Alp Sipahigil (Advisor)

Ultralong lifetimes of silicon nanomechanical resonators at cryogenic temperatures and microwave frequencies make them promising resources in quantum engineering. In this work, we propose a nanomechanical qubit achieving strong single-phonon level anharmonicity of 5 MHz without the need for coupling to an ancillary qubit of a hybrid quantum architecture. This qubit design combines a nano-machined silicon cantilever brought in proximity to a silicon surface using microelectromechanical actuators. The surface forces between the cantilever and the silicon surface provide an effective...

Superconducting quantum circuits are leading candidates for quantum computing. Scaling up these systems for practical applications will require compact coherent qubits that store the quantum states, high fidelity quantum gates that process them, and a scalable architecture that can accommodate complex error correction circuits. Meeting such requirements is mainly impeded by the unavoidable presence of two-level systems (TLS), which act as a decoherence source that results in the loss of quantum information via phonon emission. In this project, we engineer superconducting circuits...