Theoretical Study on Robust Manipulation of Coupled Quantum Dot Spin Qubits

Description

Quantum information processing is presently an active research area due to its potential in technological applications that may be far more powerful than present day electronics.A qubit, or quantum bit, can be encoded in the spin states of electrons confined in semiconductor quantum dots. Although reasonably long coherence times and high control fidelities have been demonstrated in spin qubits, challenges remain for their application in scalable quantum information processing.There are two major hurdles in the field: decoherence and scalability. The quantum information carried by spin qubits inevitably deteriorates through interactions with the environment, causing decoherence. Various control techniques are developed to combat such forces, including the Dynamically Corrected Gates. On the other hand, problems have been identified to concur with the scaling up of spin qubits, the most important ones being the gate crosstalk and leakage.In this project, we will develop theoretical methodologies that can help in overcoming these hurdles. In particular, we will benchmark existing control protocols under experimentally realistic noises, and will optimize them so as to facilitate their applications in laboratories. We will quantify destructive factors of gate crosstalk and leakage in a scaled-up spin qubit array and will search for effective and practical ways to reduce these errors. We will develop a comprehensive theory on multi-electron multi-qubit devices through microscopic calculations, including a quantitative understanding on how charged impurities may be screened by the multi-electron states. Finally, we will further the studies to a wider range of realizations of spin qubits including the resonant-exchange qubit and hybrid qubit.The results of this research are expected to bridge the gap between theoretical control protocols and their experimental realization, and will provide new insights on operating a spin qubit array in a noise-resistant manner. Successful completion of this project will contribute to a more comprehensive theoretical picture of the robust manipulation of coupled quantum dot spin qubits, and will be of great help in the on-going effort using them for scalable fault-tolerant quantum information processing.