Decoherence of excitonic qubits in Förster coupled quantum dots

Abstract

We investigate phonon-assisted mechanisms which contribute to the decoherence of excitonic qubits in quantum dot systems coupled by a Förster-type transfer process. Using the Fermi Golden Rule, we derive explicit expressions for the relaxation and dephasing times for excitonic qubits interacting with acoustic phonons via both the deformation potential and piezoelectric coupling. The decoherence times computed using the Fermi Golden Rule are consistent with those estimated using Bloch–Redfield theory at interdot tunnelling energies small enough for Markovian theories to be valid. Our results show that renormalization of interdot tunnelling frequencies due to phonon interactions is influenced mainly by bias and lattice temperature in GaAs/AlGaAs quantum dot systems.