Control of dephasing and phonon emission in coupled quantum dots

We predict that phonon subband quantization can be detected in the nonlinear electron current through double quantum dot qubits embedded into nanosize semiconductor slabs, acting as phonon cavities. For particular values of the dot level splitting Δ, piezoelectric or deformation potential scattering is either drastically reduced as compared to the bulk case, or strongly enhanced due to phonon van Hove singularities. By tuning Δ via gate voltages, one can either control dephasing, or strongly increase emission into phonon modes with characteristic angular distributions.