QUROPE Quantum Information Processing and Communication in Europe

A procedure is discussed for creating coherent superpositions of motional states of ion strings. The motional states are across the structural transition linear-zigzag, and their coherent superposition is achieved by means of spin-dependent forces, such that a coherent superposition of the electronic states of one ion evolves into an entangled state between the chain's internal and external degrees of freedom. It is shown that the creation of such an entangled state can be revealed by performing Ramsey interferometry with one ion of the chain.

The talk was delivered by Prof. J. Taylor (UMD/NIST) on the topic: Exploring new frontiers of quantum science with hybrid systems.

We analyze a quantum reservoir engineering method, originally introduced by [Sarlette et al. in Phys. Rev. Lett. 107, 010402 (2011) -- arXiv 1011.5057], for the stabilization of non-classical field states in high quality cavities. We generalize the method to the protection of mesoscopic entangled field states shared by two non-degenerate field modes. The reservoir is made up of a stream of atoms undergoing successive composite interactions with the cavity, each combining resonant with non-resonant parts.

Following QIPC2009 in Rome and QIPC2011 in Zurich we have the pleasure to announce another edition of the QUANTUM INFORMATION PROCESSING AND COMMUNICATION CONFERENCE – QIPC2013.

The reports are available for public download at the WP2 deliverables page. They contain a detailed description of the features that are integrated in the qurope.eu web site, that allow a classification and analysis of the database material that is relevant to QIPC.

The round table is organized during the ICAP 2012 conference, and is one of the highlights of several special events. This public event is sponsored by the 'Quantum Envoy' program of the Coordination Action QUIE2T.

Current attempts to probe general relativistic effects in quantum mechanics focus on precision measurements of phase shifts in matterwave interferometry. Yet, phase shifts can always be explained as arising because of an AharonovBohm effect, where a particle in a flat spacetime is subject to an effective potential. Here we propose a quantum effect that cannot be explained without the general relativistic notion of proper time.

Quantum states and measurements exhibit wave-like - continuous, or particle-like - discrete, character. Hybrid discrete-continuous quantum optical systems are key to investigating fundamental quantum phenomena such as the violation of local realism by Einstein-Podolsky-Rosen states, measuring non-classical correlations of radiation fields and superpositions of macroscopic states, and form essential resources for quantum-enhanced applications and high- efficient optical telecommunications.

We show that the process of three-wave mixing in a non-linear crystal (such as employed in down conversion processes) can be used for versatile weak measurements. That is the crystal field interaction Hamiltonian enables weak measurements of pairs of complementary variables. To obtain the weak value of variable $A$ one has to perform weak measurements twice. This seems to be drawback, but as a compensation we get for free the weak value of a complementary variable $B$.

Studying mechanical resonators via radiation pressure offers a rich avenue for the exploration of quantum mechanical behavior in a macroscopic regime. However, quantum state preparation and especially quantum state reconstruction of mechanical oscillators remains a significant challenge. Here we propose a scheme to realize quantum state tomography, squeezing, and state purification of a mechanical resonator using short optical pulses.