Narrowing of the Overhauser field distribution in a GaAs double quantum dot

For GaAs spin qubits all essential operations for QI have been demonstrated and coherence times are increasing. However, coherent control is still, like in many other electron spin qubit systems, impaired by the fluctuating nuclear spin bath of the host material. Previous experiments have shown dynamic nuclear polarization with feedback to significantly prolong de inhomogeneous dephasing time T2∗ by narrowing the distribution of nuclear Overhauser field fluctuations.

In this talk I present a model relating the achievable narrowing of the Overhauser field to both the pump rate and the noise magnitude. Furthermore, I propose an alternative feedback scheme using electron dipole spin resonance, which promises T2∗ values on the order of microseconds. Finally I show the steps that have been undertaken towards implementation.