2,663 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
DNA methylation age is accelerated in alcohol dependence.
Alcohol dependence (ALC) is a chronic, relapsing disorder that increases the burden of chronic disease and significantly contributes to numerous premature deaths each year. Previous research suggests that chronic, heavy alcohol consumption is associated with differential DNA methylation patterns. In addition, DNA methylation levels at certain CpG sites have been correlated with age. We used an epigenetic clock to investigate the potential role of excessive alcohol consumption in epigenetic aging. We explored this question in five independent cohorts, including DNA methylation data derived from datasets from blood (n = 129, n = 329), liver (n = 92, n = 49), and postmortem prefrontal cortex (n = 46). One blood dataset and one liver tissue dataset of individuals with ALC exhibited positive age acceleration (p < 0.0001 and p = 0.0069, respectively), whereas the other blood and liver tissue datasets both exhibited trends of positive age acceleration that were not significant (p = 0.83 and p = 0.57, respectively). Prefrontal cortex tissue exhibited a trend of negative age acceleration (p = 0.19). These results suggest that excessive alcohol consumption may be associated with epigenetic aging in a tissue-specific manner and warrants further investigation using multiple tissue samples from the same individuals
Damping of Nodal Fermions Caused by a Dissipative Mode
Using a superconductor in 2+1 dimensions we show that the
Nambu Goldstone fluctuations are replaced by dissipative excitations. We find
that the nodal quasi-particles damping is caused by the strong dissipative
excitations near the nodal points. As a result we find that the scattering
rates are linear in frequency and not cubic as predicted in the literature for
the ``d'' wave superconductors. Our results explain the recent angle resolved
photoemission spectroscopy and optical conductivity in the BSCCO high
compounds.Comment: 10 page
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
Abelian and non-Abelian geometric phases in adiabatic open quantum systems
We introduce a self-consistent framework for the analysis of both Abelian and
non-Abelian geometric phases associated with open quantum systems, undergoing
cyclic adiabatic evolution. We derive a general expression for geometric
phases, based on an adiabatic approximation developed within an inherently
open-systems approach. This expression provides a natural generalization of the
analogous one for closed quantum systems, and we prove that it satisfies all
the properties one might expect of a good definition of a geometric phase,
including gauge invariance. A striking consequence is the emergence of a finite
time interval for the observation of geometric phases. The formalism is
illustrated via the canonical example of a spin-1/2 particle in a
time-dependent magnetic field. Remarkably, the geometric phase in this case is
immune to dephasing and spontaneous emission in the renormalized Hamiltonian
eigenstate basis. This result positively impacts holonomic quantum computing.Comment: v3: 10 pages, 2 figures. Substantially expanded version. Includes a
proof of gauge invariance of the non-Abelian geometric phase, and an appendix
on the left and right eigenvectors of the superoperator in the Jordan for
The determinants of vulnerability to currency crises: country-specific factors versus regional factors
We investigate the determinants of exchange market pressures (EMP) for some new EU member states at both the national and regional levels, where macroeconomic and financial variables are considered as potential sources. The regional common factors are extracted from these variables by using dynamic factor analysis. The linear empirical analysis, in general, highlights the importance of country-specific factors to defend themselves against vulnerability in their external sectors. Yet, given a significant impact of the common component in credit on EMP, a contagion effect is apparent through the conduit of credit market integration across these countries under investigation
BioTile, A Perl based tool for the identification of differentially enriched regions in tiling microarray data
BACKGROUND: Genome-wide tiling array experiments are increasingly used for the analysis of DNA methylation. Because DNA methylation patterns are tissue and cell type specific, the detection of differentially methylated regions (DMRs) with small effect size is a necessary feature of tiling microarray ‘peak’ finding algorithms, as cellular heterogeneity within a studied tissue may lead to a dilution of the phenotypically relevant effects. Additionally, the ability to detect short length DMRs is necessary as biologically relevant signal may occur in focused regions throughout the genome. RESULTS: We present a free open-source Perl application, Binding Intensity Only Tile array analysis or “BioTile”, for the identification of differentially enriched regions (DERs) in tiling array data. The application of BioTile to non-smoothed data allows for the identification of shorter length and smaller effect-size DERs, while correcting for probe specific variation by inversely weighting on probe variance through a permutation corrected meta-analysis procedure employed at identified regions. BioTile exhibits higher power to identify significant DERs of low effect size and across shorter genomic stretches as compared to other peak finding algorithms, while not sacrificing power to detect longer DERs. CONCLUSION: BioTile represents an easy to use analysis option applicable to multiple microarray platforms, allowing for its integration into the analysis workflow of array data analysis
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