Improving dc SQUID Phase Qubit Lifetimes through Increased Isolation from Bias Leads*

The dc SQUID phase qubit has been plagued by a relatively short coherence time, T$_{2}$, and relaxation time, T$_{1}$ (tens of ns). By using a sapphire substrate and small (15 $\mu $m$^{2}$ or less) Al/AlO$_{x}$/Al junctions the performance of the qubit has improved to the point where the impedance of the bias leads is the main source of dissipation and decoherence in the device. We identify the main circuit parameters that effect the isolation (junction capacitance, loop inductance, etc.), and present designs to improve the qubits isolation from the bias leads.