/usr/include/ql/experimental/inflation/ is in libquantlib0-dev 1.7.1-1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/ql/experimental/inflation/all.hpp
/usr/include/ql/experimental/inflation/cpicapfloorengines.hpp
/usr/include/ql/experimental/inflation/cpicapfloortermpricesurface.hpp
/usr/include/ql/experimental/inflation/genericindexes.hpp
/usr/include/ql/experimental/inflation/interpolatedyoyoptionletstripper.hpp
/usr/include/ql/experimental/inflation/kinterpolatedyoyoptionletvolatilitysurface.hpp
/usr/include/ql/experimental/inflation/piecewiseyoyoptionletvolatility.hpp
/usr/include/ql/experimental/inflation/polynomial2Dspline.hpp
/usr/include/ql/experimental/inflation/yoycapfloortermpricesurface.hpp
/usr/include/ql/experimental/inflation/yoyinflationoptionletvolatilitystructure2.hpp
/usr/include/ql/experimental/inflation/yoyoptionlethelpers.hpp
/usr/include/ql/experimental/inflation/yoyoptionletstripper.hpp