Electron Spin-Based Quantum Sensing in Biomolecular Systems

Author: Totoiu, Christian Alexander

Year: 2026

Degree: Dissertation (Ph.D.)

Advisor: Hadt, Ryan G.

Committee Members: Shapiro, Mikhail G.; Arnold, Frances Hamilton; Rees, Douglas C.; Hadt, Ryan G.

Option: Chemical Engineering

Abstract

Paramagnetic biomolecules bridge the gap between chemical reactivity through redox processes and quantum mechanics through their inherent electron spins. In this way, they provide a rich set of fundamental systems to elucidate complex electron spin dynamics and investigate their potential effects on native biological functions. Particularly, paramagnetic molecules, via the Zeeman effect, are able to act as molecular quantum bits (qubit) in an external magnetic field by generating a two-level system that operates quantum mechanically. The specificity and synthetic control of molecular spin qubits make them attractive targets for quantum sensing applications. Conventional quantum sensing modalities are often solid-state sensors lacking broad tunability, and magnetic resonance techniques rely on abundant nuclear spins for imaging. Conversely, molecular quantum sensors using electron spins offer chemical tunability of both spin coherences via electronic structure and precise targeting for local chemical microenvironments. Two main classes of quantum sensors are described in this work: organic radical-labeled micelles and paramagnetic metalloproteins. The former can be chemically tuned to target specific areas of interest and are active across broad temperature ranges. The latter are found ubiquitously across the kingdoms of life and offer native sensing targets. Across these systems, the advantages of native biomolecular qubits as quantum sensors were demonstrated alongside the capacity to gain fundamental biophysical insight.