All unital qubit channels are $4$-noisy operations

Abstract

We show that any unital qubit channel can be implemented by letting the input system interact unitarily with a $4$-dimensional environment in the maximally mixed state and then tracing out the environment. We also provide an example where the dimension of such an environment has to be at least $3$.

arXiv comment8 pages, no pictures

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Cited by in corpus (3)

• Non-closure of quantum correlation matrices and factorizable channels that require infinite dimensional ancilla
• The Quantum Monadology
• Mixing of quantum states under Markovian dissipation and coherent control