UC Santa Barbara

In many-body localized (MBL) systems, entanglement propagates throughout the system despite the absence of transport.

Early experiments have relied on population measurements to indirectly probe these entanglement dynamics.

However, because the entanglement results from phase relationships between localized orbitals, it is more naturally probed with phase sensitive algorithms and measurement.

In this thesis, we use an array of nearest neighbor coupled superconducting qubits to introduce phase sensitive protocols to the experimental study of MBL systems.

We establish that system is MBL by demonstrating disorder induced ergodicity breaking and the presence of effective nonlocal interactions.

We then use density matrix reconstructions to observe the hallmark slow growth of entanglement and provide a site-resolved spatial and temporal map of the developing entanglement.

We also inspect the capacity of the MBL phase to preserve quantum correlations by observing the decay of distillable entanglement when Bell pair embedded in an MBL environment and dephased by remote excitation.

In superconducting quantum processors, such as that used in the MBL study above, dissipation leads to computational errors and must be minimized.

To that end, we also describe coherence engineering experiments in terms of the low power internal quality factor Qi of coplanar waveguide (CPW) resonators,

a figure of merit characterizing dissipation in the quantum computing regime.

We investigate titanium nitride as a superconducting base metal for quantum circuits.

By optimizing the deposition conditions, we achieve a record low-power Qi in CPW resonators.

We also characterize the dielectric loss due to flux trapping hole arrays.

Since flux traps are commonly used to prevent magnetic vortex formation and dielectric loss is a limiting dissipation mechanism,

it is important to estimate the contribution of flux traps to the dielectric dissipation budget.

We find that for reasonable hole patterns the dielectric loss can be small while preventing vortex formation.