  We demonstrate gate control of electronic heat flow in a thermally-biased
single-quantum-dot junction. Electron temperature maps taken in the immediate
vicinity of the junction, as a function of the gate and bias voltages applied
to the device, reveal clearly defined Coulomb diamond patterns revealing a
maximum heat transfer right at the charge degeneracy point. The non-trivial
bias and gate dependence of this heat valve results from both the quantum
nature of the dot at the heart of device and its strong coupling to leads.
