Buzek-Hillery cloning revisited using the bures metric and trace norm - art. no. 052313

Buzek and Hillery have recently analyzed the possibility of cloning imperfe ctly arbitrary states using a universal quantum cloning machine. They have analyzed their result using the Hilbert Schmidt norm, although a better mea sure of fidelity is the Bures metric. In this paper, we repeat the Buzek an d Hillery result using the Bures metric and show that we can still obtain t he same result with an improved measure. However, unlike the Hilbert-Schmid t norm, this computation may be extended to the case of continuous variable , infinite-dimensional spaces, or even Hilbert spaces of larger dimensions. For completeness, a similar analysis using the trace norm is also performe d.