Coupling quantum circuits to magnetic molecular qubits

TL;DR

This thesis investigates coupling magnetic molecules, especially Single Molecule Magnets, to superconducting quantum circuits to advance quantum computing, including experimental tests and device design improvements.

Contribution

It introduces methods for coupling SMMs to resonators, evaluates their suitability as qubits, and designs nanometric constrictions to enhance single-spin coupling.

Findings

Successful broadband and EPR spectroscopy measurements of magnetic samples.

Design and testing of nanometric constrictions improve coupling efficiency.

Comparison shows constricted resonators outperform unmodified ones.

Abstract

This thesis explores the coupling of magnetic systems to quantum circuits in the context of quantum computing applications. In particular we study the coupling of superconducting coplanar waveguide resonators to Single Molecule Magnets (SMMs) . The combination of approaches from the fields of Cavity Quantum electrodynamics (QED) and Circuit QED with those from the field of molecular magnetism con provide unique opportunities for quantum computing. We investigate the necessary conditions for coupling single spins and spin ensembles to resonators and what characteristics SMMs should have in order to provide interesting alternatives as quantum bits. We present test measurements of several magnetic samples using both broadband spectroscopy with open waveguides and EPR spectroscopy using coplanar waveguide resonators. We also design, fabricate, and test nanometric constrictions in superconducting resonators with the objective of improving their coupling to single spins. We evaluate the performance of these constricted resonators in comparison to unmodified resonators.