  We present a microwave quantum refrigeration principle based on the Josephson
effect. When a superconducting quantum interference device (SQUID) is pierced
by a time-dependent magnetic flux, it induces changes in the macroscopic
quantum phase and an effective finite bias voltage appears across the SQUID.
This voltage can be used to actively cool well below the lattice temperature
one of the superconducting electrodes forming the interferometer. The
achievable cooling performance combined with the simplicity and scalability
intrinsic to the structure pave the way to a number of applications in quantum
technology.
