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MALICIA at glance

MALICIA – Light-Matter interfaces in absence of cavities

Targeted breakthrough and long-term vision

A fundamental research and technological challenge to be addressed in the very near future concerns the integration of different platforms for the implementation of Quantum Information Technologies (QIFT). Indeed different physical systems have been considered: ultracold atoms, room temperature gases, trapped ions, superconducting Josephson Junctions, quantum dots, … Many experiments have demonstrated fundamental steps towards the realization of e.g. a quantum computer such as single q-bit operations, quantum phase gates, quantum memories etc. However different systems have different advantages and no single one seems, at the present stage, to be the perfect candidate. The most promising strategy, therefore, appears to be the integration of different platforms.

During the past decade the interaction of light with multi-atom ensembles has attracted a lot of attention as a basic building block for quantum information processing and quantum state engineering. The field started with the realization that optically thick free space ensembles can be efficiently interfaced with quantum optical fields. By now, atomic ensemble / light interfaces have become a powerful alternative to cavity-enhanced interaction of light with single atoms, while removing the demand for high-finesse optical cavities associated with the latter.

We will address various mechanisms used for the quantum interface, including quantum non-demolition swap and light-atoms beam-splitter interactions, quantum measurement and feedback, Rydberg interaction and electromagnetically induced transparency. Indeed all of these mechanisms share two well-identified quantum measurements: homodyne detection and photon counting. The new expertise emerging from our project will provide a platform for progress in Information and Communication Technology (ICT).

Interfaces of light with matter based on atomic ensembles in free space made significant progress in the last years, and many proof-of-principle experiments successfully demonstrated elementary functions, such as e.g. storage and release of light pulses, entanglement of stored excitations at a distance, or light-to-matter teleportation, coherent control of the Rydberg blockade. It is now a timely task to design the next generation of light-matter interfaces, exhibiting both new functionalities and improved performance.

The objective of the present program is to explore three well defined new platforms: high temperature micro-cells with Rydberg blockaded samples, micro-fabricated room temperature cells, nanostructured ultracold gases coupled to nanostructured optical materials. These three approaches share common methodologies but are based on very different experimental platforms all at the edge of what is technically feasible and with a great potential for development.

Micro-cells with Rydberg blockaded samples promises a number of advantages over semiconductor quantum dots as single photon sources such as scalability, efficiency and compatibility with quantum memories. One of the aims of this project will be demonstrating the blockade effect in thermal cells, to use a four-wave mixing configuration to demonstrate the first single photon source based on the blockade effect and to characterize and optimize this source as for its fidelity.

Micro-fabricated room temperature cells offers a very robust and practical approach. Several advances including quantum memory for coherent states and teleportation from light onto a memory have been demonstrated with such systems. One of our aims is to attack problems of non-QND character, and to investigate the interplay between collective and individual dynamics in the atoms and to investigate new approaches harnessing the coupling of atomic systems to the environment, which drives the system into the desired state.

Nanostructured ultracold gases offer the possibility to realize massively entangled systems. Harnessing this quantum resource is one of the aims of this project. Coupling to nanostructured materials we intend to realize a versatile experimental set-up where atoms can be laser cooled to quantum degeneracy and brought at submicron distances from nanostructured surfaces. This will open up a wealth of new possibilities by permitting the true integration of optical circuits on an AtomChip connecting the world of ultra-cold atoms to that of photonic devices.

The three experimental approaches pursued by MALICIA complement each other not only in the sense that they can be integrated, but also that they are and remain distinct, in such a way that our project can offer a solution even if one of them should turn out not to work as expected. If every approach were dependent on every other, failure of one would imply failure of the whole project. In MALICIA this will not be the case since we are pursuing complementary and partially independent approaches.

The absence of high finesse optical cavities in our setups allows for the use of much larger frequency bandwidths offering the possibility for faster operation. Overall the different approaches we pursue share an effort towards reducing experimental complexity, improving system performances, allowing faster and more reliable operation really challenging current thinking exploiting new emerging technologies.