  Superconducting microwave circuits show great potential for practical quantum
technological applications such as quantum information processing. However,
fast and on-demand initialization of the quantum degrees of freedom in these
devices remains a challenge. Here, we experimentally implement a tunable heat
sink that is potentially suitable for the initialization of superconducting
qubits. Our device consists of two coupled resonators. The first resonator has
a high quality factor and a fixed frequency whereas the second resonator is
designed to have a low quality factor and a tunable resonance frequency. We
engineer the low quality factor using an on-chip resistor and the frequency
tunability using a superconducting quantum interference device. When the two
resonators are in resonance, the photons in the high-quality resonator can be
efficiently dissipated. We show that the corresponding loaded quality factor
can be tuned from above $10^5$ down to a few thousand at 10 GHz in good
quantitative agreement with our theoretical model.
