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Research Center for Quantum Information
Institute of Physics, Slovak Academy of Sciences
Dúbravská cesta 9, 84511 Bratislava, Slovakia
Tel: (+421 +2) 20910701
Fax: (+421 +2) 5477-6085
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N E W S | old news |
  2.7.2015 Research publication
Exploring boundaries of quantum convex structures: Special role of unitary processes
We address the question of finding the most unbalanced convex decompositions into boundary elements (so-called boundariness) for sets of quantum states, observables, and channels. We show that in general convex sets the boundariness essentially coincides with the question of the most distinguishable element, thus providing an operational meaning for this concept. Unexpectedly, we discovered that for any interior point of the set of channels the most unbalanced decomposition necessarily contains a unitary channel. In other words, for any given channel the most distinguishable one is some unitary channel. Further, we prove that boundariness is submultiplicative under the composition of systems and explicitly evaluate its maximal value that is attained only for the most mixed elements of the considered sets.
by Zbigniew Puchała, Anna Jenčová, Michal Sedlák, and Mário Ziman
Phys. Rev. A 92, 012304 (2015) |+++|
QUICOST (VEGA 2/0125/13), MP1006 COST Action
  18.5.2015 Research publication
Generation and Detection of Spin Currents in Semiconductor Nanostructures with Strong Spin-Orbit Interaction
Storing, transmitting, and manipulating information using the electron spin resides at the heart of spintronics. Fundamental for future spintronics applications is the ability to control spin currents in solid state systems. Among the different platforms proposed so far, semiconductors with strong spin-orbit interaction are especially attractive as they promise fast and scalable spin control with all-electrical protocols. Here we demonstrate both the generation and measurement of pure spin currents in semiconductor nanostructures. Generation is purely electrical and mediated by the spin dynamics in materials with a strong spin-orbit field. Measurement is accomplished using a spin-to-charge conversion technique, based on the magnetic field symmetry of easily measurable electrical quantities. Calibrating the spin-to-charge conversion via the conductance of a quantum point contact, we quantitatively measure the mesoscopic spin Hall effect in a multiterminal GaAs dot. We report spin currents of 174 pA, corresponding to a spin Hall angle of 34%.
by Fabrizio Nichele, Szymon Hennel, Patrick Pietsch, Werner Wegscheider, Peter Stano, Philippe Jacquod, Thomas Ihn, and Klaus Ensslin
Phys. Rev. Lett. 114, 206601 (2015) |+++|
S E M I N A R S | more |
25/08 10:30
Vahid Karimipour (Tehran)
Quantum secret sharing without entanglement
V I S I T O R S | history |


24.08-28.08 Vahid Karimipour
(Sharif University of Technology, Tehran, Iran)






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