In semiconductor-based quantum information devices, the main focus is recently put on manipulation of discrete quantum states confined in artificial atoms. However, such localized qubits require vast infrastructure, because one needs hardware for all billions of qubits. In this project, we manipulate delocalized qubits based on electron waves in semiconductor nanostructures. In order to achieve high fidelity and high quality factor, we develop new designs of electron wave interferometers combined with quasi-particle excitations that have macroscopic coherence length. Since quasi-particle qubits are created on-demand from the Fermi sea of the electron source, the number of qubits is also set on-demand. The hardware size can thus be significantly reduced. We also control interaction between localized and delocalized quantum systems to construct hybrid systems. The concepts and technologies developed for delocalized qubits will bring a paradigm shift in quantum architectures.