Overhead for simulating a non-local channel with local channels by quasiprobability sampling

As the hardware technology for quantum computing advances, its possible applications are actively searched and developed. However, such still suffer from noise on devices, in particular when using two-qubit gates whose fidelity is relatively low. One way to overcome this difficulty substitute non-local operations by local ones. Such substitution can be performed decomposing a channel into linear combination of channels simulating original with quasiprobability-based method. In work, we first define quantity that call robustness non-locality, which quantifies cost decomposition. While challenging calculate general channel, give an upper bound unitary providing explicit The decomposition obtained generalizing our previous work application has been restricted certain form unitary. This develops framework resource reduction suitable first-generation devices.