833 research outputs found
Physical Optimization of Quantum Error Correction Circuits
Quantum error correcting codes have been developed to protect a quantum
computer from decoherence due to a noisy environment. In this paper, we present
two methods for optimizing the physical implementation of such error correction
schemes. First, we discuss an optimal quantum circuit implementation of the
smallest error-correcting code (the three bit code). Quantum circuits are
physically implemented by serial pulses, i.e. by switching on and off external
parameters in the Hamiltonian one after another. In contrast to this, we
introduce a new parallel switching method that allows faster gate operation by
switching all external parameters simultaneously. These two methods are applied
to electron spins in coupled quantum dots subject to a Heisenberg coupling
H=J(t) S_1*S_2 which can generate the universal quantum gate
`square-root-of-swap'. Using parallel pulses, the encoding for three-bit
quantum error correction in a Heisenberg system can be accelerated by a factor
of about two. We point out that parallel switching has potential applications
for arbitrary quantum computer architectures.Comment: 13 pages, 6 figure
Neurological Dysfunction in Coeliac Disease and Non-Coeliac Gluten Sensitivity
OBJECTIVES: Non-coeliac gluten sensitivity (NCGS) refers to patients with primarily gastrointestinal symptoms
without enteropathy that symptomatically benefi t from gluten-free diet (GFD). Little is known about
its pathophysiology, propensity to neurological manifestations, and if these differ from patients with
coeliac disease (CD). We investigated the clinical and immunological characteristics of patients
presenting with neurological manifestations with CD and those with NCGS.
METHODS: We compared clinical, neurophysiological, and imaging data of patients with CD and NCGS
presenting with neurological dysfunction assessed and followed up regularly over a period of
20 years.
RESULTS: Out of 700 patients, 562 were included. Exclusion criteria included no bowel biopsy to confi rm
CD, no HLA type available, and failure to adhere to GFD. All patients presented with neurological
dysfunction and had circulating anti-gliadin antibodies. Out of 562 patients, 228 (41%) had
evidence of enteropathy (Group 1, CD) and 334 (59%) did not (Group 2, NCGS). The most common
neurological manifestations were cerebellar ataxia, peripheral neuropathy, and encephalopathy. There
was a greater proportion of patients with encephalopathy in Group 1 and with a greater proportion
of neuropathy in Group 2. The severity of ataxia did not differ between the two groups. Patients in
Group 1 had more severe neuropathy. All patients from both groups responded to gluten-free diet.
Anti-tissue transglutaminase (TG2) antibodies were found in 91% of patients in Group 1 and in
29% of patients in Group 2. Comparison between those patients in Group 2 with HLA-DQ2/DQ8 and
those without as well as those with positive TG2 compared with those with negative TG2 antibodies
identifi ed no differences within these subgroups. Serological positivity for TG6 antibodies was similar
in the two groups (67 and 60%).
CONCLUSIONS: The neurological manifestations of CD and NCGS are similar and equally responsive to a GFD
suggestive of common pathophysiological mechanisms
On the geometric distance between quantum states with positive partial transposition and private states
We prove an analytic positive lower bound for the geometric distance between
entangled positive partial transpose (PPT) states of a broad class and any
private state that delivers one secure key bit. Our proof holds for any Hilbert
space of finite dimension. Although our result is proven for a specific class
of PPT states, we show that our bound nonetheless holds for all known entangled
PPT states with non-zero distillable key rates whether or not they are in our
special class.Comment: 16 page
A preview of JWST metallicity studies at cosmic noon: the first detection of auroral [O II] emission at high redshift
Galaxie
The relativistic precession of the orbits
The relativistic precession can be quickly inferred from the nonlinear polar
orbit equation without actually solving it.Comment: Accepted for publication in Astrophysics & Space Scienc
Oral shedding of herpesviruses in HIV-infected patients with varying degrees of immune status
Objective: Herpesvirus shedding in the oral cavity was analyzed to determine if presence in the oral compartment correlates with systemic changes in HIV-associated immune deficiency as measured by CD4 + cell counts, plasma HIV viral load and presence of AIDS-defining events. Design: A5254 is a multicenter, cross-sectional, single-visit study to evaluate oral complications of HIV/AIDS and determine the association between clinical appearance, herpesvirus shedding, and immune status as ascertained by CD4 + cell count and HIV viral load. In total, 307 HIV-infected individuals were evaluated and throat wash collected. Methods: Fisher's exact test and Kruskal-Wallis test were used to assess the association between presence of herpesviruses and the state of immunodeficiency as stratified by a combination of CD4 + cell count and HIV viral load. Relationship between pathogens and HIV viral load in plasma was modeled by logistic regression. Results: The presence of cytomegalovirus (CMV) and herpes simplex virus-1 in throat wash was associated with decreased CD4 + cell counts. By contrast, Kaposi sarcoma-associated herpesvirus and Epstein-Barr virus were similarly detectable across all levels of CD4 + cell counts. One unit increase in log 10 (HIV viral load) was associated with 1.31 times higher odds of detecting CMV in throat wash when controlling for oral candidiasis, CD4 + cell count, and sites (95% confidence interval 1.04-1.65, P=0.02). Conclusion: Oral CMV shedding was significantly higher in highly immunocompromised HIV + participants. Our finding supports the recommendations to start antiretroviral therapy independent of CD4 + cell count as this may have the added benefit to lower the risk of herpesvirus transmission among persons infected with HIV and their partners
Quantitative Treatment of Decoherence
We outline different approaches to define and quantify decoherence. We argue
that a measure based on a properly defined norm of deviation of the density
matrix is appropriate for quantifying decoherence in quantum registers. For a
semiconductor double quantum dot qubit, evaluation of this measure is reviewed.
For a general class of decoherence processes, including those occurring in
semiconductor qubits, we argue that this measure is additive: It scales
linearly with the number of qubits.Comment: Revised version, 26 pages, in LaTeX, 3 EPS figure
Experimental and Numerical Investigation of Aerodynamic Performance of Airfoils Fitted with Morphing Trailing-edges
Metatranscriptomics analysis reveals a novel transcriptional and translational landscape during Middle East respiratory syndrome coronavirus infection
Among all RNA viruses, coronavirus RNA transcription is the most complex and involves a process termed “discontinuous transcription” that results in the production of a set of 3′-nested, co-terminal genomic and subgenomic RNAs during infection. While the expression of the classic canonical set of subgenomic RNAs depends on the recognition of a 6- to 7-nt transcription regulatory core sequence (TRS), here, we use deep sequence and metagenomics analysis strategies and show that the coronavirus transcriptome is even more vast and more complex than previously appreciated and involves the production of leader-containing transcripts that have canonical and noncanonical leader-body junctions. Moreover, by ribosome protection and proteomics analyses, we show that both positive- and negative-sense transcripts are translationally active. The data support the hypothesis that the coronavirus proteome is much vaster than previously noted in the literature
Measurement of the B0-anti-B0-Oscillation Frequency with Inclusive Dilepton Events
The - oscillation frequency has been measured with a sample of
23 million \B\bar B pairs collected with the BABAR detector at the PEP-II
asymmetric B Factory at SLAC. In this sample, we select events in which both B
mesons decay semileptonically and use the charge of the leptons to identify the
flavor of each B meson. A simultaneous fit to the decay time difference
distributions for opposite- and same-sign dilepton events gives ps.Comment: 7 pages, 1 figure, submitted to Physical Review Letter
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