Enabling technologies for rare-earth ion quantum memories

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The properties of rare-earth ions in dielectric crystals have made them indispensable in modern optical technologies. Recently, they have also been discovered as very interesting candidates for a number of applications in quantum information processing and quantum communication: the long lifetimes of nuclear spin sublevels allow storage of quantum information for several seconds, while the optical transitions allow fast and flexible manipulation and direct interfacing to ’flying qubits’ and remote units. Realization of this potential requires the selection of a suitable material and the development of the appropriate control techniques. In this project, we will characterize several possible candidate materials and determine their optical and spin Hamiltonian parameters. Using these results, we will develop experimental and theoretical techniques for storing optical quantum states in the material, transferring them to nuclear spin degrees of freedom, and preserving the stored qubits for extended time periods. We will use a combination of laser and radio-frequency magnetic fields for implementing the required control operations. These operations will be optimized for precision and robustness, i.e. they will be insensitive to unwanted variations of control parameters like laser frequency and radio-frequency field amplitude. For this purpose, we will draw on the results achieved in related fields, especially liquid-state nuclear magnetic resonance. The results of this project are expected to have payoffs for the field of quantum information processing and communication, but also for time-resolved magnetic resonance and high resolution laser spectroscopy.