Introducing Quantum Key Distribution

Georgi Bebrov

Quantum key distribution (QKD) systems require optimal performance of both quantum and classical channels - utilizing as few as possible qubits and bits for establishing as many as possible key bits. Here we report a way to determine if a quantum key distribution model (or protocol) operates in an optimal behavior. This is accomplished by introducing a quantity, called optimality, which is the maximum over the total efficiency of a QKD under any circumstances (any values of QKD parameters). The optimality definition is given for the asymptotic operation of a QKD system - when infinitely many quantum systems are transferred/used in a quantum key distribution protocol or a quantum key distribution system is used infinitely many times. A way to attain the optimality is considered\textemdash implementation of a completely efficient QKD system (a combination of capacity-reaching quantum channel and a completely compressed classical channel) is presented. Optimal versions of BB84-QKD and twin-field QKD are introduced.

G. Ribordy, Nicolas Gisin, Hugo Zbinden

Roszelinda Khalid, Zuriati Ahmad Zukarnain

This research is introducing an enhanced tight finite key scheme for quantum key distribution (QKD) protocol to authenticate multi-party system in cloud infrastructure. The main attraction is to provide a secure channel between a cloud client to establish a connection among them by applying the theories from Von Neumann and Shannon entropies and also Shor's algorithm. By generalizing these theories we will produce enhanced tight finite key scheme for quantum key distribution (QKD) protocol to authenticate multi-party system in cloud infrastructure. Hence we are using quantum channel and also quantum key distribution (QKD) together with BB84 protocol replacing common channel to distribute the key. We are proposing an authentication of multi-party Quantum Key Distribution (MQKD) protocol using an enhanced tight finite key scheme because it will involve a number of parties in cloud infrastructure. Significant of this research is to reduce the possibility of losing a private key by producing a high efficient key rate and attack resilient.

Ch. Seshu

Vinod N. Rao, R. Srikanth

Counterfactual quantum key distribution (QKD) enables two parties to share a secret key using an interaction-free measurement. Here, we point out that the efficiency of counterfactual QKD protocols can be enhanced by including noncounterfactual bits. This inclusion potentially gives rise to the possibility of noiseless attacks, in which Eve can gain knowledge of the key bits without introducing any errors in the quantum channel. We show how this problem can be resolved in a simple way that naturally leads to the idea of ``counterfactual security,'' whereby the noncounterfactual key bits are indicated to be secure by counterfactual detections. This method of enhancing the key rate is shown to be applicable to various existing quantum counterfactual key distribution protocols, increasing their efficiency without weakening their security.