  Three-dimensional (3D) superconducting microwave cavities with large mode
volumes typically have high quality factors ($>10^6$). This is due to a reduced
sensitivity to surface dielectric losses, which is the limiting source of
dissipation in two-dimensional transmission line resonators. In recent years,
3D microwave cavities have been extensively used for coupling and interacting
with superconducting quantum bits (qubits), providing a versatile platform for
quantum information processing and hybrid quantum systems. A current issue that
has arisen is that 3D superconducting cavities do not permit magnetic field
control of qubits embedded in these cavities. In contrast, microwave cavities
made of normal metals can be transparent to magnetic fields, but experience a
much lower quality factor ($\sim 10^4$), which negates many of the advantages
of the 3D architecture. In an attempt to create a device that bridges a gap
between these two types of cavities, having magnetic field control and high
quality factor, we have created a hybrid 3D cavity. This new cavity is
primarily composed of aluminium but also contains a small copper insert. We
measured the internal quality factor of the hybrid cavity to be $102000$, which
is an order of magnitude improvement over all previously tested copper
cavities. An added benefit to that our hybrid cavity possesses is that it also
provides an improved thermal link to the sample that superconducting cavities
alone cannot provide. In order to demonstrate precise magnetic control within
the cavity, we performed spectroscopy of three superconducting qubits placed in
the cavity, where individual control of each qubit's frequency was exerted with
small wire coils attached to the cavity. A large improvement in quality factor
and magnetic field control makes this 3D hybrid cavity an attractive new
platform for circuit quantum electrodynamics experiments.
