall patient satisfaction
Entanglement entropy of composite Fermi liquid states on the lattice: In support of the Widom formula
Quantum phases characterized by surfaces of gapless excitations are known to
violate the otherwise ubiquitous boundary law of entanglement entropy in the
form of a multiplicative log correction: . Using
variational Monte Carlo, we calculate the second R\'enyi entropy for a model
wavefunction of the composite Fermi liquid (CFL) state defined on the
two-dimensional triangular lattice. By carefully studying the scaling of the
total R\'enyi entropy and, crucially, its contributions from the modulus and
sign of the wavefunction on various finite-size geometries, we argue that the
prefactor of the leading term is equivalent to that in the analogous
free fermion wavefunction. In contrast to the recent results of Shao et al.
[PRL 114, 206402 (2015)], we thus conclude that the "Widom formula" holds even
in this non-Fermi liquid CFL state. More generally, our results further
elucidate---and place on a more quantitative footing---the relationship between
nontrivial wavefunction sign structure and entanglement
scaling in such highly entangled gapless phases.Comment: 8 pages, 6 figure
Majorana lattices from the quantized Hall limit of a proximitized spin-orbit coupled electron gas
Motivated by recent experiments demonstrating intricate quantum Hall physics
on the surface of elemental bismuth, we consider proximity coupling an -wave
superconductor to a two-dimensional electron gas with strong Rashba spin-orbit
interactions in the presence of a strong perpendicular magnetic field. We focus
on the high-field limit so that the superconductivity can be treated as a
perturbation to the low-lying Landau levels. In the clean case, wherein the
superconducting order parameter takes the form of an Abrikosov vortex lattice,
we show that a lattice of hybridized Majorana modes emerges near the plateau
transition of the lowest Landau level. However, unless
magnetic-symmetry-violating perturbations are present, the system always has an
even number of chiral Majorana edge modes and thus is strictly speaking Abelian
in nature, in agreement with previous work on related setups. Interestingly,
however, a weak topological superconducting phase can very naturally be
stabilized near the plateau transition for the square vortex lattice. The
relevance of our findings to potential near-term experiments on proximitized
materials such as bismuth will be discussed.Comment: 13 pages, 9 figure
Approaching a topological phase transition in Majorana nanowires
Recent experiments have produced mounting evidence of Majorana zero modes in
nanowire-superconductor hybrids. Signatures of an expected topological phase
transition accompanying the onset of these modes nevertheless remain elusive.
We investigate a fundamental question concerning this issue: Do well-formed
Majorana modes necessarily entail a sharp phase transition in these setups?
Assuming reasonable parameters, we argue that finite-size effects can
dramatically smooth this putative transition into a crossover, even in systems
large enough to support well-localized Majorana modes. We propose overcoming
such finite-size effects by examining the behavior of low-lying excited states
through tunneling spectroscopy. In particular, the excited-state energies
exhibit characteristic field and density dependence, and scaling with system
size, that expose an approaching topological phase transition. We suggest
several experiments for extracting the predicted behavior. As a useful
byproduct, the protocols also allow one to measure the wire's spin-orbit
coupling directly in its superconducting environment.Comment: 13 pages, 8 figure
Quantum Entangled Dark Solitons Formed by Ultracold Atoms in Optical Lattices
Inspired by experiments on Bose-Einstein condensates in optical lattices, we
study the quantum evolution of dark soliton initial conditions in the context
of the Bose-Hubbard Hamiltonian. An extensive set of quantum measures is
utilized in our analysis, including von Neumann and generalized quantum
entropies, quantum depletion, and the pair correlation function. We find that
quantum effects cause the soliton to fill in. Moreover, soliton-soliton
collisions become inelastic, in strong contrast to the predictions of
mean-field theory. These features show that the lifetime and collision
properties of dark solitons in optical lattices provide clear signals of
quantum effects.Comment: 4 pages, 4 figures; version appearing in PRL, only minor changes from
v
Dephasing and leakage dynamics of noisy Majorana-based qubits: Topological versus Andreev
