Ab Initio Design of\nMolecular Qubits with Electric\nField Control

Current scalable quantum computers require large footprints\nand\ncomplex interconnections due to the design of superconducting qubits.\nWhile this architecture is competitive, molecular qubits offer a promising\nalternative due to their atomic scale and tuneable properties through\nchemical design. The use of electric fields to precisely, selectively\nand coherently manipulate molecular spins with resonant pulses has\nthe potential to solve the experimental limitations of current molecular\nspin manipulation techniques such as electron paramagnetic resonance\n(EPR) spectroscopy. EPR can only address a macroscopic ensemble of\nmolecules, defeating the inherent benefits of molecule-based quantum\ninformation. Hence, numerous experiments have been performed using\nEPR in combination with electric fields to demonstrate coherent spin\nmanipulation. In this work, we explore the underlying theory of spin-electric\ncoupling in lanthanide molecules, and outline ab initio methods to\ndesign molecules with enhanced electric field responses. We show how\nstructural distortions arising from electric fields generate coupling\nelements in the crystal field Hamiltonian within a Kramers doublet\nground state and demonstrate the impact of molecular geometry on this\nphenomenon. We use perturbation theory to rationalize the magnetic\nand electric field orientation dependence of the spin-electric coupling.\nWe use pseudo-symmetry point groups to decompose molecular distortions\nto understand the role that symmetry has on spin-electric coupling.\nFinally, we present an analytical electric field model of structural\nperturbations that provides large savings in computational expense\nand allows for the investigation of experimentally accessible electric\nfield magnitudes which cannot be accessed using common ab initio methods.