Quantum depolarizing channel

A quantum depolarizing channel is a model for quantum noise in quantum systems. The d {\displaystyle d} -dimensional depolarizing channel can be viewed as a completely positive trace-preserving map Δ λ {\displaystyle \Delta _{\lambda }} , depending on one parameter λ {\displaystyle \lambda } , which maps a state ρ {\displaystyle \rho } onto a linear combination of itself and the maximally mixed state, Δ λ ( ρ ) = ( 1 − λ ) ρ + λ d ( t r ( ρ ) ) I = ( 1 − λ ) ρ + λ d I .

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