Feng, Yuan; Zhang, Shengyu; Sun, Xiaoming; Ying, Mingsheng Universal and original-preserving quantum copying is impossible. (English) Zbl 0994.81023 Phys. Lett., A 297, No. 1-2, 1-3 (2002). Summary: We show that an arbitrary quantum state cannot be universally \(1\rightarrow 2\) copied keeping the original copy unchanged. Indeed, the density operator of the additional copy after the copying transformation is nothing but the scale product of the identity matrix with factor 1/2, which involves no information of the original state. Cited in 1 Document MSC: 81P68 Quantum computation Keywords:density operator; quantum state PDFBibTeX XMLCite \textit{Y. Feng} et al., Phys. Lett., A 297, No. 1--2, 1--3 (2002; Zbl 0994.81023) Full Text: DOI References: [1] Wootters, W. K.; Zurek, W. H., Nature (London), 299, 802 (1982) [2] Dieks, D., Phys. Lett. A, 92, 271 (1982) [3] Buzek, V.; Hillery, M., Phys. Rev. A, 54, 1844 (1996) [4] Bruß, D.; DiVincenzo, D. P.; Ekert, A.; Fuchs, C. A.; Macchiavello, C.; Smolin, J. A., Phys. Rev. A, 57, 2368 (1998) [5] Bruß, D.; Ekert, A.; Macchiavello, C., Phys. Rev. Lett., 81, 2598 (1998) [6] Gisin, N.; Massar, S., Phys. Rev. Lett., 79, 2153 (1997) [7] Werner, R. F., Phys. Rev. A, 58, 1827 (1998) This reference list is based on information provided by the publisher or from digital mathematics libraries. Its items are heuristically matched to zbMATH identifiers and may contain data conversion errors. In some cases that data have been complemented/enhanced by data from zbMATH Open. This attempts to reflect the references listed in the original paper as accurately as possible without claiming completeness or a perfect matching.