UC Santa Barbara

This thesis focuses on the growth and characterization of compounds, devices, and structures for applications in Quantum computing. Quantum computing leverages the principles of quantum mechanics to process information, promising exponential speedup for certain problems. Here, we are interested in two branches - Superconducting and Topological Quantum Computing. Superconducting quantum computing uses circuits cooled to near absolute zero to create and manipulate qubits with high fidelity. Topological quantum computing, on the other hand, exploits the properties of quasiparticles called anyons to form qubits that are inherently resistant to errors, offering the potential for more stable and scalable quantum systems.

Motivated by recent advancements highlighting Ta as a promising material in low-loss superconducting circuits and showing long coherence times in superconducting qubits, we have chosen Tantalum as the superconductor. Here, we have explored the possibility of growth of Ta/Ta2O5/Ta Josephson Junctions for transmon qubits. The growth of such junctions was done at low temperatures using the LT-MBE.

Topological insulators can be used in topological quantum computing by exploiting their edge states, which are protected by time-reversal symmetry and are predicted to be robust against local perturbations. This protection reduces the error rates in quantum computations, enhancing the stability and coherence of qubits. Here, we demonstrate the growth of α-Sn on InSb(001) in ultrathin limit using tensile strain which is a potential topological insulator. The films were characterized electrically in a cryogenic setup using a Hall bar geometry. Fabrication of the hall bars using low-temperature processing techniques has also been demonstrated which ensures there is no phase transition from α to β-Sn.