It is known by the no-cloning theorem that constructing a machine that is able to clone an arbitrary quantum state is impossible. However, if the copying is assumed not to be perfect, then universal quantum cloning machines can be generated, being able to create imperfect copies of arbitrary quantum states where the original state and the copy have a certain degree of fidelity that depends on the machine. I came across the paper Quantum copying: Beyond the no-cloning theorem by Buzek and Hillery where this kind of universal quantum cloning machine is presented. However, this paper is from 1996 and I am not aware if some advances in this kind of machines have been done yet.
Consequently, I would like to know if someone does know if any advances in such kind of cloning machines have been done since then, that is, machines whose fidelity is better than the one presented in such paper, or the methods are less complex ... Additionally, it would be also interesting to obtain references about any useful application that such machines present if there is any.