  A tunable and balanced heat interferometer is proposed and analyzed. The
device consists of two superconductors linked together to form a double-loop
interrupted by three Josephson junctions coupled in parallel. Both
superconductors are held at different temperatures allowing the heat currents
flowing through the structure to interfere. As we show here, thermal transport
is coherently modulated through the application of a magnetic flux.
Furthermore, such modulation can be tailored at will through the application of
an extra control flux. In addition we show that, provided a proper choice of
the system parameters, a fully balanced interferometer is obtained. The latter
means that the phase-coherent part of heat current can be controlled to the
extent of being fully suppressed. Such a device allows for a versatile
operation appearing, therefore, as an attractive key to the onset of
low-temperature coherent caloritronic circuits.
