  Various phase shifters and absorbers can be put into the arms of a double
loop neutron interferometer. The mean intensity levels of the forward and
diffracted beams behind an empty four plate interferometer of this type have
been calculated. It is shown that the intensities in the forward and diffracted
direction can be made equal using certain absorbers. In this case the
interferometer can be regarded as a 50/50 beam splitter. Furthermore the
visibilities of single and double loop interferometers are compared to each
other by varying the transmission in the first loop using different absorbers.
It can be shown that the visibility becomes exactly 1 using a phase shifter in
the second loop. In this case the phase shifter in the second loop must be
strongly correlated to the transmission coefficient of the absorber in the
first loop. Using such a device homodyne-like measurements of very weak signals
should become possible.
