Quantum Channel Simulation in Fidelity is No More Difficult than State Splitting

Characterizing the minimal communication needed for quantum channel simulation is a fundamental task in the quantum information theory. In this paper, we show that, in fidelity, the quantum channel simulation can be directly achieved via quantum state splitting without using a technique known as the de Finetti reduction, and thus provide a pair of tighter one-shot bounds. This opens up new potentials for higher-order analysis. Using the bounds, we also recover the quantum reverse Shannon theorem in a much simpler way.