  Fast magnetic flux control is a crucial ingredient for circuit quantum
electrodynamics (cQED) systems. So far it has been a challenge to implement
this technology with the high coherence 3D cQED architecture. In this paper we
control the magnetic field inside a superconducting waveguide cavity using a
magnetic hose, which allows fast flux control of 3D transmon qubits on time
scales < 100 ns. The hose is designed as an effective microwave filter to not
compromise the energy relaxation time of the qubit. The magnetic hose is a
promising tool for fast magnetic flux control in various platforms intended for
quantum information processing and quantum optics.
