QUROPE Quantum Information Processing and Communication in Europe

We measure atom number statistics after splitting a gas of ultracold 87Rb atoms in a purely magnetic double-well potential created on an atom chip. Well below the critical temperature for Bose-Einstein condensation Tc, we observe reduced fluctuations down to -4.9  dB below the atom shot noise level.

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T. Caneva (P1.b Universität Ulm), poster, Optimal control at the quantum speed limit.

We propose and analyze a scheme for sympathetic cooling of the translational motion of polar molecules in an optical lattice, interacting one by one with laser-cooled ions in a radio-frequency trap. The energy gap between the excitation spectra of the particles in their respective trapping potentials is bridged by means of a parametric resonance, provided by the additional modulation of the RF field. We analyze two scenarios: simultaneous laser cooling and energy exchange between the ion and the molecule, and a scheme when these two processes take place separately.

Trapped laser-cooled atoms and ions are quantum systems which can be experimentally controlled with an as yet unmatched degree of precision. Due to the control of the motion and the internal degrees of freedom, these quantum systems can be adequately described by a well-known Hamiltonian. In this colloquium, powerful numerical tools for the optimization of the external control of the motional and internal states of trapped neutral atoms, explicitly applied to the case of trapped laser-cooled ions in a segmented ion-trap are presented.

Spin chains have long been considered as candidates for quantum channels to facilitate quantum communication. We consider the transfer of a single excitation along a spin-1/2 chain governed by Heisenberg-type interactions. We build on the work of Balachandran and Gong [V. Balachandran and J. Gong, Phys. Rev. A 77, 012303 (2008)] and show that by applying optimal control to an external parabolic magnetic field, one can drastically increase the propagation rate by two orders of magnitude.

• ion trapping
• atom trapping
• entangled photons
• atom-photon interfaces
• single-photon sources
• cavity QED
• laser cooling

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.

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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