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Development of a pan-European Microtrap Technology capability for Trapped Ion Quantum Information Science

Exploitable results

Microtrap is a Strep project developing an EU technology capability in trapped ion microstructures for application to quantum information science. The major experimental advances in quantum information science over the last decade have all been demonstrated in mesoscopic trapped ion systems, and include qubit operation, deterministic entanglement, basic quantum algorithm demonstration, quantum gate operation and quantum state teleportation. Already, trapped ion technology has been shown capable to meet Di Vincenzo criteria for viable quantum computing. These address qubit initialisation, qubit read-out, universal quantum gates, scalability and long coherence times. The last two are critical for achieving an architecture allowing many qubit interactions and thereby capable of competing with CMOS-based computing power. This project targets scalability through miniaturization of trapped ion architectures, allowing quantum logic manipulation of ion arrays whilst minimising decoherence through environmental perturbation. The consortium of Microtrap partners comprise six major trapped ion groups from UK, Austria, Denmark and Germany, and include the leading European experimental trapped ion QIP researchers. This consortium of partners is focused on European micromachining and microfabrication capability to design, develop and test micro-trap architectures. The Microtrap project goal targeted the supply and test of microtrap devices with optimised microtrap materials, trap design and fabrication processes, organised within standard chip mounting architectures. Objectives for the latter part of the project were to test fabricated microtraps for suitability as QIP devices through measurement of ion cooling and heating rates and decoherence, and demonstration of ion shuttling capability, entanglement and gate operations and the potential for scalability. The outputs of the project represent a major step forward in integrating QIP into microelectronics technology, bridging the gap between large, complex laboratory demonstrations and viable microtrap chips. Three microtrap design architectures were pursued during the course of the project. Two designs of three-dimensional traps were investigated; the first was based on gold-coated ceramic wafers, the second on gold-coated silica-on-silicon wafers. The ceramic wafer microtrap has been used to demonstrate several QIP techniques such as sideband cooling, ion transport and Ramsey spectroscopy. In the latter half of the project, gold-on-quartz two-dimensional (surface) traps were also designed, fabricated and operated. We have also achieved a range of techniques for microtrap mounting on industry-standard chip carriers, allowing easy-access chip connectivity into the ultra-high-vacuum environment needed for the microtrap, and interfacing directly with standard micro-electronics design. This is a 'lab-on-a-chip' approach, but with control and manipulation of the quantum state. Microtrap developed within this project have undergone the initial stages in evaluating suitability for quantum information applications. The all-important parameters of heating and associated decoherence rates have been measured for some of the fabricated microtraps. Elementary operations required for entanglement and gates, such as coherent spectroscopy and precisely controlled ion transport, have also been demonstrated. In achieving this, the project has made significant progress in addressing the scalability challenge that underpins viable trapped ion quantum information processing. Collaborations within and beyond the Microtrap consortium has included two-day workshops, invited seminars and presentations at relevant international conferences. Microtrap workshops were held every six months at NPL (2006), Ulm and Innsbruck (2007), Siegen and Aarhus (2008) and Oxford (2009), together with a trapped ion workshop satellite meeting to ICAP in Innsbruck (July 2006). These enabled critical review of partner activities and crystallised forward thinking. A brief description of the Microtrap project together with highlights of the results can be found on the Microtrap website ( www.microtrap.eu).