QUROPE Quantum Information Processing and Communication in Europe

We discuss in details a modified variational matrix-product-state algorithm for periodic boundary conditions, based on a recent work by P. Pippan, S.R. White and H.G. Everts, Phys. Rev. B 81, 081103(R) (2010), which enables one to study large systems on a ring (composed of N ~ 10^2 sites). In particular, we introduce a couple of improvements that allow to enhance the algorithm in terms of stability and reliability. We employ such method to compute the stiffness of one-dimensional strongly correlated quantum lattice systems.

Optical detected electron spin resonance is a powerful tool to study the coherence properties of electron spin coherence properties. In particular for an electron trapped in a single self-assembled quantum dot (QD) the electron spin coherence is strongly influenced by the nuclear spin dynamics; The electron interacts via hyperfine interaction with ~300000 nuclear spins whose random fluctuating distripution usually lead to significant reduction of electron spin coherence.

Spins confined in semiconductor quantum dots offer new possibilities for realizing quantum optical systems with unique properties. Conversely, optical measurement techniques provide a powerful tool for studying mesoscopic condensed-matter systems.

Accurately controlling a quantum system is a fundamental requirement in quantum information processing and the coherent manipulation of molecular systems. The ultimate goal in quantum control is to prepare a desired state with the highest fidelity allowed by the available resources and the experimental constraints. Here we experimentally implement two optimal high-fidelity control protocols using a two-level quantum system comprising Bose–Einstein condensates in optical lattices.