Author ORCID Identifier
Date of Award
3-2025
Document Type
Thesis (Ph.D.)
Department or Program
Physics and Astronomy
First Advisor
Chandrasekhar Ramanathan
Abstract
Lattices of dipolar coupled nuclear spins in natural crystals are large, interacting quantum systems -- ideal platforms to simulate non-equilibrium many-body dynamics. Using the magnetic resonance toolkit, which includes Dynamic Nuclear Polarization (DNP), Hamiltonian engineering, and multiple-quantum Nuclear Magnetic Resonance (NMR) experiments, we study aspects of coherent control, manipulation, and readout of the complex dynamics of the spin system in NMR quantum simulation.
First, applying Hamiltonian engineering sequences, we control the system evolution. Specifically, we use a combination of numerical simulations and NMR experiments on adamantane to evaluate and compare the performance of several known sequences that aim to suppress the magnetic dipolar interaction between spins. The effect of sequence parameters and control errors on sequence performance is explored and the presence of local disorder is established, perhaps unsurprisingly, as a distinguishing factor in the decoupling efficiency of spectroscopic and time-suspension sequences. Additionally, we use time-reversal multiple-quantum experiments to probe the growth of multi-spin correlations involving large clusters of spins and explore the ability of time-suspension sequences to protect these correlated initial states.
Furthermore, we study a Hamiltonian with tuneable interactions and disorder that can be engineered from the natural Hamiltonian of a heteronuclear NMR quantum simulator. Disorder plays a central role in determining the thermalization properties and dynamics of quantum Hamiltonians. We use numerical simulations of small 1D systems to demonstrate the possibility of a transition of the Hamiltonian dynamics from thermalizing to non-thermalizing behavior at high values of disorder. This transition is reflected in the change in behavior of multiple metrics of quantum thermalization and information scrambling including eigenstate entanglement, statistics of the eigenspectrum, entanglement dynamics, and growth of an out-of-time-ordered commutator.
Finally, we also show DNP to be a potential initial state preparation method in NMR quantum simulation that cools the nuclear spins to access the lower energy levels of the system. This is achieved by polarization transfer from electronic spins under resonant microwave excitation. We demonstrate high nuclear polarization and NMR signal enhancement of $^{13}$C spins in diamond using microwave irradiation of the substitutional nitrogen (P1) centers.
Recommended Citation
Joseph, Linta, "Quantum Control and Simulation Using Hamiltonian Engineering in Solid-State NMR" (2025). Dartmouth College Ph.D Dissertations. 379.
https://digitalcommons.dartmouth.edu/dissertations/379
