From the foundations of quantum theory to quantum technology - An Introduction

Nowadays, the new technological prospects of processing quantum information in quantum cryptography, quantum computation and quantum communication attract not only physicists but also researchers from other scientific communities, mainly computer scientists, discrete mathematicians and electrical engineers. Current developments demonstrate that characteristic quantum phenomena which appear to be surprising from the point of view of classical physics may enable one to perform tasks of practical interest better than by any other known method. In quantum cryptography, the nocloning property of quantum states or the phenomenon of entanglement helps in the exchange of secret keys between various parties, thus ensuring the security of one-time-pad cryptosystems. Quantum parallelism, which relies on quantum interference and which typically also involves entanglement, may be exploited for accelerating computations. Quantum algorithms are even capable of factorizing numbers more efficiently than any known classical method is, thus challenging the security of public-key cryptosystems such as the RSA system. Classical information and quantum information based on entangled quantum systems can be used for quantum communication purposes such as teleporting quantum states