Quantum cryptography with 3-state systems
  We consider quantum cryptographic schemes where the carriers of information are 3-state particles. One protocol uses four mutually unbiased bases and appears to provide better security than obtainable with 2-state carriers. Another possible method allows quantum states to belong to more than one basis. The security is not better, but many curious features arise. 
Helle Bechmann-Pasquinucci and Asher Peres