One of the more interesting advances in science is the use of the atom chip. As the demands of technology require smaller and smaller components, studying the fundamentals of physics at the quantum level will become increasingly important. The Munich Atom Chip Group, under the direction of Theodor H盲nsch at the University of Munich and the Max-Planck-Institute of Quantum Optics is working to find ways to learn more about physics at the most fundamental levels.

鈥淲e have studied in detail whether it is possible to prepare cold atoms close to a solid state chip surface without losing coherence properties,鈥� Philipp Treutlein, a member of the research group, tells 麻豆淫院Org.com. 鈥淲e showed that it is possible to prepare coherent superpositions of atomic quantum states at only a few micrometers distance from a solid surface.鈥� The next step, he says, is to 鈥減ut something interesting on the surface and see how it will interact with the atoms, and whether the interaction reveals quantum effects.鈥�

The result? A hybrid quantum system that would allow physicists to explore interactions between solid state systems and quantum optical systems 鈥� and possibly lead to other, more specific applications. Treutlein and his coauthors, David Hunger, Stephan Camerer and Theodor H盲nsch from the University of Munich, as well as Jakob Reichel at the Kastler Brossel Laboratory in Paris, discuss their theory in a piece titled, 鈥淏ose-Einstein Condensate Coupled to a Nanomechanical Resonator on an Atom Chip,鈥� published in 麻豆淫院ical Review Letters.

Treutlein emphasizes that right now this hybrid quantum system is at the theoretical stage. 鈥淲e are experimentalists, though,鈥� he says, 鈥渁nd we are working with the solid-state physics group of Professor [J枚rg] Kotthaus to get it to work in the laboratory.鈥�

The hybrid system the group is investigating is composed of Bose-Einstein condensed atoms and a nanomechanical cantilever resonator. 鈥淲e take a small cantilever, a nano-sized cantilever, and put a small magnet on the tip. When the cantilever vibrates, it shakes the magnet, and thus generates an oscillatory magnetic field. This oscillatory field couples to the spin of the atoms which are hovering above the cantilever tip, inducing spin flips,鈥� Treutlein explains. 鈥淭he spin flips are the signal which we will detect, and they give us information about the coupling鈥� between the solid-state cantilever and the atoms.

Treutlein believes there is potential for future applications of this work. 鈥淲e鈥檙e only at the very beginning of exploring this system experimentally,鈥� he points out. 鈥淲hen we see what the fundamental dynamics are, and whether it works, we can decide on specific applications.鈥� But he does think that such hybrid systems could be useful sensors for magnetic fields.

He also thinks that there is some potential for quantum information processing. 鈥淎n atomic system has very good coherence properties, but the dynamics are slow. In solid state systems, the dynamics are faster, but the coherence is washed out in a shorter time. Maybe atoms could be used as quantum memory and the solid state system as a fast quantum processor.鈥� Treutlein pauses and then laughs. 鈥淏ut I鈥檓 not sure yet if that would work. Our main focus isn鈥檛 really on building a quantum computer.鈥�

But what he and his colleagues are building is interesting enough on its own. 鈥淭his hybrid quantum system, if it works like we think it will, would give us great insight into fundamental physics.鈥� In an email, Treutlein expounds: 鈥淔or example, we would like to see whether one can use the Bose-Einstein condensate, composed of a few thousand atoms, to engineer the quantum state of the resonator, composed of several billions of atoms, and how such a large quantum system behaves.鈥�

The work has its challenges, though. 鈥淲e have to be able to prepare the mechanical oscillator at very low temperatures to see quantum effects. And we have to combine the state of the art technology from quantum optics and solid-state physics, which is very challenging,鈥� Treutlein admits. 鈥淲e are looking into the long-term here.鈥�

鈥淓ven though we鈥檝e proposed a theory,鈥� he explains, 鈥渨e mostly work experimentally, so we see both sides. We know how difficult this might be to realize in the laboratory. But it also means that we try very hard to make realistic assumptions.鈥�

He continues: 鈥淚t seems to us that we could make such a hybrid quantum system a reality. But it doesn鈥檛 mean it鈥檚 easy.鈥�

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