Proposal for Quantum Simulation via All-Optically Generated Tensor Network States

We devise an all-optical scheme for the generation of entangled multimode photonic states encoded in temporal modes of light. The scheme employs a nonlinear down-conversion process in an optical loop to generate one- and higher-dimensional tensor network states of light. We illustrate the principle with the generation of two different classes of entangled tensor network states and report on a variational algorithm to simulate the ground-state physics of many-body systems. We demonstrate that state-of-the-art optical devices are capable of determining the ground-state properties of the spin-1/2 Heisenberg model. Finally, implementations of the scheme are demonstrated to be robust against realistic losses and mode mismatch.Comment: 6 pages main text plus 6 pages Supplementary Material and many figures. Updated to published version. Comments welcom

García, Xavier (ed.) (2015). Joan Oliver-Joaquim Molas: Diàleg epistolar il·lustrat (1959-1982). Lleida: Pagès Editors, pp. 186

<p><i>Objectives</i>: Attention-deficit/hyperactivity disorder (ADHD) has been associated with spatial working memory as well as frontostriatal core deficits. However, it is still unclear how the link between these frontostriatal deficits and working memory function in ADHD differs in children and adults. This study examined spatial working memory in adults and children with ADHD, focussing on identifying regions demonstrating age-invariant or age-dependent abnormalities. <i>Methods</i>: We used functional magnetic resonance imaging to examine a group of 26 children and 35 adults to study load manipulated spatial working memory in patients and controls. <i>Results</i>: In comparison to healthy controls, patients demonstrated reduced positive parietal and frontostriatal load effects, i.e., less increase in brain activity from low to high load, despite similar task performance. In addition, younger patients showed negative load effects, i.e., a decrease in brain activity from low to high load, in medial prefrontal regions. Load effect differences between ADHD and controls that differed between age groups were found predominantly in prefrontal regions. Age-invariant load effect differences occurred predominantly in frontostriatal regions. <i>Conclusions</i>: The age-dependent deviations support the role of prefrontal maturation and compensation in ADHD, while the age-invariant alterations observed in frontostriatal regions provide further evidence that these regions reflect a core pathophysiology in ADHD.</p

Topographical distribution of EEG working memory effects.

<p>For adults and children, load dependent and load independent theta EEG effects are shown in subfigures <b>A</b> and <b>B</b>, respectively. Group differences are shown in <b>C</b> and <b>D</b>. The short arrow indicates p<0.05 (t >1.69) and the long arrow indicates p<0.01 (t >2.44).</p

Mean theta EEG GSP and GFS along with GSP/GFS-response accuracy interactions.

<p>Results for GSP (maintenance and baseline interval) are shown in the left panels of <b>A</b>, <b>B</b>, and <b>C</b>, whereas results for the GFS are shown in the right panels of <b>A</b>, <b>B</b>, and <b>C</b>. (** indicates p<0.001, * indicates p<0.05. n.s.: non-significant.</p

Theta GSP-BOLD and GFS-BOLD signal correlations.

<p>Within-group results for theta GSP-BOLD signal correlations are shown in <b>A</b>-<b>C</b>, while GFS-BOLD signal correlations are shown in <b>D</b>-<b>F</b>. Between-group comparisons are presented in <b>C</b> and <b>F</b>. For all subfigures, results are shown at p<0.001 (uncorrected), except for subfigure E (p<0.01, uncorrected). Abbreviations: PPC, posterior parietal lobe; MFG, middle frontal gyrus; MPFC, medial prefrontal cortex; PCC, posterior cingulate cortex, R, right hemisphere; L, left hemisphere.</p

Load dependent fMRI activation differences between adults and children.

<p>Results are reported at a voxel threshold of p<0.001 (uncorrected) with a cluster-correction of p<0.05. R, right; L, left; IPL, inferior parietal lobe; STG, superior temporal gyrus; MFG, middle frontal gyrus; SFG, superior frontal gyrus; FG, fusiform gyrus; MPFC, medial prefrontal cortex.</p

Supplemental Material, JBD727871_supplementary_table - Increasing expertise to a novel script modulates the visual N1 ERP in healthy adults

<p> Supplemental Material, JBD727871_supplementary_table for Increasing expertise to a novel script modulates the visual N1 ERP in healthy adults by Urs Maurer, Catherine McBride, Silvia Brem, Eliane Hunkeler, Markus Mächler, Jens Kronschnabel, Iliana Irini Karipidis, Georgette Pleisch, and Daniel Brandeis in International Journal of Behavioral Development </p

Supplemental Material, JBD727871_supplementary_figures - Increasing expertise to a novel script modulates the visual N1 ERP in healthy adults

<p> Supplemental Material, JBD727871_supplementary_figures for Increasing expertise to a novel script modulates the visual N1 ERP in healthy adults by Urs Maurer, Catherine McBride, Silvia Brem, Eliane Hunkeler, Markus Mächler, Jens Kronschnabel, Iliana Irini Karipidis, Georgette Pleisch, and Daniel Brandeis in International Journal of Behavioral Development </p

Schematic timeline of the experimental design.

<p>ASL: arterial spin labelling, WM: working memory.</p

Representative MEGA-PRESS spectra.

<p>(A) Averaged MEGA-PRESS spectra (averaged across the subject group) acquired at rest (left) and during the WM task. The GABA peak at 3.0 ppm appears to increase between the resting spectrum and the first WM spectrum, and then decrease during performance of the WM task (panels 2-5). The dashed line marks the resting state peak. Glx: glutamate + glutamine concentration, GABA: gamma-aminobutyric acid, NAA: N-acetylaspartate, IU: institutional units. (B) LCModel output for a single subject: the fit is shown in red, superimposed on the edited spectrum (in black). The top panel shows the residuals between the MRS data and the spectral fit.</p