Spin and entanglement dynamics in double quantum dots due to hyperfine interaction: A homogenous coupling approach

Quantum dot spin qubits are among the most promising and most intensively investigated building blocks of possible future solid state quantum computation systems. One of the major limitations of the decoherence time of the confined electron spin is its interaction with surrounding nuclear spins by means of hyperfine interaction. Apart from this adverse aspect, hyperfine interaction can act as a ressource of quantum information processing. For the above reasons it is of key interest to understand the hyperfine induced spin dynamics. We consider the hyperfine interaction in a double quantum dot in zero magnetic field. We give an exact solution of the model for homogenous hyperfine coupling constants and derive the dynamics therefrom. By a detailed investigation of the short time spin dynamics we calculate the decoherence time, which turns out to be in very good agreement with experimental data.