How important are those fields of chemistry in biotechnology and medicinal chemistry
Your question is broad and these chemistry which you have pointed out in your question is interlinked (Quantum ,Physical and Computational chemistry). The best way which I can explain this question is by giving links to main research carried out using these chemistry in biological science.

The study of quantum mechanics in photosynthesis is one such area and this nature paper(Nature 446, 782-786 (12 April 2007) is about that research

the highlights of the paper is the evidence for wavelike energy transfer through quantum coherence in photosynthetic systems


  two-dimensional electronic spectroscopy investigations of the FMO
  bacteriochlorophyll complex, and obtain direct evidence for remarkably
  long-lived electronic quantum coherence playing an important part in
  energy transfer processes within this system. The quantum coherence
  manifests itself in characteristic, directly observable quantum
  beating signals among the excitons within the Chlorobium tepidum FMO
  complex at 77 K. This wavelike characteristic of the energy transfer
  within the photosynthetic complex can explain its extreme efficiency,
  in that it allows the complexes to sample vast areas of phase space to
  find the most efficient path.


Other useful links

Nature 431, 256-257 (16 September 2004)

Nature 446, 740-741 (12 April 2007)