Error Prevention Scheme with Four Particles
  It is shown that a simplified version of the error correction code recently suggested by Shor 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. 
Lev Vaidman, Lior Goldenberg and Stephen Wiesner