Cooper, Benjamin KevinI discuss experimental and theoretical results on an LC filtered dc SQUID phase qubit. This qubit is an asymmetric aluminum dc SQUID, with junction critical currents 1.5 and 26.8 μA, on a sapphire substrate. The layout differs from earlier designs by incorporating a superconducting ground plane and weakly coupled coplanar waveguide microwave drive line to control microwave-qubit coupling. I begin with a discussion of quantizing lumped element circuit models. I use nodal analysis to construct a 2d model for the dc SQUID phase qubit that goes beyond a single junction approximation. I then discuss an extension of this ``normal modes'' SQUID model to include the on-chip LC filter with design frequency ∼ 180 MHz. I show that the filter plus SQUID model yields an effective Jaynes-Cummings Hamiltonian for the filter-SQUID system with coupling g / 2 π ∼ 32 MHz. I present the qubit design, including a noise model predicting a lifetime T₁ = 1.2 μs for the qubit based on the design parameters. I characterized the qubit with measurements of the current-flux characteristic, spectroscopy, and Rabi oscillations. I measured T₁ = 230 ns, close to the value 320 ns given by the noise model using the measured parameters. Rabi oscillations show a pure dephasing time T_φ = 1100 ns. The spectroscopic and Rabi data suggest two-level qubit dynamics are inadequate for describing the system. I show that the effective Jaynes-Cummings model reproduces some of the unusual features.enDissertationLow temperature physicsQuantum physicsphase qubitquantum computingSQUIDsuperconducting