Rydberg Excited Calcium Ions for Quantum Interactions

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Project details

Email: Igor [dot] Lesanovsky [at] nottingham [dot] ac [dot] uk

University of Nottingham
Website: http://www.nottingham.ac.uk/~ppziwl/rion/
Project description

Trapped cold ions are among the most advanced systems to implement quantum information processing. In current experiments entanglement of the qubits, represented by long lived internal atomic states, is achieved via quantum control of the (collective) motion of the ion crystal. Instead, we propose an unprecedented experimental program supported by theory, where the huge dipole moments associated with Rydberg excited ions are the basis of extremely strong spin-dependent long range interactions, and thus exceptionally fast entangling operations as basic building blocks for quantum computing and quantum simulation. While in the short term the fundamental questions to be explored are the understanding of Rydberg excitation and dynamics of single and multiple ions stored in linear Paul traps, and the various ways of manipulating this dynamics with external electromagnetic fields, the long term promise of this project is a potentially scalable very fast ion trap quantum processor, and in particular also a novel efficient quantum simulator of spin models, for Heisenberg type interactions to exotic matter with topological phases. A main experimental challenge is the requirement of a coherent light source near 122nm for the ion Rydberg excitation. Our consortium is in the remarkable and unique situation where in a single laboratory both these coherent light sources as well as advanced ion quantum computing setups are available, thus allowing us to explore this extremely promising new frontier of Rydberg ion quantum information processing on a comparatively short time scale. The planned experiments will be based on the well established techniques of ion trapping, quantum state detection and manipulation with laser fields. An adapted quantum shelving method is proposed to detect transitions to Rydberg states with unity detection efficiency on individual ions even in large crystals. Initially we will accurately determine energy levels and atomic properties of ion Rydberg states, and then we aim for mutual Rydberg state interactions of adjacent ions. Such gate interactions, Rydberg induced quantum phase transitions and a full tomography of the resulting quantum state benefit from the highly developed schemes in quantum information processing. In the future, beyond the experimental horizon of the three-year project, fast Rydberg ion quantum logic operations could possibly be combined with the conventional gate schemes and modern ion trap technology.