  We have begun a series of experiments on mixed bosonic quantum fluids. Our
system is mixed Bose-Einstein condensates in dilute Rb-87. By simultaneously
trapping the atoms in two different hyperfine states, we are able to study the
dynamics of component separation and of the relative quantum phase of two
interpenetrating condensates. Population can be converted from one state to the
other at a rate that is sensitive to the relative phase.
