Self-quenching of nuclear spin dynamics in the central spin problem

Abstract

We consider, in the framework of the central spin s = 1/2 model, driven dynamics of two electrons in a double quantum dot subject to hyperfine interaction with nuclear spins and spin-orbit coupling. The nuclear subsystem dynamically evolves in response to Landau-Zener singlet-triplet transitions of the electronic subsystem controlled by external gate voltages. Without noise and spin-orbit coupling, subsequent Landau-Zener transitions die out after about 10 4 sweeps, the system self-quenches, and nuclear spins reach one of the numerous glassy dark states. We present an analytical model that captures this phenomenon. We also account for the multi-nuclear-specie content of the dots and numerically determine the evolution of around 10 7 nuclear spins in up to 2 × 10 5 Landau-Zener transitions. Without spin-orbit coupling, self-quenching is robust and sets in for arbitrary ratios of the nuclear spin precession times and the waiting time between Landau-Zener sweeps as well as under moderate noise. In the presence of spin-orbit coupling of a moderate magnitude, and when the waiting time is in resonance with the precession time of one of the nuclear species, the dynamical evolution of nuclear polarization results in stroboscopic screening of spin-orbit coupling. However, small deviations from the resonance or strong spin-orbit coupling destroy this screening. We suggest that the success of the feedback loop technique for building nuclear gradients is based on the effect of spin-orbit coupling.

Characterization of an exchange-based two-qubit gate for resonant exchange qubits

“…We calibrated our simulations to reflect an unsuppressed Overhauser field in GaAs/AlGaAs heterostructures. It is possible to suppress the Overhauser field fluctuations using dynamic nuclear polarisation [41][42][43], which can reduce the standard deviation of the field fluctuations by several orders of magnitude (e.g. [38]).…”