Dividing quantum channels

Michael M. Wolf, J. Ignacio Cirac

Research output: Contribution to journalArticlepeer-review

223 Scopus citations


We investigate the possibility of dividing quantum channels into concat-enations of other channels, thereby studying the semigroup structure of the set of completely-positive trace-preserving maps. We show the existence of 'indivisible' chan-nels which can not be written as non-trivial products of other channels and study theset of 'infinitesimal divisible' channels which are elements of continuous completely positive evolutions. For qubit channels we obtain a complete characterization of the sets of indivisible and infinitesimal divisible channels. Moreover, we identify those channels which are solutions of time-dependent master equations for both positive and completely positive evolutions. For arbitrary finite dimension we prove a representation theorem for elements of continuous completely positive evolutions based on new results on deter-minants of quantum channels and Markovian approximations.

Original languageEnglish
Pages (from-to)147-168
Number of pages22
JournalCommunications in Mathematical Physics
Issue number1
StatePublished - Apr 2008
Externally publishedYes


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