Quantum Computation and Information Seminar 

28/07/2008, 10:00 — 11:00 — Conference Room, Instituto de Telecomunicações, IST
Konrad Banaszek, U Nicolaus Copernicus, Torun

Quantum Communication in the Presence of Noise - Part 1

Fluctuations inherent to quantum physics are commonly recognized to impose ultimate bounds on the performance of communication systems. At the same time, full exploitation of quantum theory opens up routes to improve communication through the use of non-classical phenomena such as entanglement and offers new groundbreaking applications, for example quantum cryptography. Implementation of these schemes has to be made robust against noise appearing in practical communication systems. In this talk, we will discuss two kinds of noise typical to fiber optic links: depolarization and losses. We will show that the use of entanglement can be used to increase the classical capacity of depolarizing channels, which will lead us to the notion of decoherence-free subspaces and subsystems. We will also discuss how superposition states can be protected from losses in quantum optical communication using concepts derived from the theory of quantum error correction.