2000/03/07 by Julia Kempe, Christoph Simon, Gregor Weihs
Computer Science · Physics and Astronomy · #Quantum Computing Algorithms and Architecture #Quantum Information and Cryptography #Quantum Mechanics and Applications #quant-ph
paper · pdf · doi:10.1103/physreva.62.032302
published as Phys. Rev. A 62, 032302 (2000) · 10 pages
arxiv created 2000/03/07 · openalex publication_date 2000/08/08 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
We show that optimal universal cloning of the polarization state of photons can be achieved via stimulated emission in three-level systems, both of the \ensuremathΛ and the V type. We establish the equivalence of our systems with coupled harmonic oscillators, which permits us to analyze the structure of the cloning transformations realized. These transformations are shown to be equivalent to the optimal cloning transformations for qubits discovered by Bu\ifmmode \checkz\else \vz\fiek and Hillery and Gisin and Massar. The down-conversion cloner discovered previously by some of the authors is obtained as a limiting case. We demonstrate an interesting equivalence between systems of \ensuremathΛ atoms and systems of pairwise entangled V atoms. Finally we discuss the physical differences between our photon cloners and the qubit cloners considered previously and prove that the bounds on the fidelity of the clones derived for qubits also apply in our situation.