Ulrike Schulz¹, Astrid Bingel¹, Anne Gaertner¹, Nancy Gratzke¹, Thomas Fricke-Begemann², Gregor Matz², Friedrich Rickelt^1
1Fraunhofer Institute of Applied Optics and Precision Engineering IOF, Jena, Germany
²Qioptiq, Goettingen, Germany
The generation and manipulation of “qbits” is the basic requirement for building quantum computers. At present, various ways of generating qubits are being pursued in parallel. One of them are Rydberg atoms which can precisely be trapped to carry out controlled long-range and tunable interactions. Quantum computing experiments with Rydberg atoms require an ultra-high vacuum (UHV) surrounding. A limited number of atoms is extracted from a gas cloud and fixed with optical tweezers. For this experimental setup an UHV fused silica cell has been developed. Various laser beams are focused through the cell walls to the center of the cell. In addition, a newly developed objective will be attached to one of the cell windows to manipulate the atomic states. Highly specialized AR-coatings are in development to address the laser wavelengths from the UV to the NIR spectral range and for the incidence angles according to the geometric requirements. The coatings for demanding phase shift specifications, high light incidence angles and for the curved lens surfaces can essentially be improved by using sub-wavelength nanostructured layers with low effective refractive index as the top-layers of multilayer interference coatings. However, organic vapor deposition materials are used together with silica in the manufacturing process of the nanostructured layers. Carbon containing residuals must be removed as completely as possible after overcoating the structures with silica in order to achieve low absorption values in the UV range and high laser stability. Various procedures were successfully tested for this purpose. The coatings were deposited at first on separate fused silica sheet material. Bonding technologies for fused silica had been developed and tested in parallel. Cleanability, outgassing and mechanical resistance of the nanostructured layers was investigated to define a practical handling procedures for manufacturing the cell. The presentation provides an overview of the surface technologies required to manufacture the cell and the objective lens.