Decoherence of a spin-valley qubit in a MoS2 quantum dot

Transition metal dichalcogenide (TMD)-based quantum dots (QDs) have proven to be a successful and promising device for physically implementing electron spin-valley based qubits. Although the electron spin in a TMDs monolayer semiconductor QD can be isolated and controlled with high precision, decoherence occurs due to unavoidable coupling with the surrounding environment, such as nuclear spin environments. In this paper, using an exact master equation (ME) of spin qubit dynamics coupled to a nuclear spin bath in terms of hyperfine interaction (HI), we have investigated the controllability of dynamics processes with varying degrees of non-Markovianity. In large magnetic fields, we show that pure spin or valley qubits can be created. We calculate the loss of fidelity due to the Overhauser field of HI in a wide range of nuclear spin N . In this context, we prove that this field restricts the decoherence process of the central electron spin, which can regain its coherence. Finally, we discuss how the coherence of the spin qubit remains robust for large N .