Quantum Key Distribution with Qubits Encoded in Qutrit
  We present a novel one-way quantum key distribution protocol based on 3-dimensional quantum state, a qutrit, that encodes two qubits in its 2-dimensional subspaces. The qubits hold the classical bit information that has to be shared between the legitimate users. Alice sends such a qutrit to Bob where he decodes one of the qubit and measures it along the random Pauli basis. This scheme has higher secure key rate at longer transmission distance than the standard BB84 protocol. 
R.Kumar, R.Demkowicz-Dobrzanski and K.Banaszek
quant-ph