Open quantum system description of singlet-triplet qubits in quantum dots
We develop a theoretical model to describe the dissipative dynamics of singlet-triplet (S-T_0) qubits in GaAs quantum dots. Using the concurrence experimentally obtained as a guide, we show that each logical qubit is coupled to its own environment because the decoherence effect can be described by independent dephasing channels. Given the correct description of the environment, we study the dynamics of concurrence as a function of the temperature, the constant coupling between the system and the environment, the preparation time, and the exchange coupling. Although the reduction of the environment coupling constant modifies the entanglement dynamics, we demonstrate that temperature emerges as a crucial variable and a variation of millikelvins significantly modifies the generation of entangled states. Furthermore, we show that the exchange coupling together with the preparation time strongly affects the entanglement dissipative dynamics.