Browsing by Subject "Two-level system"

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Open Access
Bounding the Set of Finite Dimensional Quantum Correlations
(American Physical Society, 2015) Navascués, M.; Vértesi, T.
We describe a simple method to derive high performance semidefinite programing relaxations for optimizations over complex and real operator algebras in finite dimensional Hilbert spaces. The method is very flexible, easy to program, and allows the user to assess the behavior of finite dimensional quantum systems in a number of interesting setups. We use this method to bound the strength of quantum nonlocality in Bell scenarios where the dimension of the parties is bounded from above. We derive new results in quantum communication complexity and prove the soundness of the prepare-and-measure dimension witnesses introduced in Gallego et al., Phys. Rev. Lett. 105, 230501 (2010). Finally, we propose a new dimension witness that can distinguish between classical, real, and complex two-level systems. © 2015 American Physical Society. © 2015 American Physical Society.
Open Access
An experimental approach to nanomechanical buckling and snap-through phenomenon
(2019-08) Hatipoğlu, Utku
Buckling has received little attention as a valuable resource for engineering applications since it is regarded as a type of failure in civil and mechanical engineering. Nevertheless, buckling has a great potential in nanoelectromechanical systems(NEMS) field as a bistable process that has rich and complex dynamics. Here, we explore post buckling dynamics of a nano-beam experimentally by employing various probing techniques. By employing an all-electronic architecture, we precisely control the buckling amount as well as buckling direction of the nano-beam which eventually gives us the ability to control a two-level mechanical system with high precision and speed. A full control over the potential energy landscape of the system is demonstrated with different techniques such as Scanning Electron Microscopy operated in three different modes and microwave coupling method. During proof of concept experiments, left and right buckling, large deflection buckling, nonvolatility – which is an indication of pure bistable states – and snap-through phenomenon is demonstrated. Further steps of the study focused on the snap-through phenomenon that is the interstate transitions of the buckling beam after bifurcation. During these experiments, more involved relations are investigated such as mechanical bias and effect of plastic deformation as well as the effect of actuation scheme on interstate jumps. Moreover, to obtain a better grasp of post-buckling dynamics, quantitative measurements are carried out which reveal the reaction speed of the system and time scale of interstate jumps. Lastly, oscillatory snap-through motion is observed in some special conditions that can be beneficial to understand noise dynamics of the system and it has a potential to contribute energy harvesting applications.