It is shown that a simplified version of the error correction code recently suggested by Shor [Phys. Rev. A 52, R2493 (1995)] exhibits manifestation of the quantum Zeno effect. Thus, under certain conditions, protection of an unknown quantum state is achieved. Error prevention procedures based on four-particle and two-particle encoding are proposed and it is argued that they have feasible practical implementations.

• Received 29 March 1996

DOI:https://doi.org/10.1103/PhysRevA.54.R1745