QUIE2T Quantum Information Entanglement-Enabled Technologies

 We study the single particle dynamics of a mobile non-Abelian anyon hopping around many pinned anyons on a surface. The dynamics is modelled by a discrete time quantum walk and the spatial degree of freedom of the mobile anyon becomes entangled with the fusion degrees of freedom of the collective system. Each quantum trajectory makes a closed braid on the world lines of the particles establishing a direct connection between statistical dynamics and quantum link invariants.

The European Commission has sent us the official approval to our request to add the Johannes Gutenberg Universität Mainz (JOGU Mainz) among the AQUTE partners, following the move of Professor Ferdinand Schimdt-Kaler from Ulm to Mainz.

Scientists at the Max Planck Institute of Quantum Optics succeed in recording single-atom resolved images of a highly correlated quantum gas.

Ultracold atoms in optical lattices have evolved in the last years into an interdisciplinary tool for many-body solid state and quantum physics. But so far only limited possibilities were available to manipulate and to image the quantum gas on a microscopic scale. For the first time a team around Stefan Kuhr and Immanuel Bloch at MPQ has now succeeded in observing – atom by atom, lattice site by lattice site – such a strongly correlated system (Nature, 18 August 2010, DOI 10.1038/nature09378). The physicists saw that under certain conditions the atoms in the optical lattice arrange in a very regular distribution, with a fixed number of atom per lattice site. This is an important precondition for using these systems as quantum registers with individually addressable quantum bits in future quantum computers.

Physicists in Germany have used fluorescence imaging to identify individual particles in an optical lattice for the first time. The breakthrough could allow researchers to create more advanced simulations of quantum phenomena and it might help in the quest for practical quantum computing.

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 We present a fault-tolerant semi-global control strategy for universal quantum computers. We show that N-dimensional array of qubits where only (N-1)-dimensional addressing resolution is available is compatible with fault-tolerant universal quantum computation. What is more, we show that measurements and individual control of qubits are required only at the boundaries of the fault-tolerant computer, i.e. holographic fault-tolerant quantum computation.

The Commission ICT Work-Programme 2011-2012 feature an interesting Objective under FET-Open, namely "Objective ICT-2011.9.4: International cooperation on FET research". This consist in a funding scheme that provides additional funding to existing grant for on-going FET IPs and STREPs ending at least 18 months after the submission date of the proposal (click on the tab below to access the full Objective text as published in the WP).

We analyze in detail the so-called pushing gate for trapped ions, introducing a time-dependent harmonic approximation for the external motion. We show how to extract the average fidelity for the gate from the resulting semiclassical simulations. We characterize and quantify precisely all types of errors coming from the quantum dynamics and reveal that slight nonlinearities in the ion-pushing force can have a dramatic effect on the adiabaticity of gate operation.

We introduce a new approach to quantify the robustness of optimal control of closed quantum systems. Our theory allows to assess the degree of distortion that can be applied to a set of known optimal control parameters, which are solutions of an optimal control problem. The formalism is applied to an exactly solvable model and to the Landau-Zener model, whose optimal control problem is solvable only numerically. The presented method is of importance for any application where a high degree of controllability of the quantum system dynamics is required.