  An SU(1,1) interferometer replaces the beamsplitters in a Mach-Zehnder
interferometer with nonlinear interactions and offers the potential of
achieving high phase sensitivity in applications with low optical powers. We
present a novel variation in which the second nonlinear interaction is replaced
with balanced homodyne detection. The phase-sensing quantum state is a two-mode
squeezed state produced by seeded four-wave-mixing in Rb vapor. Measurements as
a function of operating point show that even with $\approx35~\%$ loss this
device can surpass the standard quantum limit by 4~dB.
