  The polarization of light is utilized in many technologies throughout science
and engineering. The ability to transform one state of polarization to another
is a key enabling technology. Common polarization transformers are simple
polarizers and polarization rotators. Simple polarizers change the intensity
depending on the input state and can only output a fixed polarized state, while
polarization rotators rotates the input Stokes vector in the 3D Stokes space.
We demonstrate an all-optical input-agnostic polarization transformer (AI-APT),
which transforms all input states of polarization to a particular state that
can be polarized or partially polarized. The output state of polarization and
intensity depends solely on setup parameters, and not on the input state,
thereby the AI-APT functions differently from simple polarizers and
polarization rotators. The AI-APT is completely passive, and thus can be used
as a polarization controller or stabilizer for single photons and ultrafast
pulses. The AI-APT may open a new frontier of partially polarized ultrafast
optics.
