QUANTUM COMMUNICATION AND CRYPTOGRAPHY

Abstract

Computeriscience i isifundamentally ilinked i to ithe iphysical iworld. The imachines iwe iuse ito iaccess ithe iInternet, ithe iJava iprograms iwritten iby ia istudent iin ian iintroductory icomputer iscience iclass, iand i indeed ieverything iwe igenerally irefer i to ias ia i“computer”is i based i on i a iset i of i physical i assumptions. iUnfortunately, i the i underlying i physical i assumptionsion iwhich inearly iall imodern icomputers irely iare ioutdated. iThe itwentieth icentury isawithe irise iofiquantumimechanics, irevealingistrangeiphenomenaiincludingisuperposition iandientanglement, iwhileiweiareistillistuckiwithicomputersibasedioniclassicaliphysics. iTheinewiand iincredibly irich ifield iof iquantum icomputation iand iinformation iseeks ito iharness ithe ipower iof iquantumimechanicsiiniorderito idevelop isignificantly imore ipowerful icomputational i techniques i . The iclassical ipicture iof ithe iworld iis iintuitive. iWe ithink iof ielectric icurrent ias ithe imotion iof ielectronsiacrossiaivoltage, iandiofielectronsiasidiscrete iparticles. iTheyicannotibeiinimoreithanione istate isimultaneously, iand ithey ihave ia idefinite ilocation, imomentum, ienergy iand itime. iQuantum imechanics i is imore ibizarre. iQuantum icomputers iopen iup ia islew iof inew icryptographic ipossibilities, iincludingikeyidistribution, iconfidentiality, iintegrity, iandinon-repudiation. iQuantum icryptographic itechniques idiffer isignificantly ifrom iconventional icryptography idue ito ithe idestructive iand iprobabilistic icharacter iof iquantum imeasurements, ias iwell ias ithe ino-cloning itheorem, iwhich iforbids ithe iduplication iof iquantum istates. iAlthough ia ivast inumber iof ithese imethodsihave ibeen ipresented, ithere ihasibeen ilittle icomparative iresearch. iIn iorder ito iprovide ian ioverviewiofitheipresentistateiofitheisubject, iweiconductiaistudyiofiexistingiprotocolsiwithiaifocus ion ipractical iapplications.. iWe ialso ishow ihow ito imake ia iquantum icryptography ialgorithm ithat iprovides iconfidentiality, iintegrity, iand inon-repudiation. iAdditionally, iwe igeneralise iour iimplementation imethod ito igive ia itemplate iforiconverting ialgorithmsifromia iresearch iarticle ito ia iquantumiprogrammingienvironment. i