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Prof. Dr. Michael Köhl

Raum 5.020
Wegelerstrasse 8
53115 Bonn 
Tel.: +49-228-73 4899
Fax: +49-228-73 4038

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Ion traps & cavity QED for quantum networks

We use single trapped ions for studies of quantum information processing and the foundations of quantum mechanics. Single ions cooled to the vibrational ground state of a potential constitute a very well controllable quantum system with outstandingly long decoherence times and they formthe building blocks of future quantum computers.







We store and confine single atomic ions in a radio-frequency trap (originally invented at the Physikalisches Institut by W. Paul). A strong oscillating electric quadrupole field generates an oscillating quadrupole potential. We use the technique of laser cooling to cool single ions or small clouds to temperatures in the range of hundreds of Microkelvin. When the temperature of the particles drops below the Coulomb interaction energy the ions arrange into a regular crystalline structure: a Coulomb crystal. The spacing between the ions in the crystal is on the order of 10 microns thus the individual ions can be resolved and addressed. This provides a promising avenue for quantum computation with many qubits.

Single Ion Coupled to an Optical Fiber Cavity

Phys. Rev. Lett. 110, 043003 (2013)

iontrap cavityWe present the realization of a combined trapped-ion and optical cavity system, in which a single Yb+ ion is confined by a micron-scale ion trap inside a 230 micrometer-long optical fiber cavity. We characterize the spatial ion-cavity coupling and measure the ion-cavity coupling strength using a cavity-stimulated transition. Owing to the small mode volume of the fiber resonator, the coherent coupling strength between the ion and a single photon exceeds the natural decay rate of the dipole moment. This system can be integrated into ion-photon quantum networks and is a step towards cavity quantum electrodynamics based quantum information processing with trapped ions.



Dr. Robert Maiwald, Dr. Hendrik Meyer, Jonathan Silver, Leonardo Carcagni, Tim Ballance



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