We study measurements on various subsystems of the output of a universal $\overrightarrow{1}2$ cloning machine, and establish a correspondence between these measurements at the output and effective measurements on the original input. We show that one can implement sharp effective measurement elements by measuring only two out of the three output systems. Additionally, certain complete sets of sharp measurements on the input can be realized by measurements on the two clones. Furthermore, we introduce a scheme that allows us to restore the original input in one of the output bits, by using measurements and classical communication—a protocol that resembles teleportation.

• Received 16 November 2000

DOI:https://doi.org/10.1103/PhysRevA.63.042308