QKD: Recovering Unused Quantum Bits

Practical quantum key distribution gain is usually less than the theoretical limit, this is due to the imperfection of physical devices, quantum channels, and the lost qubits due to test carried out for for the identification of the presence of an eavesdropper and the consequence reduction of obtained knowledge. In this paper a technique is presented to recover some of the unused qubits which result in an increase in the gain of the QKD protocols, in this research it was found that for the BB84 the recovered qubits can be as much as 11% of the initial key bits. This technique is based on discovering the relationship between the initial key bits and the original random bits which will aid in the recovery process of the unused qubits ( unused qubits are the bits which are assumed to be lost at the start of the process due to the random process and for BB84 it is assumed to be around 50% of the generated key bits).