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Content archived on 2024-05-24

Quantum Gates and Elementary Scalable Processors Using Deterministically Addressed Atoms

Objective

Considerable efforts are being made worldwide to realize a scalable quantum information processor, using a wide range of competing technologies. Among these technologies, single individually addressed trapped atoms and ions, as well as Rydberg atoms in microwave cavities, represent some of the most promising systems in which to perform the kind of quantum state manipulations required. We will use these techniques to work towards the demonstration of elementary quantum processors. Special attention will be given to elementary scalability, i.e. either to the operation of a moderate number of qubits in a single processor, or to the interconnection of several processors at the quantum level. Such interconnections will be mediated through the exchange of material particles (atoms or ions). We will operate and assess the fidelity of quantum gates in our systems. Our project includes a range of theory activities in support of the experiments. Considerable efforts are being made worldwide to realize a scalable quantum information processor, using a wide range of competing technologies. Among these technologies, single individually addressed trapped atoms and ions, as well as Rydberg atoms in microwave cavities, represent some of the most promising systems in which to perform the kind of quantum state manipulations required. We will use these techniques to work towards the demonstration of elementary quantum processors. Special attention will be given to elementary scalability, i.e. either to the operation of a moderate number of qubits in a single processor, or to the interconnection of several processors at the quantum level. Such interconnections will be mediated through the exchange of material particles (atoms or ions). We will operate and assess the fidelity of quantum gates in our systems. Our project includes a range of theory activities in support of the experiments.

OBJECTIVES
We will work with individually addressable atoms and ions held in a range of different types of trap. We will use these systems to create quantum gates and to investigate their fidelity. We will design, build and operate a new generation of trapping geometries using a wide range of techniques but sharing a common feature: they will allow the interaction and coherent transport of individual atoms and ions between controlled trapping sites with the goal of realizing an 'elementary scalable processor'. We will furthermore employ the methods of cavity QED. Using Rydberg atoms in microwave cavities we will demonstrate quantum gates, realize simple quantum algorithms and perform demonstrations of error correction codes. Optical cavity QED methods will be used to entangle trapped atoms and ions using cavity-mediated collisions. We will also explore a range of other methods through which neutral atom entanglement may be achieved. Theoretical studies will complement the experimental work.

DESCRIPTION OF WORK
We will work towards quantum information processing (QIP) using trapped ions, trapped atoms and cavity QED (CQED) techniques. Using trapped ions we will demonstrate quantum gate operation according to the Cirac-Zoller proposal and preparation and detection of Bell- and GHZ-states. We will conduct fidelity analysis of quantum gates and perform gate tomography. We will develop miniature ion trapping structures that consist of interconnected traps. We plan to study the coherent transport of ions in these structures with the goal of achieving the transfer of entanglement between traps, hence demonstrating a scalable model for QIP. One group will apply techniques successfully demonstrated in NMR, to trapped ions. We will also implement a recent proposal for a new type of quantum gate, which places less severe requirements on the cooling. One group will demonstrate continuous sympathetic cooling of 25Mg+ ions with In+ ions embedded in the string, which should enable greatly extended gate sequences. We will study a range of quantum information processing realizations based on different types of neutral atom traps including microscopic dipole traps, atomic conveyor belts, atom-chips and optical lattices. We will investigate a number of schemes that have been proposed for entangling neutral atoms including "conditional quantum state control"' We will also study the possibilities of using microensembles, atomic nano-clouds and small Bose-Einstein condensates for QIP. Using CQED techniques we aim to realize simple quantum algorithms or demonstrations of error correction codes. We also plan to develop a deterministic single Rydberg atom source. The methods of optical CQED will be used to generate entanglement between neutral atoms and between ions held inside high-Q cavities and the normal-mode splitting of the coupled atom-cavity system will be used to read out the atomic states. Theoretical work will underpin the experiments and provide extra links between the themes.

Call for proposal

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Coordinator

IMPERIAL COLLEGE OF SCIENCE, TECHNOLOGY AND MEDICINE
EU contribution
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Total cost
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Participants (15)