  Coherent perfect absorption (CPA) is an interference process associated with
the zeros of the scattering matrix that enables light-with-light interactions
in linear systems, of interest for optical computing, data processing and
sensing. However, the noise properties of CPA remain relatively unexplored.
Here, we demonstrate that CPA thermal noise signals exhibit a unique property:
they are orthogonal to the signals transmitted through the network. In turn,
such property enables a variety of thermal noise management effects, such as
the physical separability of thermal noise and transmitted signals, and
"externally lossless" networks that internally host radiative heat transfer
processes. We believe that our results provide a new perspective on the many
CPA technologies currently under development.
