Quantum Information Processing Early Stage Training Network

Quantum information processing (QIP) algorithms and the basic theory for quantum computers are already well established. The important next step which will make a huge impact on the whole field of information technology is to develop quantum information processing devices which contain small quantum processors. A single physical system will probably not be able to fulfil all requirements for its realization. Hybrid architectures which combine the best properties of several physical systems are thus very likely to be among the first to realize such quantum information processing devices. Scientific and industrial research on such hybrid technologies as well as their industrial development require scientists with very broad background knowledge in different theoretical and experimental areas of physics and material sciences who are able to work successfully in an interdisciplinary team. Advanced theoretical concepts and quantum algorithms need to be adapted to concrete physical realizations which might contain components developed in different areas of physics and material science. The unique combination of research training opportunities in an interdisciplinary environment of highest level research will train students in all important areas of quantum information processing. Their training will end in 2009/2010 when according to current projections (ARDA roadmap, ERA-Pilot QIST) the transfer of basic QIP knowledge to the industry is likely to be of increasing importance. There will be a high demand for researchers with the expertise provided in this research training project in the academic as well as in the industrial sectors.

Investigators:

D. Jaksch

Collaborators:

D. Jaksch (Co-ordinator) , I.A. Walmsley and G.A.D. Briggs

EU Early stage training network; MEST-CT-2005-020505

Start date:

2006-04-22

End date:

2010-04-21

Related Publications

M. Rosenkranz, A. Klein and D. Jaksch, Simulating and detecting artificial magnetic fields in trapped atoms, Phys. Rev. A 81, 013607 (2010).
Abstract

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Simulating and detecting artificial magnetic fields in trapped atoms

A Bose-Einstein condensate exhibiting a nontrivial phase induces an artificial magnetic field in immersed impurity atoms trapped in a stationary, ring-shaped optical lattice. We present an effective Hamiltonian for the impurities for two condensate setups: the condensate in a rotating ring and in an excited rotational state in a stationary ring. We use Bogoliubov theory to derive analytical formulas for the induced artificial magnetic field and the hopping amplitude in the limit of low condensate temperature where the impurity dynamics is coherent. As methods for observing the artificial magnetic field we discuss time-of-flight imaging and mass current measurements. Moreover, we compare the analytical results of the effective model to numerical results of a corresponding two-species Bose-Hubbard model. We also study numerically the clustering properties of the impurities and the quantum chaotic behavior of the two-species Bose-Hubbard model.

We investigate the effect of a rotating Bose-Einstein condensate on a system of immersed impurity atoms trapped by an optical lattice. We analytically show that for a one-dimensional, ring-shaped setup the coupling of the impurities to the Bogoliubov phonons of the condensate leads to a non-trivial phase in the impurity hopping. The presence of this phase can be tested by observing a drift in the transport properties of the impurities. These results are quantitatively confirmed by a numerically exact simulation of a two-mode Bose-Hubbard model. We also give analytical expressions for the occurring phase terms for a two-dimensional setup. The phase realises an artificial magnetic field and can for instance be used for the simulation of the quantum Hall effect using atoms in an optical lattice.

created: 15-08-2008, last modified: 19-01-2009

A. Klein, M. Bruderer, S.R. Clark and D. Jaksch, Dynamics, dephasing and clustering of impurity atoms in Bose-Einstein condensates, New J. Phys. 9, 411 (2007).
Abstract

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Dynamics, dephasing and clustering of impurity atoms in Bose-Einstein condensates

We investigate the influence of a Bose-Einstein condensate (BEC) on the properties of immersed impurity atoms, which are trapped in an optical lattice. Assuming a weak coupling of the impurity atoms to the BEC, we derive a quantum master equation (QME) for the lattice system. In the special case of fixed impurities with two internal states the atoms represent a quantum register and the QME reproduces the exact evolution of the qubits. We characterize the qubit dephasing which is caused by the interspecies coupling and show that the effect of sub- and super-decoherence is observable for realistic experimental parameters. Furthermore, the BEC phonons mediate an attractive interaction between the impurities, which has an important impact on their spatial distribution. If the lattice atoms are allowed to move, there occurs a sharp transition with the impurities aggregating in a macroscopic cluster at experimentally achievable temperatures. We also investigate the impact of the BEC on the transport properties of the impurity atoms and show that a crossover from coherent to diffusive behaviour occurs with increasing interaction strength.