Chemical Control of the Spin-Phonon Interaction to Develop a New Generation of Molecular Quantum Bits

Abstract

Molecular magnetism is a fascinating field critical to the development and understanding of new technologies such as molecular quantum bits and quantum memories. Implementing these materials is fundamentally limited by the rapid decay of populations of electronic spins back to magnetic equilibrium. Because of the small energy scale of paramagnetic interactions, the time a non-equilibrium state can be maintained is governed by the interaction of the electronic spin with the low energy phonon bath of its matrix. Therefore, controlling the strength of this interaction is critical for a new quantum technology. In the weak spin-phonon coupling regime, we can design technology where quantum states can be maintained, even at high temperatures. In the strong spinphonon coupling limit, we can design systems where the properties of the magnet are controlled externally by manipulation of the matrix. There is a large gulf between these lofty goals and our current technological capabilities. Bridging the gap requires a deep understanding of magnetostructural correlations and the impact tuning molecular handles has on the strength of the spin-phonon interaction. This thesis adds new key insights into the nature of the spin-phonon interaction and highlights how it can be controlled along three unique axes. Chapter 1 introduces the field of quantum information science, and the unique and powerful potential transition metal molecular electronic spins have to the field. Chapter 2 highlights the manipulation of local molecular vibrations to minimize the spin-phonon interaction and maximize quantum coherence at higher temperatures. We use these results to establish design principles for creating new high temperature quantum materials. Chapter 3 discusses progress on direct phonon engineering of electron spin systems. We design frameworks of interacting molecular qubits with specific spin topologies to create bulk entangled systems with a desired phonon structure.