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Abstract:

Quantum secret sharing is a protocol for secure communication between several parties in a way that messages can be retrieved only by collaboration of all of the parties. Naturally entangled states have been used for sharing such secret keys. Since entangled states are very hard to prepare and are very fragile, there have been some attempts to remove entanglement from these protocols. Here we review some of the recent protocols which are not based on entangled states and present also our recent results on non-entangled quantum secret sharing in arbitrary dimensions.


Abstract:

Quantum simulators are certain quantum systems which emulate the behavior of another system with higher controllability and precision. They are the first step towards realization of universal quantum computers. So far, cold atoms and ions have been predominantly exploited for serving as quantum simulators thanks to their high controllability and long coherence times. Nevertheless, any solid state effects cannot be easily simulated by such systems, take spin-orbit interaction as an example. Therefore, having a solid state based quantum simulator is very desirable. We propose quantum dot arrays and electronic Wigner crystals in 1D quantum wires for serving as quantum simulators. In particular, we focus on realization of the ground state of the Heisenberg spin chain in realistic experimental conditions. Furthermore, we provide an effective method for the certification of our quantum simulator via singlet-triplet measurements. As an application for the quantum simulator, we propose both quantum dot arrays and Wigner crystals in quantum wires for transferring quantum information across long distances through their non-equilibrium dynamics.


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I briefly review the resource based view to quantum coherence and its measures. Then I will introduce the concepts of cohering and decohering powers for a quantum channel. By presenting some examples I will argue that although the calculation of these quantities require optimizations, they are well defined and can be calculated. Contrary to a view at first sight, quantum channels can have non zero cohering power. Finally I will talk about some recently related works on cohering and decohering power.


Abstract:

Erwin Schrödinger was always frustrated by the apparent quantum jumps and collapses in quantum systems subject to measurement, and as late as in 1952, he declared the mere idea of doing experiments with single quantum particles “as absurd as the one of raising Ichthyosauria in the Zoo”. On this subject Schrödinger was wrong, and a variety of single quantum systems are now available for experimental investigation. Schrödinger may have been terrified to know that these systems are now candidates for applications in crucial technologies such as quantum information and quantum metrology. In this talk, I shall review theoretical methods to describe, control and understand the behavior of these Ichthyosauria in the quantum laboratory and show examples of how we can even benefit from their random quantum jump behavior.


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Miniaturization of electronic devices is rapidly approaching the atomic scale. Hence, building subnano (or nano) scale circuit components and controlling their interconnect behavior is of paramount importance. An excellent candidate for this purpose is the use of dangling bonds. In recent years, dangling bonds (DB) were introduced as truly atomic-scale quantum dots with their energy state located within the semiconductor bandgap. Dangling bonds can be selectively created and manipulated using nanodevices such as a scanning tunneling microscope. A few years ago, it was shown experimentally that if two DBs are created close enough to each other on a hydrogen-terminated Si(100) surface they display coupling behavior. A set of coupled dangling bonds has the potential to offer a novel template for designing planar nanostructures and nanoscale circuits. In this presentation, the main focus is on characterization of coupled dangling-bond pairs located on the hydrogen-terminated silicon(100) surface. We show that the coupling strength depends strongly on the structure of the silicon surface and the location and orientation of DBs’ orbitals. Coupled DBs can be employed as the building blocks for construction of nanosystems, such as DBs nano- and sub-nanowires, quantum-cellular-automata cells, and quantum computing schemes.


 

 

 

              

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