I investigate the security, efficiency and feasibility of quantum crypto-protocols namely quantum signatures, quantum oblivious transfer and other crypo-systems.  Along with collaborators, I have developed a significant quantum signature crypto-system that can guarantee security against eavesdroppers who exploit imperfections in detectors. This uses the concept of measurement-device-independence and the experimental implementation of the signature scheme was accomplished in collaboration with experimental crypto-groups at Toshiba Research Europe Limited (TREL) and with Prof. J.W. Pan's group at University of Science and Technology of China.

Quantum state elimination (QSE) measurements provides us the information about the states that a quantum system doesn't have. For instance, if we perform a projective measurement in some basis, then corresponding to the outcome obtained we can eliminate any state which is orthogonal to the basis state. In this joint work with collaborators, we have derived unambiguous measurements for eliminating one and two out of the four possible two-qubit states, and established the experimental implementation of this realisation. Along with my collabortors at Heriot-Watt University, Palacky University and University of Edinburgh, we have implemented an Oblivious Transfer crypto-protocol using QSE.

I have used techniques from a field in theoretical computer science known as formal methods, to model and analyse realistic quantum information processing (QIP) systems. This line of research referred to as quantum process calculus, that helps to describe and analyse the behaviour of concurrent and communicating systems that combine quantum and classical elements. By using the theory of behavioural equivalence in a quantum process calculus called Communicating Quantum Processes (CQP), I was able to describe and provide a systematic verification of a quantum error correction system, higher dimentional quantum protocols such as  qudit teleportation and superdense coding, and linear optical quantum computing.

With my collaborators at the University of Bristol and Heriot-Watt University, we have implemented a classical crypto-system on a quantum network. This is an unconditionally secure signature scheme and I lead the theoretical aspects of this research. The scheme involves in using digital signatures in an eight user quantum work that runs five different anonymity protocols. Additonally, in this research, we demonstrate protocols beyond quantum key distribution in quantum networks.