IIIT Hyderabad Publications
Problems in Quantum Cryptography and Communications
Author: Maharshi Ray
Report no: IIIT/TH/2016/17
Advisor:Indranil Chakrabarty,Harjinder Singh
The field of quantum information and computing has gained a lot of attention in the past couple of decades. It is an inter-disciplinary field comprising of mathematics, physics and computer science. Researchers have been able to exploit the quantum properties like superposition and entanglement to improve the efficiency of classical algorithms and communication and cryptographic protocols. In this thesis, we address a few problems in quantum cryptography and communications. We introduce the basic mathematical structures and postulates of quantum theory in the first chapter. We also describe the basic quantum information tools which are essential of this thesis. The field of quantum cryptography is introduced here as well.In the second chapter, we address a problem in quantum secret sharing schemes. We give a protocol for sequential quantum secret sharing where the dealer does not have access to all the secrets at the beginning of the protocol. We also show that the resource requirement for our protocol is optimal. We analyze our protocol in case of a noisy quantum channel. We use weak measurements to demonstrate that the efficiency of the protocol in such noisy environments can be enhanced. In the third chapter. we address a problem in a new emerging sub field of quantum cryptography, namely, device independent cryptography. We discuss the issues of the usual quantum cryptographic schemes and show how device independent cryptography addresses some of those issues. In particular, we deal with the case when Alice and Bob has been provided with untrusted devices and Eve can control Bob’s detectors using tailored bright pulses. We analyze the security of such attacks in a semi-device independent scenario and give the sufficient conditions for unconditional security. In the final chapter, we introduce an useful information processing task, namely broadcasting of correlations. It essentially deals with the procedures of creating a larger number of less correlated systems from a highly correlated system. Then we move on to broadcasting of general correlations (possibly even stronger than quantum correlations). We introduce the the mathematical framework and define linear transformation rules. We study the correlation properties of the resulting resources in terms of the initial correlations and transformation parameter.
Full thesis: pdf
Centre for Computational Natural Sciences and Bioinformatics
Copyright © 2009 - IIIT Hyderabad. All Rights Reserved.