Surface acoustic waves (SAWs) are mechanical waves that travel along the surface of a material and find many applications in modern technologies due to the ease of excitation on piezoelectric... Show moreSurface acoustic waves (SAWs) are mechanical waves that travel along the surface of a material and find many applications in modern technologies due to the ease of excitation on piezoelectric substrates via interdigital transducers (IDTs). For example, they are used in telecommunications to create ultra-high-frequency electronic filters. Due to their long coherence times and their ability to interact with many different quantum systems, SAWs are also used in quantum physics research, where they can couple to a variety of two-level systems, such as superconducting qubits, NV centers, and quantum dots. In this thesis, we work with SAW cavities at GHz frequencies on GaAs. First, we develop a fiber-based scanning Michelson interferometer to image the acoustic field distribution inside the cavity. With this unique setup, we can disentangle complex transverse-mode profiles and image spurious bulk acoustic waves, enabling a novel way to optimize SAW devices. Next, we observe for the first time the dynamic Talbot effect from a SAW oscillating grating. The demonstration of this effect enables a new, non-interferometric way to measure surface acoustic waves. Finally, we develop an actively stabilized open-access optical microcavity with a mechanical stability of a few picometers when operated in a closed-cycle cryostat. The combination of this novel setup with a SAW cavity will enable single phonon detection. Show less
Nuclear magnetic resonance force microscopy (MRFM) is a technique which combines magnetic resonance imaging (MRI) with scanning probe microscopy (SPM). The final goal is to develop this technique... Show moreNuclear magnetic resonance force microscopy (MRFM) is a technique which combines magnetic resonance imaging (MRI) with scanning probe microscopy (SPM). The final goal is to develop this technique to such a level that the atomic structure of a virus or protein can be revealed by this microscope. This thesis shows nuclear magnetic resonance force measurements on copper in which the interaction of the magnetic moments of the nuclei of copper with a magnetic cantilever has delivered a detectable signal at a temperature of 50 millikelvin. Furthermore, we show measurements, which support a new theory where at low magnetic field and low temperature, non contact friction between the magnetic cantilever and paramagnetic electron spins is described. These measurements were enabled by technical improvements such as vibration reduction in a cryogen free dilution refrigerator. As a benchmark for the low vibration, we show atomic resolution scanning tunneling microscopy at 15 millikelvin temperature on graphite. We also show a method to create small magnets for MRFM from a thin magnet film. With these small magnets the field gradient and therefore the sensitivity may be significantly enhanced. Show less
