Real-time quantum feedback prepares and stabilizes photon number states

Feedback loops are central to most classical control procedures. A controller compares the signal measured by a sensor (system output) with the target value or set-point. It then adjusts an actuator (system input) to stabilize the signal around the target value. Generalizing this scheme to stabilize a micro-system's quantum state relies on quantum feedback, which must overcome a fundamental difficulty: the sensor measurements cause a random back-action on the system. An optimal compromise uses weak measurements, providing partial information with minimal perturbation. The controller should include the effect of this perturbation in the computation of the actuator's operation, which brings the incrementally perturbed state closer to the target. Although some aspects of this scenario have been experimentally demonstrated for the control of quantum or classical micro-system variables, continuous feedback loop operations that permanently stabilize quantum systems around a target state have not yet been realized. Here we have implemented such a real-time stabilizing quantum feedback scheme following a method inspired by ref. 13. It prepares on demand photon number states (Fock states) of a microwave field in a superconducting cavity, and subsequently reverses the effects of decoherence-induced field quantum jumps. The sensor is a beam of atoms crossing the cavity, which repeatedly performs weak quantum non-demolition measurements of the photon number. The controller is implemented in a real-time computer commanding the actuator, which injects adjusted small classical fields into the cavity between measurements. The microwave field is a quantum oscillator usable as a quantum memory or as a quantum bus swapping information between atoms. Our experiment demonstrates that active control can generate non-classical states of this oscillator and combat their decoherence, and is a significant step towards the implementation of complex quantum information operations.     

Intrusion triggering of the 2010 Eyjafjallajökull explosive eruption

Gradual inflation of magma chambers often precedes eruptions at highly active volcanoes. During such eruptions, rapid deflation occurs as magma flows out and pressure is reduced. Less is known about the deformation style at moderately active volcanoes, such as Eyjafjallaj?kull, Iceland, where an explosive summit eruption of trachyandesite beginning on 14 April 2010 caused exceptional disruption to air traffic, closing airspace over much of Europe for days. This eruption was preceded by an effusive flank eruption of basalt from 20 March to 12 April 2010. The 2010 eruptions are the culmination of 18?years of intermittent volcanic unrest. Here we show that deformation associated with the eruptions was unusual because it did not relate to pressure changes within a single magma chamber. Deformation was rapid before the first eruption (>5?mm per day after 4 March), but negligible during it. Lack of distinct co-eruptive deflation indicates that the net volume of magma drained from shallow depth during this eruption was small; rather, magma flowed from considerable depth. Before the eruption, a ～0.05?km(3) magmatic intrusion grew over a period of three months, in a temporally and spatially complex manner, as revealed by GPS (Global Positioning System) geodetic measurements and interferometric analysis of satellite radar images. The second eruption occurred within the ice-capped caldera of the volcano, with explosivity amplified by magma-ice interaction. Gradual contraction of a source, distinct from the pre-eruptive inflation sources, is evident from geodetic data. Eyjafjallaj?kull's behaviour can be attributed to its off-rift setting with a 'cold' subsurface structure and limited magma at shallow depth, as may be typical for moderately active volcanoes. Clear signs of volcanic unrest signals over years to weeks may indicate reawakening of such volcanoes, whereas immediate short-term eruption precursors may be subtle and difficult to detect.     

Effect of coenzyme-A, NAD, alpha lipoic-acid and cocarboxylase on survival of rats with galactosamine-induced severe hepatitis

Galactosamine, a selective hepatotoxin, produces in rats histologic alterations, which show the characteristics of severe human viral hepatitis. In the present study the efficacy of two different cofactor regimens (coenzyme A, NAD, alpha lipoic-acid, cocarboxylase) in rats with fulminant galactosamine hepatitis were tested. The results showed an improvement of the short-term survival with a short-term treatment and definitely better survival with a long-term regimen with cofactors.     

Zur Pathogenese des Urämiesyndroms1. Über den Einfluss von Tyramin auf die Acetoinsynthese aus Brenztraubensäure in Rattenleberhomogenat2

Summary Tyramine enhanced the production of acetoin from pyruvate in rat liver homogenates. A stimulation of acetoin synthesis was only observed, when tyramine was oxidized during the incubation. Tyrosol (p-hydroxyphenylethanol) stimulated acetoin synthesis whereasp-hydroxyphenylacetic acid and ammonia were ineffective.

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Mit Unterstützung des »Schweizerischen Nationalfonds» und der Firma F. Hoffmann-La Roche & Co. AG, Basel.

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8. Mitteilung. 1. Mitt.:H. Thölen, F. Bigler undH. Staub, Path. Microbiol. (Basel)24, 262 (1961). — 2. Mitt.:F. Bigler, H. Thölen undH. Staub, Helv. physiol. Acta19, C 11 (1961). — 3. Mitt.:H. Thölen, F. Bigler undH. Staub, Exper.17, 359 (1961). — 4. Mitt.:F. Bigler, H. Thölen undH. Staub, Schweiz. med. Wschr.91, 1259 (1961). — 5. Mitt.:H. Thölen, F. Bigler, A. Heusler, W. Stauffacher undH. Staub, Exper.18, 454 (1962). — 6. Mitt.:F. Bigler, H. Thölen undH. Staub, Schweiz. med. Wschr.92, 746 (1962). — 7. Mitt.:F. Bigler, H. Thölen undH. Staub, in Vorbereitung.     

Pathogenesis of the uremic syndrome. Pharmacological studies on acetoin and 2,3-butylene glycol

Zusammenfassung Acetoin und 2,3-Butylenglykol entstehen bei Menschen und Tieren aus Brenztraubensäure. Beide Substanzen bewirken bei Mäusen Narkose. Bei Ratten tritt der Bezold-Jarisch-Reflex auf. Die Rolle von Acetoin und 2,3-Butylenglykol bei urämischen und hepatischen Bewusstseinsstörungen wird diskutiert.

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The study was aided by grants from Schweizerischer Nationalfonds' and from F. Hoffmann-La Roche & Co. AG, Basel.

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3rd Communication. 2nd Commun. see:F. Bigler, H. Thölen, andH. Staub, Helv. physiol. pharmacol. Acta19, C 11 (1961).     

Perception of the geomagnetic field in the flyDrosophila melanogaster

Zusammenfassung Die negativ geotaktische Orientierung vonDrosophila melanogaster auf einer 30° geneigten Ebene zeigt eine signifikante Abweichung nach links (5.5°), wenn die Linien des Erdmagnetfeldes lateral zur Fortbewegungsrichtung der Fliegen einfallen. Auf einer horizontalen Ebene bevorzugen die Fliegen als Ruhestellungen die N/S- und W/E-Richtungen.     

Konstitutionsaufklärung und Synthese von Psilocybin

Summary The structure of Psilocybin, the psychotropic active principle of the Mexican mushroomPsilocybe mexicana Heim, has been elucidated. Psilocybin is the phosphoric acid ester of 4-hydroxy-dimethyltryptamine. This structure was confirmed by total synthesis.