Eur. Phys. J. D 51, 381-385 (2009)
https://doi.org/10.1140/epjd/e2008-00227-7

Quantum cloning machine of a state in a belt of Bloch sphere

¹ Department of Physics, Tsinghua University, Beijing, 100084, P.R. China
² Department of Mathematical Sciences, Tsinghua University, Beijing, 100084, P.R. China
³ Tsinghua National Laboratory for Information Science and Technology, Beijing, 100084, P.R. China

Corresponding author: ^a xbwang@mail.tsinghua.edu.cn

Received: 26 July 2008
Revised: 28 October 2008
Published online: 5 December 2008

Abstract

We analyze the problem of approximate quantum cloning when the quantum state is between two latitudes on the Bloch's sphere. We present an analytical formula for the optimized 1-to-2 cloning. The formula unifies the universal quantum cloning (UQCM) and the phase covariant quantum cloning.