A surface-electrode quadrupole guide for electrons

This thesis reports on the design and first experimental realization of a surface-electrode quadrupole guide for free electrons. The guide is based on a miniaturized, planar electrode layout and is driven at microwave frequencies. It confines electrons in the near-field of the microwave excitation, where strong electric field gradients can be generated without resorting to resonating structures or exceptionally high drive powers. The use of chip-based electrode geometries allows the realization of versatile, microstructured potentials with the perspective of novel quantum experiments with guided electrons. I present the design, construction and operation of an experiment that demonstrates electron confinement in a planar quadrupole guide for the first time. To this end, electrons with kinetic energies from one to ten electron-volts are guided along a curved electrode geometry. The stability of electron guiding as a function of drive parameters and electron energy has been studied. A comparison with numerical particle tracking simulations yields good qualitative agreement and provides a deeper understanding of the electron dynamics in the guiding potential. Furthermore, this thesis gives a detailed description of the design of the surface-electrode layout. This includes the development of an optimized coupling structure to inject electrons into the guide with minimum transverse excitation. I also discuss the extension of the current setup to longitudinal guide dimensions that are comparable to or larger than the wavelength of the drive signal. This is possible with a modified electrode layout featuring elevated signal conductors. Electron guiding in the field of a planar, microfabricated electrode layout allows the generation of versatile and finely structured guiding potentials. One example would be the realization of junctions that split and recombine a guided electron beam. Furthermore, it should be possible to prepare electrons in low-lying quantum mechanical oscillator states of the transverse guiding potential by matching an incoming electron beam to the wave functions of these states.Thema dieser Arbeit ist der Entwurf und die experimentelle Realisierung eines Quadrupolleiters für freie Elektronen. Dieser basiert auf einer miniaturisierten, planaren Elektrodenkonfiguration und wird mit einem Mikrowellensignal betrieben. Der Elektroneneinschluß findet im Nahfeld der Mikrowellenanregung statt. Dort lassen sich hohe elektrische Feldgradienten mit moderaten Spannungen erzeugen, ohne Resonatoren zur Spannungsüberhöhung verwenden zu müssen. Der Einsatz von mikrofabrizierten Elektrodengeometrien erlaubt es, vielfältige Potentiallandschaften zu erzeugen, die auf kleinen Skalen strukturiert werden können. Dies eröffnet die Perspektive, neuartige Quantenexperimente mit freien Elektronen zu realisieren. Im Rahmen dieser Arbeit wurde ein Experiment entworfen, aufgebaut und ausgeführt, das zum ersten Mal den Einschluß freier Elektronen in einem miniaturisierten Quadrupolleiter demonstriert. Langsame Elektronen mit Energien von einem bis zu zehn Elektronenvolt werden hierzu entlang einer gebogenen Elektrodenstruktur geführt. Um das Fallenpotential zu charakterisieren, wurde die Stabilität der Elektronenbewegung in Abhängigkeit der Treiberparameter und der Elektronenenergie untersucht. Die Ergebnisse stimmen qualitativ gut mit numerischen Simulationen der Teilchentrajektorien überein, was zu einem tieferen Verständnis der Elektronendynamik im Leiterpotential führt. In der vorliegenden Arbeit wird außerdem der Entwurf der verwendeten Elektrodengeometrie detailliert beschrieben. Dies beinhaltet die Entwicklung einer optimierten Einkoppelstruktur, welche es erlaubt, Elektronen unter geringer transversaler Anregung in das Quadrupolpotential einzuspeisen. Ich beschreibe auch eine mögliche Erweiterung des momentanen Aufbaus um Strukturen, deren Länge vergleichbar mit oder größer als die Wellenlänge des Treibersignals ist. Dies läßt sich mit einer modifizierten Elektrodengeometrie erreichen, die aus erhöhten Signalleitern über einer geerdeten Fläche besteht. Ein Beispiel für die vielfältigen Potentiale für Elektronen, die mit mikrostrukturierten Elektrodengeometrien erzeugt werden könnten, sind Strahlteiler zum Aufspalten und anschließenden Zusammenführen eines eingeschlossenen Elektronenstrahls. Außerdem sollte es möglich sein, Elektronen in niedrigliegenden quantenmechanischen Zuständen des transversalen Potentials zu präparieren, indem der einfallende Elektronenstrahl an die Wellenfunktionen der geführten Elektronen angepaßt wird

Coherent manipulation of Bose-Einstein condensates with state-dependent microwave potentials on an atom chip

