University of Konstanz

About: University of Konstanz is a education organization based out in Konstanz, Baden-Württemberg, Germany. It is known for research contribution in the topics: Population & Visualization. The organization has 12115 authors who have published 27401 publications receiving 951162 citations. The organization is also known as: University of Constance & Universität Konstanz.

Femtosecond laser near-field ablation from gold nanoparticles

Abstract: Short-pulse laser ablation is promising owing to the low threshold for material removal from surfaces. In the laser-ablation process, solid material transforms into a volatile phase initiated by a rapid deposition of energy. Explosive boiling can be one of the mechanisms in which matter is heated close to the critical point. Other pathways of non-thermal excitation will be present for very short laser pulses1. Here we observe a different channel of ablation from gold nanoparticles, which takes place below the particle melting point. This process is induced by the optical near-field, a subwavelength field enhancement close to curved surfaces, in particular. Using picosecond X-ray scattering, we can track the temporal and energetic structural dynamics during material ejection from the nanoparticles. This effect will limit any high-power laser manipulation of nanostructured surfaces, such as surface-enhanced Raman measurements2 or plasmonics with femtosecond pulses.

Representational cortex in musicians. Plastic alterations in response to musical practice.

Abstract: The lifelong ability to adapt to environmental needs is based on the capacity of the central nervous system for plastic alterations. In a series of neurophysiological experiments, we studied the impact of music and musical training in musicians on the specific functional organization in auditory and somatosensory representational cortex. In one such study, subjects listened to music from which one specific spectral frequency was removed. This led to rapid and reversible adaptation of neuronal responses in auditory cortex. Further experimental evidence demonstrated that long years of practice and training by professional musicians to enable them to reach their capacity is associated with enlarged cortical representations in the somatosensory and auditory domains. This tuning of neuronal representations was specifically observed for musical tones and was absent when pure sinusoidal tones were used as stimuli. In the somatosensory cortex, plastic changes proved to be specific for the fingers frequently used and stimulated. These changes were not detected in the fingers of the hand that were not involved in playing the particular instrument. Neuroplastic alterations also may be driven into a domain where they may become maladaptive. The clinical syndrome of focal hand dystonia that may occur in musicians who engage in forceful practice may be one such consequence. We will discuss the possibilities of reversing maladaptive responses leading to the successful treatment of focal hand dystonia, which relies on basic research about cortical reorganization. This example elucidates how neuroscientific progress can guide the development of practice guidelines and therapeutic measures for the benefit of professional musicians.

Accelerated quantum control using superadiabatic dynamics in a solid-state lambda system

Abstract: Adiabatic processes are useful in quantum control, but they are slow. A way around this is to exploit shortcuts to adiabaticity, which can speed things up — for instance, by boosting stimulated Raman adiabatic passage. Adiabatic processes are useful for quantum technologies1,2,3 but, despite their robustness to experimental imperfections, they remain susceptible to decoherence due to their long evolution time. A general strategy termed shortcuts to adiabaticity4,5,6,7,8,9 (STA) aims to remedy this vulnerability by designing fast dynamics to reproduce the results of a slow, adiabatic evolution. Here, we implement an STA technique known as superadiabatic transitionless driving10 (SATD) to speed up stimulated Raman adiabatic passage1,11,12,13,14 in a solid-state lambda system. Using the optical transitions to a dissipative excited state in the nitrogen-vacancy centre in diamond, we demonstrate the accelerated performance of different shortcut trajectories for population transfer and for the initialization and transfer of coherent superpositions. We reveal that SATD protocols exhibit robustness to dissipation and experimental uncertainty, and can be optimized when these effects are present. These results suggest that STA could be effective for controlling a variety of solid-state open quantum systems11,12,13,14,15,16.