  The study of quantum channels is the fundamental field and promises wide
range of applications, because any physical process can be represented as a
quantum channel transforming an initial state into a final state. Inspired by
the method performing non-unitary operator by the linear combination of unitary
operations, we proposed a quantum algorithm for the simulation of universal
single-qubit channel, described by a convex combination of 'quasiextreme'
channels corresponding to four Kraus operators, and is scalable to arbitrary
higher dimension. We demonstrate the whole algorithm experimentally using the
universal IBM cloud quantum computer and study properties of different qubit
quantum channels. We illustrate the quantum capacity of the general qubit
quantum channels, which quantifies the amount of quantum information that can
be protected. The behaviour of quantum capacity in different channels reveal
which types of noise processes can support information transmission, and which
types are too destructive to protect information. There is a general agreement
between the theoretical predictions and the experiments, which strongly
supported our method. By realizing arbitrary qubit channel, this work provides
a universal way to explore various properties of quantum channel and novel
prospect of quantum communication.
