  Strongly squeezed states of light are a key technology in boosting the
sensitivity of interferometric setups, such as in gravitational-wave detectors.
However, the practical use of squeezed states is limited by optical loss, which
reduces the observable squeeze factor. Here we experimentally demonstrate that
introducing squeezed states in additional, higher-order spatial modes can
significantly improve the observed nonclassical sensitivity improvement when
the loss is due to mode-matching deficiencies. Our results could be directly
applied to gravitational-wave detectors, where this type of loss is a major
contribution.
