cQ3D proposes a 48-month program to improve the quantum coherence of superconducting flux qubits using cutting-edge developments in circuit quantum electrodynamics (QED). Beyond the immediate benefit to quantum computing with superconducting circuits, this effort will enable fundamental physics, such as the investigation of non-equilibrium quasiparticles in superconductors. Finally, it will pave the way for hybrid quantum computing with superconducting flux qubits coupled to electronic spins.cQ3D will first focus on achieving strong coupling of flux qubits to three-dimensional (3D) superconducting resonators. The evolution from 2D to 3D circuit QED reduces the contribution of lossy metal and dielectric surfaces and interfaces to qubit energy decay by storing this energy primarily in vacuum. By providing a means to control, couple and measure flux qubits in a near-perfect electromagnetic environment with minimal additional circuitry, we aim to surpass and elucidate current limits to coherence in flux qubits. In particular, this pursuit may uncover a contribution from non-thermal distributions of quasiparticles, as predicted by recent theory. The developed architecture will finally be used to couple small ensembles of electronic spins to flux qubits and/or to resonators using flux qubits as a quantum interconnect.A CIG grant will facilitate the local and international integration of my new group at TU Delft by creating opportunities for collaboration and discussion with several faculty in the Kavli Institute of Nanoscience, and facilitating research complementing that of my international collaborators. Simultaneously, this grant will enable key infrastructure developments in fabrication and simulation that will impact my group beyond the tenure-track race.