  Coherent perfect absorption (CPA) was introduced as a classical optics
phenomenon of a standing-wave absorption by a subwavelength film. In this
paper, we develop a theory of CPA of quantized standing waves taking account of
a subwavelength thickness of the absorber. This approach allows us to merge all
known quantum effects of CPA under a single theory and introduce other regimes
of CPA including CPA of NOON states with arbitrary number of entangled photons,
orthogonally squeezed vacuum states, continuous variable entangled states, and
Schr\"odinger cat states. Detailed analysis of the quantum regime of CPA sheds
light on fundamental aspects of quantum light dissipation and its practical
implementation in quantum optics and quantum information.
