Editing Quantum channel (section)

== Bistochastic quantum channel ==
A bistochastic quantum channel is a quantum channel <math>\Phi(\rho)</math> that is [[unital map|unital]],<ref>{{cite journal|first1=John A. |last1=Holbrook |first2=David W. |last2=Kribs |first3=Raymond |last3=Laflamme |title=Noiseless Subsystems and the Structure of the Commutant in Quantum Error Correction |journal=Quantum Information Processing |volume=2 |number=5 |pages=381–419 |date=October 2003 |arxiv=quant-ph/0402056 |doi=10.1023/B:QINP.0000022737.53723.b4|bibcode=2003QuIP....2..381H }}</ref> i.e. <math>\Phi(I) = I</math>. These channels include unitary evolutions, convex combinations of unitaries, and (in dimensions larger than 2) other possibilities as well.{{sfn|Bengtsson|Życzkowski|2017|pages=288–289}}