Quantum Channel

A Trace Preserving Dynamical Map $\Phi$. The trace preserving property means that for any Density Operator $\rho$, which by definition has Trace 1, the Density Operator $\Phi [\rho ]$ also has Trace 1.

Quantum Channels are often referred to as CPTP Maps, since they are Completely Positive Trace Preserving Dynamical Maps.