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Fortágh József

CQ Center for Collective Quantum Phenomena and their Applications
University of Tübingen
Auf der Morgenstelle 14, D-72076 Tübingen, Germany

Interfacing cold atoms and solids

Trapping and manipulating atoms by means of microscopic traps has seen
enormous advances within the last decade. Today, ultra-cold atom
clouds, Bose-Einstein condensates, and Fermi gases are routinely
trapped in conservative potential at the surface of microchips [1].
Such experiments have delivered important insights into fundamental
interactions between atoms and surfaces and pave the way towards the
coherent coupling between atoms and quantum electronic circuits.

In our experiments, we investigate the quantum interface between
atomic clouds and superconducting devices. In general, the state of a
superconducting quantum bit can be manipulated at microelectronic
rates. However, its decoherence is fast due to the coupling to the
thermal environment. Transferring the quantum state to cold atoms as
quantum memory may bridge sort and long time scales. We develop
experimental techniques towards the realization of such solid
state-atomic-light quantum interfaces. I report the realization of a
trapped rubidium atomic clock on a superconducting chip. We use the
atomic clock to demonstrate the long coherence time of atomic
superposition states near the superconductor, which is necessary for
constructing a long living quantum memory [2].

Another subject of our research is the development of integrated
quantum sensors based on ultra-cold atoms. I describe the application
of ultra-cold atom clouds as the “tip” of a scanning probe microscope
[3]. This tip (typically 103–105 atoms, density 1012–1014 cm-3,
temperature 10nK–1ľK) is scanned in a three-dimensional volume above
the surface of interest by means of a magnetic “conveyor belt”. Analog
to AFMs, the cold-atom scanning probe microscope (CA-SPM) can be
operated in contact and dynamical modes for imaging surface
topographies and for ultrasensitive force measurements [4].

1. J. Fortágh, C. Zimmermann, “Magnetic microtraps for ultracold atoms”,
Reviews of Modern Physics 79, 235 (2007).
2. S. Bernon et al., arXiv:1302.6610 (2013).
3. M. Gierling et al., “Cold-atom scanning probe microscopy”,
Nature Nanotechnology 6, 446-451 (2011).
4. P. Schneeweiß et al., “Dispersion forces between ultracold atoms
and a carbon nanotube”,
Nature Nanotechnology 7, 515-519 (2012)

Az előadás kezdete: április 2-án, kedden kettőkor

helye: ELTE TTK északi épület, 5.128-as terem.

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2013.04.13. 14:00