  Multi-loop matter-wave interferometers are essential in quantum sensing to
measure the derivatives of physical quantities in time or space. Because
multi-loop interferometers require multiple reflections, imperfections of the
matter-wave mirrors create spurious paths that scramble the signal of interest.
Here we demonstrate a method of adjustable momentum transfer that prevents the
recombination of the spurious paths in a double-loop atom interferometer aimed
at measuring rotation rates. We experimentally study the recombination
condition of the spurious matter waves, which is quantitatively supported by a
model accounting for the coherence properties of the atomic source. We finally
demonstrate the effectiveness of the method in building a cold-atom gyroscope
with a single-shot acceleration sensitivity suppressed by a factor of at least
50. Our study will impact the design of multi-loop atom interferometers that
measure a single inertial quantity.
