Optically programmable electron spin memory using semiconductor quantum dots

The spin of a single electron subject to a static magnetic field provides a natural two-level system that is suitable for use as a quantum bit, the fundamental logical unit in a quantum computer. Semiconductor quantum dots fabricated by strain driven self-assembly are particularly attractive for the realization of spin quantum bits, as they can be controllably positioned, electronically coupled and embedded into active devices. It has been predicted that the atomic-like electronic structure of such quantum dots suppresses coupling of the spin to the solid-state quantum dot environment, thus protecting the 'spin' quantum information against decoherence. Here we demonstrate a single electron spin memory device in which the electron spin can be programmed by frequency selective optical excitation. We use the device to prepare single electron spins in semiconductor quantum dots with a well defined orientation, and directly measure the intrinsic spin flip time and its dependence on magnetic field. A very long spin lifetime is obtained, with a lower limit of about 20 milliseconds at a magnetic field of 4 tesla and at 1 kelvin.     

Strychnine-resistant inhibition in the retina

Zusammenfassung Konvulsive Dosen von Strychnin (0,25–0,8 mg/kg) erhöhten die Inipulsaktivität von Einzelfasern im N. opticus der Katze; die Hemmungsphasen in den on- und off-Antworten blieben jedoch bei 68 von 69 untersuchten Fasereinheiten erhalten. Die Ergebnisse beweisen die Existenz einer strychninresistenten Hemmung in der Retina.     

Elektroretinogramm und retinale Impulsaktivität in Hypothermie

Summary The effect of deep hypothermia on the single fibre activity of the optic nerve and on the electroretinogram has been studied in the cat. The ganglion cell activity of the retina has been found to be more resistant than the ERG against the effect of cooling. There is a marked delay in the restitution of theb-wave during rewarming.     

Participation of retinal mechanisms in DMT hallucinations

Zusammenfassung Intravenöse Injektionen von DMT (1–5 mg/kg) bewirkten neben einer Verkleinerung der visuell evozierten corticalen Potentiale und der lichtinduzierten phasischen Reaktionen retinaler Neurone auch eine starke Verminderung der Spontanaktivität in Einzelfasern des N. opticus. Die Befunde sprechen für eine Beteiligung retinaler Mechanismen beim Zustandekommen optischer Halluzinationen und lassen 5-HT als retinalen Transmitter vermuten.

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Supported by the Östereichischen Fonds zur Förderung der wissenschaftlichen Forschung.