1,878 research outputs found
General error estimate for adiabatic quantum computing
Most investigations devoted to the conditions for adiabatic quantum computing
are based on the first-order correction . However, it is
demonstrated that this first-order correction does not yield a good estimate
for the computational error. Therefore, a more general criterion is proposed,
which includes higher-order corrections as well and shows that the
computational error can be made exponentially small -- which facilitates
significantly shorter evolution times than the above first-order estimate in
certain situations. Based on this criterion and rather general arguments and
assumptions, it can be demonstrated that a run-time of order of the inverse
minimum energy gap is sufficient and necessary, i.e.,
T=\ord(\Delta E_{\rm min}^{-1}). For some examples, these analytical
investigations are confirmed by numerical simulations. PACS: 03.67.Lx,
03.67.-a.Comment: 8 pages, 6 figures, several modification
Spin-1/2 particles moving on a 2D lattice with nearest-neighbor interactions can realize an autonomous quantum computer
What is the simplest Hamiltonian which can implement quantum computation
without requiring any control operations during the computation process? In a
previous paper we have constructed a 10-local finite-range interaction among
qubits on a 2D lattice having this property. Here we show that
pair-interactions among qutrits on a 2D lattice are sufficient, too, and can
also implement an ergodic computer where the result can be read out from the
time average state after some post-selection with high success probability.
Two of the 3 qutrit states are given by the two levels of a spin-1/2 particle
located at a specific lattice site, the third state is its absence. Usual
hopping terms together with an attractive force among adjacent particles induce
a coupled quantum walk where the particle spins are subjected to spatially
inhomogeneous interactions implementing holonomic quantum computing. The
holonomic method ensures that the implemented circuit does not depend on the
time needed for the walk.
Even though the implementation of the required type of spin-spin interactions
is currently unclear, the model shows that quite simple Hamiltonians are
powerful enough to allow for universal quantum computing in a closed physical
system.Comment: More detailed explanations including description of a programmable
version. 44 pages, 12 figures, latex. To appear in PR
Electron spin polarization in field emission from nickel: effects of surface adsorbates
Müller N. Electron spin polarization in field emission from nickel: effects of surface adsorbates. Physics Letters, A. 1975;54(5):415-416.Spin polarization of electrons field emitted from certain faces of more or less clean nickel is observed. The preferential spin direction is proved to depend on the crystal direction and on the adsorbate contamination of the face
Metallicity, temperature, and gravity scales of M subdwarfs
The aim of the project is to define a metallicity/gravity/temperature scale
vs spectral types for metal-poor M dwarfs.
We obtained intermediate-resolution ultraviolet (R~3300), optical (R~5400),
and near-infrared (R~3900) spectra of 43 M subdwarfs (sdM), extreme subdwarfs
(esdM), and ultra-subdwarfs (usdM) with the X-shooter spectrograph on the
European Southern Observatory Very Large Telescope. We compared our atlas of
spectra to the latest BT-Settl synthetic spectral energy distribution over a
wide range of metallicities, gravities, and effective temperatures to infer the
physical properties for the whole M dwarf sequence (M0--M9.5) at sub-solar
metallicities and constrain the latest state-of-the-art atmospheric models.
The BT-Settl models reproduce well the observed spectra across the 450-2500
nm wavelength range except for a few regions. We find that the best fits are
obtained for gravities of log(g) = 5.0-5.5 dex for the three metal classes. We
infer metallicities of [Fe/H] = -0.5, -1.5, and -2.0+/-0.5 dex and effective
temperatures of 3700-2600 K, 3800-2900 K, and 3700-2900 K for subdwarfs,
extreme subdwarfs, and ultra-subdwarfs, respectively. Metal-poor M dwarfs tend
to be warmer by about 200+/-100 K and exhibit higher gravity than their
solar-metallicity counterparts. We derive abundances of several elements (Fe,
Na, K, Ca, Ti) for our sample but cannot describe their atmospheres with a
single metallicity parameter. Our metallicity scale expands the current scales
available for midly metal-poor planet-host low-mass stars. Our compendium of
moderate-resolution spectra covering the 0.45--2.5 micron range represents an
important legacy value for large-scale surveys and space missions to come.Comment: 31 pages, 4 pages, 4 tables + 1 appendix with 12 figures and 5
tables. Accepted for publication in A&A. Version prior to language editio
Near-Infrared water lines in V838 Monocerotis
V838 Monocerotis had an intriguing, nova-like outburst in January 2002 which
has subsequently led to several studies of the object. It is now recognized
that the outburst of V838 Mon and its evolution are different from that of a
classical nova or other classes of well-known eruptive variables. V838 Mon,
along with two other objects that have analogous properties, appears to
comprise a new class of eruptive variables. There are limited infrared studies
of V838 Mon. Here, we present near-infrared H band (1.5 - 1.75micron) spectra
of V838 Mon from late 2002 to the end of 2004. The principal, new result from
our work is the detection of several, rotation-vibration lines of water in the
H band spectra. The observed water lines have been modeled to first establish
that they are indeed due to water. Subsequently the temperature and column
densities of the absorbing material, from where the water absorption features
originate, are derived. From our analysis, we find that the water features
arise from a cool ~750-900 K region around V838 Mon which appears to be
gradually cooling with time.Comment: 11 pages, 2 figures. Accepted in Ap.J Letter
Recommended from our members
Children and Their Parents’ Assessment of Postoperative Surgical Pain: Agree or Disagree?
