  We present new techniques for inertial-sensing atom interferometers which
produce multiple phase measurements per experimental cycle. With these
techniques, we realize two types of multiport measurements, namely quadrature
phase detection and real-time systematic phase cancellation, which address
challenges in operating high-sensitivity cold-atom sensors in mobile and field
applications. We confirm experimentally the increase in sensitivity due to
quadrature phase detection in the presence of large phase uncertainty, and
demonstrate suppression of systematic phases on a single shot basis.