Entanglement-based technologies, such as quantum information processing, quantum simulations, and quantum-enhanced metrology, have the potential to revolutionise our way of computing and measuring and help clarifying the puzzling concept of entanglement itself. Ultracold atoms on atom chips are attractive for their implementation, as they provide control over quantum systems in compact, robust, and scalable setups. An important tool in this system is a potential depending on the internal atomic state. Coherent dynamics in this potential combined with collisional interactions allows entanglement generation both for individual atoms and ensembles. Here, we demonstrate coherent manipulation of Bose-condensed atoms in such a potential, generated in a novel way with microwave near-fields on an atom chip. We reversibly entangle atomic internal and motional states, realizing a trapped-atom interferometer with internal-state labelling. Our system provides control over collisions in mesoscopic condensates, paving the way for on-chip generation of many-particle entanglement and quantum-enhanced metrology with spin-squeezed states.Comment: 9 pages, 6 figure

Acupuncture in acute herpes zoster pain therapy (ACUZoster) - design and protocol of a randomised controlled trial

Background: Acute herpes zoster is a prevalent condition. One of its major symptoms is pain, which can highly influence patient's quality of life. Pain therapy is limited. Acupuncture is supposed to soften neuropathic pain conditions and might therefore act as a therapeutic alternative. Objective of the present study is to investigate whether a 4 week semi-standardised acupuncture is non-inferior to sham laser acupuncture and the anticonvulsive drug gabapentine in the treatment of pain associated with herpes zoster. Methods/Design: Three-armed, randomised, placebo-controlled trial with a total follow-up time of 6 months. Up to estimated 336 patients (interim analyses) with acute herpes zoster pain (VAS > 30 mm) will be randomised to one of three groups (a) semi-standardised acupuncture (168 patients); (b) gabapentine with individualised dosage between 900-3600 mg/d (84 patients); (c) sham laser acupuncture. Intervention takes place over 4 weeks, all patients will receive analgesic therapy (non-opioid analgesics: metamizol or paracetamol and opioids: tramadol or morphine). Therapy phase includes 4 weeks in which group (a) and (c) consist of 12 sessions per patient, (b) visits depend on patients needs. Main outcome measure is to assess the alteration of pain intensity before and 1 week after treatment sessions (visual analogue scale VAS 0-100 mm). Secondary outcome measure are: alteration of pain intensity and frequency of pain attacks; alteration of different aspects of pain evaluated by standardised pain questionnaires (NPI, PDI, SES); effects on quality of life (SF 36); analgesic demand; alteration of sensoric perception by systematic quantitative sensory testing (QST); incidence of postherpetic neuralgia; side effects and cost effectiveness. Credibility of treatments will be assessed. Discussion: This study is the first large-scale randomised placebo controlled trial to evaluate the efficacy of acupuncture compared to gabapentine and sham treatment and will provide valuable new information about the clinical and physiological effects of acupuncture and gabapentine in the treatment of acute herpes zoster pain. The study has been pragmatically designed to ensure that the study findings can be implemented into clinical practice if acupuncture can be shown to be an effective treatment strategy in acute herpes zoster pain

Acupuncture in acute herpes zoster pain therapy (ACUZoster) – design and protocol of a randomised controlled trial

Abstract Background Acute herpes zoster is a prevalent condition. One of its major symptoms is pain, which can highly influence patient's quality of life. Pain therapy is limited. Acupuncture is supposed to soften neuropathic pain conditions and might therefore act as a therapeutic alternative. Objective of the present study is to investigate whether a 4 week semi-standardised acupuncture is non-inferior to sham laser acupuncture and the anticonvulsive drug gabapentine in the treatment of pain associated with herpes zoster. Methods/Design Three-armed, randomised, placebo-controlled trial with a total follow-up time of 6 months. Up to estimated 336 patients (interim analyses) with acute herpes zoster pain (VAS > 30 mm) will be randomised to one of three groups (a) semi-standardised acupuncture (168 patients); (b) gabapentine with individualised dosage between 900–3600 mg/d (84 patients); (c) sham laser acupuncture. Intervention takes place over 4 weeks, all patients will receive analgesic therapy (non-opioid analgesics: metamizol or paracetamol and opioids: tramadol or morphine). Therapy phase includes 4 weeks in which group (a) and (c) consist of 12 sessions per patient, (b) visits depend on patients needs. Main outcome measure is to assess the alteration of pain intensity before and 1 week after treatment sessions (visual analogue scale VAS 0–100 mm). Secondary outcome measure are: alteration of pain intensity and frequency of pain attacks; alteration of different aspects of pain evaluated by standardised pain questionnaires (NPI, PDI, SES); effects on quality of life (SF 36); analgesic demand; alteration of sensoric perception by systematic quantitative sensory testing (QST); incidence of postherpetic neuralgia; side effects and cost effectiveness. Credibility of treatments will be assessed. Discussion This study is the first large-scale randomised placebo controlled trial to evaluate the efficacy of acupuncture compared to gabapentine and sham treatment and will provide valuable new information about the clinical and physiological effects of acupuncture and gabapentine in the treatment of acute herpes zoster pain. The study has been pragmatically designed to ensure that the study findings can be implemented into clinical practice if acupuncture can be shown to be an effective treatment strategy in acute herpes zoster pain. Trial registration NCT00885586</p