  Quantum correlations in $\psi(3770) \to D^0\bar{D}^0$ provide unique access
to information about strong phase differences. Precision determination of the
CKM phase $\gamma/\phi_3$ via $B \to D K$ decays depends upon constraints on
charm mixing amplitudes, measurements of doubly-Cabibbo suppressed amplitudes
and relative phases, and studies of correlated charmed meson decays tagged by
flavor or CP eigenstates. CP-tagged $D^0 \to K^-\pi^+\pi^-\pi^+$ decays and
CP-tagged $D^0 \to K^0_S\pi^+\pi^-$ Dalitz plots are only available at CLEO-c.
Using the 818 pb$^{-1}$ CLEO-c data sample produced by the Cornell Electron
Storage Ring (CESR) at $\sqrt{s} = 3.77$ GeV, we perform analyses of these
decays. We describe the techniques used to measure the $D$-decay parameters,
and the CLEO-c impact on measurements of $\gamma/\phi_3$.
