TITLE: Towards Scalable Quantum Computation: Control and Shuttling of Hole Spin Qubits
Author: David Fernández Fernández - Instituto de Ciencia de Materiales de Madrid (ICMM-CSIC)
Supervised by: Gloria Platero (ICMM-CSIC)
When: January, 28 - 12 PM
Where: Salón de Actos, ICMM
Abstract: Quantum computing has emerged as a powerful paradigm capable of addressing problems that are intractable for classical computers, with applications ranging from simulating quantum matter and materials discovery to secure communication. Among the various hardware platforms under active development, semiconductor spin qubits are particularly attractive due to their compatibility with established microelectronics technology and their potential for large-scale integration. Despite this promise, key challenges remain, including maintaining coherence in noisy solid-state environments, achieving fast and high-fidelity control, and enabling long-distance connectivity between qubits. Overcoming these challenges requires both a detailed understanding of the microscopic physics governing spin qubits and the development of advanced protocols for control and transport.
This thesis addresses these issues through a theoretical study of hole spin qubits in planar semiconductor quantum dots, where strong spin–orbit interaction enables robust and scalable quantum information processing. The work presents a microscopic description of electrons and holes in gated quantum dot arrays using a unified Hamiltonian framework that incorporates Coulomb interactions, interdot tunneling, magnetic coupling, and spin–orbit effects. This approach captures the interplay between charge localization, spin dynamics, and orbital hybridization, providing a direct connection between device-level parameters and effective low-energy qubit models. Different spin-qubit encodings, including single-spin and singlet–triplet qubits, are analyzed, enabling a systematic comparison of control requirements, noise sensitivity, and scalability.
A central theme of this thesis is the investigation of quantum transport in semiconductor quantum dot arrays. Both coherent and incoherent regimes of charge and spin transport are studied, showing how long-range tunneling enables efficient information transfer even in asymmetric configurations. Effective low-energy models capture the essential physics of long-range transport and identify the conditions under which transport blockade is lifted. The interplay between spin–orbit interaction and periodic driving reveals effective magnetic fields that enable electrically driven spin manipulation.<br />\r\nBeyond transport, the thesis develops advanced protocols for spin-qubit manipulation, with emphasis on shortcuts-to-adiabaticity techniques that enable fast operations with high fidelity in realistic noise environments. Finally, shuttling protocols for extended quantum dot arrays are investigated, demonstrating coherent long-distance transfer of single- and two-qubit states and the possibility of performing gate operations during transport using spin–orbit interaction or magnetic field gradients.
