MOLOPTLAT · Molecule formation and quantum correlations in optical lattices

Molecule formation and quantum correlations in optical lattices

Project objectives We investigated the use of cold molecules for quantum information processing and communication (QIPC), as well as the application of protocols and schemes from QIPC to molecular physics and, in particular, to molecular spectroscopy. Our work has built on the steady progress during the last 10 years on the production and manipulation of cold atomic and molecular gases with several techniques, most notably in optical lattices, which has opened the door for novel applications of molecules to quantum information technologies. Project work In this context, the first problem we addressed was the analytical description of a system composed of two atoms trapped in neighbouring sites of an optical lattice, and interacting via long-range van der Waals potentials, with the aim of determining the conditions in which quantum logic gates and entanglement could be realised. This work, developed during the first few months of the project, lead to the conclusion that van der Waals interactions are too weak at typical optical-lattice inter-site distances, and that a stronger interaction would be required for QIPC purposes. Noting the rapid progress in the production of cold molecular ions, with several key experiments published during 2010, and taking into account the notable expertise of the host group and scientific coordinator in the study of quantum information processes with atomic ions, we decided to analyse the prospects for achieving such processes with molecular species. Project results We have developed a flexible, fast and robust spectroscopic scheme suitable for studying electronic, vibrational, rotational, or hyperfine transitions in cold molecular ions, setting a starting point for new hybrid atomic-molecular quantum computation schemes. In addition, we have identified the molecular oxygen ion as a candidate to realise a molecular qubit, with a well-defined two-state system and inherent protection against magnetic-field fluctuations, which are known to be one of the main sources of decoherence in trapped ion systems. In the final stages of the project, and with the intention of continuing the collaboration between host and researcher, we have been studying the extension of these ideas to other cold molecular systems, such as cold polar molecules, which have been suggested as candidates to achieve quantum information tasks, as well as to study fundamental questions, from parity violation to the time-dependence of physical constants. The training of the Marie Curie Fellow in various problems and techniques of quantum information and quantum simulation has also been an integral part of the project. In this context, the researcher has collaborated in the development of a proposal to directly measure a topological invariant - the Chern number - in a system of cold atoms trapped in a hexagonal optical lattice. Finally, the researcher is currently collaborating in the development of a novel protocol to phase-stabilise a frequency comb.

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