Objective The purpose of this study is to compare postoperative pain scores between children undergoing tonsillectomy and adenoidectomy (T&A) surgery and their parents, identify potential predictors for this disagreement, and determine possible impact on analgesic administration. Methods This is a prospective longitudinal study conducted with children undergoing outpatient T&A in 4 major tertiary hospitals and their parents. Children and their parents were enrolled prior to surgery and completed baseline psychological instruments assessing parental anxiety (STAI), parental coping style (MBSS), child temperament (EAS) and parental medication administration attitude questionnaire (MAQ). Postoperatively, parents and children completed at-home pain severity ratings (Faces Pain Scale-Revised, children; Numeric Rating Scale, parents) on postoperative recovery days 1, 2, and 3, reflecting an overall pain level for the past 24 h. Parents also completed a log of analgesic administration. Based on postoperative pain scores, parent-child dyads were classified as overestimators (i.e., parents rated their child\u27s pain higher than children rated their own pain), in agreement (i.e., rating in agreement), or underestimators (i.e., parents rated their child\u27s pain lower than children rated their own pain). Results A significant proportion of parent-child pairs disagreed on pain ratings on postoperative days 1–3 (30.05%–35.95%). Of those pairs in disagreement, the majority of parents overestimated their child\u27s pain on all three postoperative days, specifically such that a total of 24–26% parents overestimated their child\u27s pain on postoperative days 1, 2, and 3. Repeated measures ANOVA demonstrated that parents in the overestimator group administered higher, though still within safe limits, amounts of ibuprofen and oxycodone (mg/day) than did the underestimator or agreement groups. Multiple regression models showed hospital site as the only independent predictor for postoperative pain rating disagreement between children and parents. Conclusions Since parents overestimate their child\u27s postoperative pain and may administer more analgesics to their child, it is essential to develop a standardized method of child pain assessment and a tailored recommended postoperative analgesic regimen amongst medical providers for children undergoing T&A
Functional consequences of seven novel mutations in the CYP11B1 Gene: four mutations associated with nonclassic and three mutations causing classic 11 -Hydroxylase Deficiency
Context: Steroid 11β-hydroxylase (CYP11B1) deficiency (11OHD) is the second most common form of congenital adrenal hyperplasia (CAH). Cases of nonclassic 11OHD are rare compared with the incidence of nonclassic 21-hydroxylase deficiency.
Objective: The aim of the study was to analyze the functional consequences of seven novel CYP11B1 mutations (p.M88I, p.W116G, p.P159L, p.A165D, p.K254_A259del, p.R366C, p.T401A) found in three patients with classic 11OHD, two patients with nonclassic 11OHD, and three heterozygous carriers for CYP11B1 mutations.
Methods: We conducted functional studies employing a COS7 cell in vitro expression system comparing wild-type (WT) and mutant CYP11B1 activity. Mutants were examined in a computational three-dimensional model of the CYP11B1 protein.
Results: All mutations (p.W116G, p.A165D, p.K254_A259del) found in patients with classic 11OHD have absent or very little 11β-hydroxylase activity relative to WT. The mutations detected in patients with nonclassic 11OHD showed partial functional impairment, with one patient being homozygous (p.P159L; 25% of WT) and the other patient compound heterozygous for a novel mild p.M88I (40% of WT) and the known severe p.R383Q mutation. The two mutations detected in heterozygous carriers (p.R366C, p.T401A) also reduced CYP11B1 activity by 23 to 37%, respectively.
Conclusion: Functional analysis results allow for the classification of novel CYP11B1 mutations as causative for classic and nonclassic 11OHD, respectively. Four partially inactivating mutations are predicted to result in nonclassic 11OHD. These findings double the number of mild CYP11B1 mutations previously described as associated with mild 11OHD. Our data are important to predict phenotypic expression and provide important information for clinical and genetic counseling i
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