Topological quantum computation encodes quantum information nonlocally by nucleating non-Abelian anyons separated by distances L, typically spanning the qubit device size. This nonlocality renders topological qubits exponentially immune to dephasing from all sources of classical noise with operator support local on the scale of L. We perform detailed analytical and numerical analyses of a time-domain Ramsey-type protocol for noisy Majorana-based qubits that is designed to validate this coveted topological protection in near-term devices such as the so-called “tetron” design. By assessing dependence of dephasing times on tunable parameters, e.g., magnetic field, our proposed protocol can clearly distinguish a bona fide Majorana qubit from one constructed from semilocal Andreev bound states, which can otherwise closely mimic the true topological scenario in local probes. In addition, we analyze leakage of the qubit out of its low-energy manifold due to classical-noise-induced generation of quasiparticle excitations; leakage limits the qubit lifetime when the bulk gap collapses, and hence our protocol further reveals the onset of a topological phase transition. This experiment requires measurement of two nearby Majorana modes for both initialization and readout—achievable, for example, by tunnel coupling to a nearby quantum dot—but no further Majorana manipulations, and thus constitutes an enticing prebraiding experiment. Along the way, we address conceptual subtleties encountered when discussing dephasing and leakage in the context of Majorana qubits
Signatures of gapless fermionic spinons on a strip of the kagome Heisenberg antiferromagnet
The search for exotic quantum spin liquid states in simple yet realistic spin
models remains a central challenge in the field of frustrated quantum
magnetism. Here we consider the canonical nearest-neighbor kagome Heisenberg
antiferromagnet restricted to a quasi-1D strip consisting entirely of
corner-sharing triangles. Using large-scale density matrix renormalization
group calculations, we identify in this model an extended gapless quantum phase
characterized by central charge and power-law decaying spin and
bond-energy correlations which oscillate at tunably incommensurate wave
vectors. We argue that this intriguing spin liquid phase can be understood as a
marginal instability of a two-band spinon Fermi surface coupled to an emergent
U(1) gauge field, an interpretation which we substantiate via bosonization
analysis and Monte Carlo calculations on model Gutzwiller variational wave
functions. Our results represent one of the first numerical demonstrations of
emergent fermionic spinons in a simple SU(2) invariant nearest-neighbor
Heisenberg model beyond the strictly 1D (Bethe chain) limit.Comment: 14 pages, 12 figure
Partial breakdown of quantum thermalization in a Hubbard-like model
We study the possible breakdown of quantum thermalization in a model of
itinerant electrons on a one-dimensional chain without disorder, with both spin
and charge degrees of freedom. The eigenstates of this model exhibit peculiar
properties in the entanglement entropy, the apparent scaling of which is
modified from a "volume law" to an "area law" after performing a partial,
site-wise measurement on the system. These properties and others suggest that
this model realizes a new, non-thermal phase of matter, known as a quantum
disentangled liquid (QDL). The putative existence of this phase has striking
implications for the foundations of quantum statistical mechanics.Comment: As accepted to PR
Ising Anyons in Frustration-Free Majorana-Dimer Models
Dimer models have long been a fruitful playground for understanding
topological physics. Here we introduce a new class - termed Majorana-dimer
models - wherein bosonic dimers are decorated with pairs of Majorana modes. We
find that the simplest examples of such systems realize an intriguing,
intrinsically fermionic phase of matter that can be viewed as the product of a
chiral Ising theory, which hosts deconfined non-Abelian quasiparticles, and a
topological superconductor. While the bulk anyons are described by
a single copy of the Ising theory, the edge remains fully gapped. Consequently,
this phase can arise in exactly solvable, frustration-free models. We describe
two parent Hamiltonians: one generalizes the well-known dimer model on the
triangular lattice, while the other is most naturally understood as a model of
decorated fluctuating loops on a honeycomb lattice. Using modular
transformations, we show that the ground-state manifold of the latter model
unambiguously exhibits all properties of the
theory. We also discuss generalizations with more than one Majorana mode per
site, which realize phases related to Kitaev's 16-fold way in a similar
fashion
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