AtomChip: Development, Application as a Magnetic Field Probe

Neutral atoms can be trapped and guided using microfabricated devices we call AtomChips. These chips form the basis for robust and versatile applications of cold atoms ranging from atom optics to fundamental questions in mesoscopic physics. The project aims at a truly integrated chip for robust quantum manipulation and quantum limited detection of neutral atoms. With these we will further develop the BEC magnetic microscope. This method provides unique and precise information about magnetic potentials. The diversified fabrication capability and newly developed robust integration in a modular experiment will allow the BEC microscope to become a tool which will enable us to study different materials and structures, ranging from thin metal wires to semiconductor quantum wells and supercurrents.

The special emphasis of the project was scientific and technological development of fabricating and implementing AtomChips and thereby lay the foundations for several other national and international projects. In close cooperation with the Center for Micro- and Nanostructures (ZMNS) at the TU Wien the technology of AtomChips was established and further developed, both for normal and superconducting structures. Special emphasis was given to the emerging field of hybrid quantum systems where the atom chip is an ideal platform to connect spin ensembles to superconducting micro wave circuits. There we have developed and implemented superconducting AtomChips and high finesse co-planar micro wave resonators. In a different line of work we developed further the experiments where the AtomChips are implemented. We developed and adapted stochastic optimization methods for cold atom experiments which allow us now to find optimal experimental conditions by automatic search. In parallel we developed a novel cryogenic AtomChip experiment where the atoms are transported into a cryostat by moving magnetic traps. The latter setup was designed so that it can be implemented in a dilution refrigerator. This opens up the possibility to bring atoms into the T<100mK environment needed for superconducting quantum circuits, an essential prerequisite to implement hybrid quantum systems combining ultra cold atoms and superconducting circuits. In parallel we developed a new testing setup for evaluating the AtomChips before they are implemented in the experiments. In the experiments their performance was then tested with the magnetic field microscope. Scientific and technological progress in the last decades has proven that miniaturization and integration are important steps towards the robust application of fundamental physics. Prominent examples are semiconductor physics and its application in integrated circuits and information processing, or optics and the development of integrated micro-optical devices, and their application in sensor- and communication technology. AtomChips aim at a similar step for quantum optics and atomic physics systems: building a cornerstone of a quantum technology with the help of miniaturizing and integration. AtomChips combine the best of two worlds: the ability to use cold atoms - a system well suited for precise quantum manipulation - and the technological capabilities of nanofabrication. To build this quantum toolbox, the AtomChip must be able to perform numerous functions which put extreme demands on component fabrication and integration techniques.