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Abstract

The quest towards precise measurement and control of quantum mechanical systems is behind many if not most of the advances in mesoscopic physics in the recent years. This thesis follows that tradition, and describes the first realization of a hybrid circuit integrating electrons on helium (EonHe) with the circuit quantum electrodynamics (cQED) architecture. In this hybrid architecture, the quantized lateral motion of the electrons strongly couples with the transverse electric field inside a high-Q superconducting resonator, enabling sensitive detection and manipulation of the electron's in-plane motion degree of freedom. Such architecture also provide a plausible road map towards using the spin degrees of freedom of the electrons as a quantum memory. Our hope is to establish a novel model system for quantum control and manipulation, where the uncanny similarity between the electron hamiltonian and the strong coulomb interactions could give rise to unparallelly rich quantum phenomena. In our first experiment towards this goal, we demonstrate strong dispersive coupling between $\sim 10^5$ electrons and a superconducting co-planar waveguide resonator. The effort of the second experiment focuses on bringing down this number to just a few electrons in an isolated trap. The CPW resonator was replaced by a quarter-wavelength strip-line resonator with one side terminated by a short (``the tuning fork"). This design changes the microwave mode that is visible to the electron dipole interaction, improves the coupling strength, and opens up the geometry for more sophisticated DC controls isolating an individual electron. The third experiment implements such DC control scheme, and manages to trap just a single electron in a small trap. This small electron trap is defined by multiple DC electrodes near the open-end of the tuning fork. The overall circuit design resembles those seen in the quantum dot community. Much effort was spent on hitting the tight space between the dispersive constraints of the cQED measurement scheme and the increasing complication of the sample. Single or few electron spectra are measured, and we provided an upper estimate on the acoustically broadened electron line-width, together with design changes that reduce the line-width of the electron states.

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