Development of novel coherent electron field emission sources:
Electron beam emitters are applied in various fields of science and technology such as in electron microscopy, surface spectroscopy, matter-wave interferometry or sensor technology. Usually they are realized by an etched metal tip set on a high voltage in vacuum. Our aim is to realize novel electron beam sources that apply the quantum nature of the emitter or the emitted electrons. This can significantly increase the beam intensity and reduce the energy spread of the emitted electrons that in turn decreases the beam aberrations from electron optical components such es e.g. lenses in electron microscopes. Another goal is to realize beam sources that emit electrons in a highly coherent quantum state or even as entangled, correlated pairs such as theoretically predicted from superconducting niobium nanotips. These kind of sources would have significant applications in electron spectroscopy and quantum information science.
Information transfer by a quantum modulation of electron matter-waves:
Classical signal transmission relies on the modulation of electromagnetic waves. In the recent decades fascinating novel and secure quantum information transfer techniques were discovered and are already commercially available. They use the quantum features of photons. Our approach is to apply the matter-wave nature of electrons for a fundamentally new method of quantum signal transmission. We were able to modulate a signal on an electron matter-wave in an interferometer and transmit a short message. It could also be demonstrated that this method has a high level of security against eavesdropper attacks and that a quantum key distribution protocol can be implemented.
Quantum decoherence by Coulomb-interaction:
Quantum applications rely on long coherence times, meaning that the system stays in a quantum state as long as possible. We study the transition from a quantum to a classical state (the so-called decoherence) induced by the Coulomb interaction. This is performed in an interferometer that prepares free electrons in a quantum superposition state close to a normal-, semi- or superconducting surface. We could compare our measurements to different theoretical decoherence models. The studies have significant applications in quantum information science, surface analysis, electron microscopy and the realization of hybrid quantum systems.
Sensor technologies with electron matter-waves:
The extremely short matter-wavelength of electrons allows the development of sensitive quantum sensors for electromagnetic oscillations and mechanical vibrations. We created such sensors with a biprism electron interferometer, a single atom beam source and a delay line detector. External electromagnetic frequencies or vibrations cause a periodic oscillation of the interference fringe pattern. We established a method to apply the high spatial and temporal single particle resolution of the detector and combine it with a second order correlation and Fourier analysis. It allows to reveal the external frequencies and amplitudes with high accuracy due to their perturbation of the interference.