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CeNS Colloquium

Place: Kleiner Physik-Hörsaal, Geschwister-Scholl-Platz
Date: 25.06.10, Time: 15:30 h

Cooper-Pair Splitter: towards a source of entangled electrons

Prof. Christian Schönenberger
Department of Physics, Universität Basel

In quantum physics pairs of entangled particles, so called Einstein-Podolsky-Rosen (EPR) pairs, play a special role as toy objects for fundamental studies. Whereas EPR pairs of photons can be generated by parametric down conversion (PDC) in a crystal, a similar source for EPR pairs of electrons does not exist yet. In several theory papers, it has been suggested to use a superconductor for this purpose. The superconducting ground state is formed by a condensate of Cooper-pairs which are electron pairs in a spin-singlet state. Since there are many Cooper pairs in a metallic superconductor like Al, the main task is to extract Cooper pairs one by one and to split them into different arms. This has recently been demonstrated by two groups [1,2] using hybrid quantum-dot devices with both superconducting and normal metal contacts. The quantum dots were realized in semiconducting nanowires [1] and carbon nanotubes [2]. In this talk, I will start with experiments on Cooper-pair splitting in metallic devices and then dwell on the recent studies of Cooper-pair splitting using quantum dots.

 

References:

[1] L. Hofstetter, S. Csonka, J. Nygard, and C. Schönenberger, Cooper pair splitter realized in a two-quantum-dot Y-junction, Nature 460, 906 (2009)
[2] L.G. Herrmann, F. Portier, P. Roche, A. Levy Yeyati, T. Kontos, and C. Strunk, Carbon Nanotubes as Cooper Pair Beam Splitters, Phys. Rev. Lett. (2010)