Tunable Coupling between Two Resonators Controlled by a Flux Qubit: the Quantum Switch

In the field of quantum information processing, superconducting circuits have become a well-established platform. In particular, systems consisting of a few qubits and/or harmonic oscillator circuits have been investigated. When scaling up these systems, it seems practical to aim for active guidance elements allowing for a directed transmission of quantum signals. One way to achieve this is by implementing switchable coupling between two microwave resonators. We show experimental progress on two superconducting transmission line resonators, where a superconducting flux qubit mediates a controllable coupling - the Quantum Switch. We show an experimental characterization of such a device and discuss spectroscopic evidence for the switching behavior.\\[4pt] We acknowledge support from the DFG via SFB~631, the German excellence initiative via NIM, and EU projects CCQED, SOLID and PROMISCE, the Basque Foundation for Science, Basque Government IT472-10, and Spanish MICINN FIS2009-12773-C02-01, DZ granted by ARAID