Investigating Coherence with Josephson Phase Qubits Ray Simmonds NIST, Boulder, CO   Over the last few years, Josephson junction based quantum bits have shown great promise for quantum computing. Although the origin of dominant decoherence mechanisms remains unknown, we have developed superconducting phase qubits with coherence times long enough to confirm that we do have basic control over single qubits. These experiments have revealed previously unknown two state microwave resonators within the qubit Josephson junction itself. Furthermore, we have developed measurement techniques fast enough to resolve coupled interactions between our fabricated qubit and a single two-level resonator. Remarkably, these defects have helped to lead the way to performing an experiment whereby two superconducting phase qubits are coupled using a simple capacitor. Thus far, we have successfully shown, for the first time, the ability to simultaneously measure, in the time domain, the coupled interactions of two phase qubits. In order for further progress, we must increase single qubit coherence by sufficiently isolating them from any environmental degrees of freedom including material defects. Recently, we have investigated a number of different phase qubit design geometries in order to identify what, where, and how environmental degrees of freedom couple to individual qubits. These measurements will help to improve the operation of future qubit systems.