Universal Dephasing Control During Quantum Computation

Dephasing is a ubiquitous phenomenon that leads to the loss of coherence in quantum systems and the corruption of quantum information. We present a universal dynamical control approach to combat dephasing during all stages of quantum computation, namely, storage, single- and two-qubit operators. We show that (a) tailoring multi-frequency gate pulses to the dephasing dynamics can increase fidelity; (b) cross-dephasing, introduced by entanglement, can be eliminated by appropriate control fields; (c) counter-intuitively and contrary to previous schemes, one can increase the gate duration, while simultaneously increasing the total gate fidelity.Comment: 4 pages,3 figure

Borderline Personality Features and Integration of Positive and Negative Thoughts About Significant Others

Taking the bad with the good is a necessity of life, and people who readily integrate thoughts of their loved one’s flaws with thoughts of their more positive attributes maintain more stable, satisfying relationships. Borderline personality disorder, however, is often characterized by interpersonal perceptions that fluctuate between extremes of good and bad. We used a timed judgment task to examine information processing about significant others in individuals high in borderline personality features relative to healthy individuals and those high in avoidant personality features. In Study 1, when judging traits of a liked significant other, same-valence facilitation by negative primes (judging negative traits faster than positive traits after a negative prime) was significantly stronger in the borderline features group than the other two groups, and was inversely associated with self-reports of integrated thoughts about significant others. In contrast, same-valence facilitation by positive primes (judging positive traits faster than negative traits after a positive prime) was significantly stronger in the avoidant features group than the other two groups, and inversely associated with self-esteem. No between-group differences in same-valence facilitation were statistically significant when participants judged traits of disliked significant others, liked foods, and disliked foods. In Study 2, same-valence facilitation by negative primes when judging traits of a liked significant other was significantly associated with less integrated positive/negative thoughts about that person in a 12-day diary. These results identify an implicit information-processing pattern relevant to interpersonal difficulties in borderline personality disorder

Organization and oscillations in simulated shallow convective clouds

Physical insights into processes governing temporal organization and evolution of cloud fields are of great importance for climate research. Here using large eddy simulations with a bin microphysics scheme, we show that warm convective cloud fields exhibit oscillations with two distinct periods (~10 and ~90 min, for the case studied here). The shorter period dominates the nonprecipitating phase, and the longer period is related to the precipitating phase. We show that rain processes affect the domain\u27s thermodynamics, hence forcing the field into a low‐frequency recharge‐discharge cycle of developing cloudiness followed by precipitation‐driven depletion. The end result of precipitation is stabilization of the lower atmosphere by warming of the cloudy layer (due to latent heat release) and cooling of the subcloud layer (by rain evaporation, creating cold pools). As the thermodynamic instability weakens, so does the cloudiness, and the rain ceases. During the nonprecipitating phase of the cycle, surface fluxes destabilize the boundary layer until the next precipitation cycle. Under conditions that do not allow development of precipitation (e.g., high aerosol loading), high‐frequency oscillations dominate the cloud field. Clouds penetrating the stable inversion layer trigger gravity waves with a typical period of ~10 min. In return, the gravity waves modulate the clouds in the field by modifying the vertical velocity, temperature, and humidity fields. Subsequently, as the polluted nonprecipitating simulations evolve, the thermodynamic instability increases and the cloudy layer deepens until precipitation forms, shifting the oscillations from high to low frequency. The organization of cold pools and the spatial scale related to these oscillations are explored

Universal dynamical decoherence control of noisy single-and multi-qubit systems

In this article we develop, step by step, the framework for universal dynamical control of two-level systems (TLS) or qubits experiencing amplitude- or phase-noise (AN or PN) due to coupling to a thermal bath. A comprehensive arsenal of modulation schemes is introduced and applied to either AN or PN, resulting in completely analogous formulae for the decoherence rates, thus underscoring the unified nature of this universal formalism. We then address the extension of this formalism to multipartite decoherence control, where symmetries are exploited to overcome decoherence.Comment: 28 pages, 4 figure

Impeded Growth of Magnetic Flux Bubbles in the Intermediate State Pattern of Type I Superconductors

Normal state bubble patterns in Type I superconducting Indium and Lead slabs are studied by the high resolution magneto-optical imaging technique. The size of bubbles is found to be almost independent of the long-range interaction between the normal state domains. Under bubble diameter and slab thickness proper scaling, the results gather onto a single master curve. On this basis, in the framework of the "current-loop" model [R.E. Goldstein, D.P. Jackson and A.T. Dorsey, Phys. Rev. Lett. 76, 3818 (1996)], we calculate the equilibrium diameter of an isolated bubble resulting from the competition between the Biot-and-Savart interaction of the Meissner current encircling the bubble and the superconductor-normal interface energy. A good quantitative agreement with the master curve is found over two decades of the magnetic Bond number. The isolation of each bubble in the superconducting matrix and the existence of a positive interface energy are shown to preclude any continuous size variation of the bubbles after their formation, contrary to the prediction of mean-field models.Comment: \'{e}quipe Nanostructures Quantique

Dissociations of Face and Object Recognition in Developmental Prosopagnosia

Neuropsychological studies with patients suffering from prosopagnosia have provided the main evidence for the hypothesis that the recognition of faces and objects rely on distinct mechanisms. Yet doubts remain, and it has been argued that no case demonstrating an unequivocal dissociation between face and object recognition exists due in part to the lack of appropriate response time measurements (Gauthier et al., 1999). We tested seven developmental prosopagnosics to measure their accuracy and reaction times with multiple tests of face recognition and compared this with a larger battery of object recognition tests. For our systematic comparison, we used an old/new recognition memory paradigm involving memory tests for cars, tools, guns, horses, natural scenes, and houses in addition to two separate tests for faces. Developmental prosopagnosic subjects performed very poorly with the face memory tests as expected. Four of the seven prosopagnosics showed a very strong dissociation between the face and object tests. Systematic comparison of reaction time measurements for all tests indicates that the dissociations cannot be accounted for by differences in reaction times. Contrary to an account based on speed accuracy tradeoffs, prosopagnosics were systematically faster in nonface tests than in face tests. Thus, our findings demonstrate that face and nonface recognition can dissociate over a wide range of testing conditions. This is further support for the hypothesis that face and nonface recognition relies on separate mechanisms and that developmental prosopagnosia constitutes a disorder separate from developmental agnosia

Taking Foreign Policy Personally: Personal Values and Foreign Policy Attitudes

Previous research has shown that on issues of foreign policy, individuals have “general stances,” “postures,” “dispositions” or “orientations” that inform their beliefs toward more discrete issues in international relations. While these approaches delineate the proximate sources of public opinion in the foreign policy domain, they evade an even more important question: what gives rise to these foreign policy orientations in the first place? Combining an original survey on a nationally representative sample of Americans with Schwartz’s theory of values from political psychology, we show that people take foreign policy personally: the same basic values we know people use to guide choices in their daily lives also travel to the domain of foreign affairs, offering one potential explanation why people who are otherwise uninformed about world politics nonetheless express coherent foreign policy beliefs

Dynamics and Selection of Giant Spirals in Rayleigh-Benard Convection

For Rayleigh-Benard convection of a fluid with Prandtl number \sigma \approx 1, we report experimental and theoretical results on a pattern selection mechanism for cell-filling, giant, rotating spirals. We show that the pattern selection in a certain limit can be explained quantitatively by a phase-diffusion mechanism. This mechanism for pattern selection is very different from that for spirals in excitable media