Aligning Spatial Frames Through Quantum Channels
  We review the optimal protocols for aligning spatial frames using quantum systems. The communication problem addressed here concerns a type of information that cannot be digitalized. Asher Peres referred to it as "unspeakable information". We comment on his contribution to this subject and give a brief account of his scientific interaction with the authors. 
E. Bagan and R. Munoz-Tapia