I am currently interested to develop several information and communication protocols (including cryptographic protocols) with device-independent (DI) security proof by using quantum resources. Then compare the efficiency of these protocols with their classical counterpart. I would also intend to study the characteristics of the multipartite correlations and develop new tools to detect multipartite entanglement.

The security of classical key distribution protocols are mostly rely on assumed limitations on an eavesdropper's computational power such as factorization problem is hard to solve within a limited time or the availability of resources e.g., noisy channels. Therefore, they are not secure in true sense. To defeat this Bennett and Brassard introduced a quantum key distribution (QKD) protocol in 1984, presently this pioneer work known as BB84 protocol. The security of BB84 protocol is based primarily on the existence of non-orthogonal state vectors in the Hilbert space. In 1991, Ekert proposed another QKD protocol the security of which is based on a different property of Hilbert space: the monogamy of entanglement of a pure entangled state. Two systems which are strongly entangled (correlated) can at most be weakly entangled with a third system.

The laws of quantum theory permit an unconditional security proof of QKD and other quantum protocols. However, the devices used in the protocols might have concealed flaws introduced by an untrustworthy manufacturer or saboteur, which can be difficult to identify, since (a) it is easy to design quantum devices that appear to be following a secure protocol but are actually completely insecure, and (b) there is no general technique for identifying all possible security loopholes of devices used in any standard quantum protocol. This has led to much interest in DI quantum protocols, which aim to guarantee security only on testable features of the devices, for example, the statistics of their behaviour and no specification of internal functionality of the devices is required. From a theoretical perspective, some DI quantum protocols provided a satisfactory security proof. Nonetheless, they require a separate and isolated pair of devices for each entangled pair to ensure full device-independent security. This evidently makes such protocols impossible to implement in practice. Therefore, finding an efficient secure DI quantum scheme using two (or few) devices has remained an open theoretical challenge. In this regard there is a hope with the DI protocols based on non-inequality paradoxes where devices can be reused. Our recent result of DI-QKD scheme based on Hardy’s paradox shows that at least in ideal case devices can be re-sued not only in a single protocol but the same devices can also be used in any future protocol of similar type.

Genuine multipartite entangled state plays key role in most of the DI quantum protocols including the QKD. Many features of multipartite correlations are not clearly understood still now specially, the structure of the genuine multipartite entangled states. In this context we have proposed several tests for detecting genuine multipartite entanglement for some restricted class of states based on different non-inequality paradoxes like Hardy's argument, Cabello's argument etc. Therefore, it is worthy to study and develop genuine multipartite entanglement test for a more general class of states based on different non-inequality paradoxes.

In short, my main goal is to study extensively the device-independent security proof of quantum protocols based on different non-inequality paradoxes such as Hardy paradox, Cabello paradox, GHZ paradox etc., and design efficient DI protocols which guarantee unconditional security and possible to implement in realistic condition. In this processes, I also like to study the allied problems of detecting genuine multiparty entanglement. Therefore, I would very much love to continue this research at the Department of Informatics, University of Bergen, Bergen, Norway if I have the chance. Studying above problem may help in solving or suggesting some new problems in the area of quantum information theory in general and secure quantum communication in particular.