6,416 research outputs found
An analytical decomposition protocol for optimal implementation of two-qubit entangling gates
This paper addresses the question how to implement a desired two-qubit gate U
using a given tunable two-qubit entangling interaction H_int. We present a
general method which is based on the K_1 A K_2 decomposition of unitary
matrices in SU(4) to calculate analytically the smallest number of two-qubit
gates U_int [based on H_int] and single-qubit rotations, and the explicit
sequence of these operations that are required to implement U. We illustrate
our protocol by calculating the implementation of (1) the transformation from
standard basis to Bell basis, (2) the CNOT gate, and (3) the quantum Fourier
transform for two kinds of interaction - Heisenberg exchange interaction and
quantum inductive coupling - and discuss the relevance of our results for
solid-state qubits.Comment: 16 pages, published versio
Duurzaam verwerken van grof huishoudelijk afval : een onderzoek naar de knelpunten die duurzamer verwerking van grof afval verhinderen
High-pressure study of the non-Fermi liquid material U_2Pt_2In
The effect of hydrostatic pressure (p<= 1.8 GPa) on the non-Fermi liquid
state of U_2Pt_2In is investigated by electrical resistivity measurements in
the temperature interval 0.3-300 K. The experiments were carried out on
single-crystals with the current along (I||c) and perpendicular (I||a) to the
tetragonal axis. The pressure effect is strongly current-direction dependent.
For I||a we observe a rapid recovery of the Fermi-liquid T^2-term with
pressure. The low-temperature resistivity can be analysed satisfactorily within
the magnetotransport theory of Rosch, which provides strong evidence for the
location of U_2Pt_2In at an antiferromagnetic quantum critical point. For I||c
the resistivity increases under pressure, indicating the enhancement of an
additional scattering mechanism. In addition, we have measured the pressure
dependence of the antiferromagnetic ordering temperature (T_N= 37.6 K) of the
related compound U_2Pd_2In. A simple Doniach-type diagram for U_2Pt_2In and
U_2Pd_2In under pressure is presented.Comment: 21 pages (including 5 figures); pdf forma
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Factor Structure of the Edinburgh Postnatal Depression Scale in a Population-Based Sample
To demonstrate validity, questionnaires should measure the same construct in different groups and across time. The Edinburgh Postnatal Depression Scale (EPDS) was designed as a unidimensional scale, but factor analyses of the EPDS have been equivocal, and demonstrate other structures: this may be because of sample characteristics and timing of administration. We aimed to examine the factor structure of the EPDS in pregnancy and postpartum at 4 time-points in a large population-based sample. We carried out exploratory and confirmatory factor analysis on the Avon Longitudinal Study of Parents and Children sample (n = 11,195–12,166) randomly split in 2. We used data from 18 and 32 weeks pregnancy gestation; and 8 weeks and 8 months postpartum. A 3-factor solution was optimal at all time-points, showing the clearest factor structure and best model fit: Depression (4 items) accounted for 43.5–47.2% of the variance; anhedonia (2 items) 10.5–11.1%; and anxiety (3 items) 8.3–9.4% of the variance. Internal reliability of subscales was good at all time points (Cronbach’s αs: .73–.78). The EPDS appears to measure 3 related factors of depression, anhedonia, and anxiety and has a stable structure in pregnancy and the first postnatal year
Numerical and asymptotic solutions of generalised Burgers’ equation
The generalised Burgers’ equation has been subject to a considerable amount of research on how the equation should behave according to asymptotic analysis, however there has been limited research verifying the asymptotic analysis. In order to verify the asymptotic analysis, this paper aims to run long time and detailed numerical simulations of Burgers’ equation by employing suitable rescalings of Burgers’ equation. It is hoped that this technique will make it possible to notice subtle changes in the shock structure which would otherwise be impossible to observe. The main aim of this paper is to validate the numerical methods used in order to allow further research into shock evolution where further relaxation effects will be included
Ordered magnetic and quadrupolar states under hydrostatic pressure in orthorhombic PrCu2
We report magnetic susceptibility and electrical resistivity measurements on
single-crystalline PrCu2 under hydrostatic pressure, up to 2 GPa, which
pressure range covers the pressure-induced Van Vleck
paramagnet-to-antiferromagnet transition at 1.2 GPa. The measured anisotropy in
the susceptibility shows that in the pressure-induced magnetic state the
ordered 4f-moments lie in the ac-plane. We propose that remarkable pressure
effects on the susceptibility and resistivity are due to changes in the
quadrupolar state of O22 and/or O20 under pressure. We present a simple
analysis in terms of the singlet-singlet model.Comment: 14 pages, 9 figures submitted to Phys. Rev.
On optical black holes in moving dielectrics
We study the optical paths of the light rays propagating inside a nonlinear
moving dielectric media. For the rapidly moving dielectrics we show the
existence of a distinguished surface which resembles, as far as the light
propagation is concerned, the event horizon of a black hole. Our analysis
clarifies the physical conditions under which electromagnetic analogues of the
gravitational black holes can eventually be obtained in laboratory.Comment: 5 pages, 2 figures, revtex
Might EPR particles communicate through a wormhole?
We consider the two-particle wave function of an Einstein-Podolsky-Rosen
system, given by a two dimensional relativistic scalar field model. The Bohm-de
Broglie interpretation is applied and the quantum potential is viewed as
modifying the Minkowski geometry. In this way an effective metric, which is
analogous to a black hole metric in some limited region, is obtained in one
case and a particular metric with singularities appears in the other case,
opening the possibility, following Holland, of interpreting the EPR
correlations as being originated by an effective wormhole geometry, through
which the physical signals can propagate.Comment: Corrected version, to appears in EP
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