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Entanglement Detection by Current Measurements in Double Quantum Dot System

100%
Busz P., Rożek P., Tomaszewski D., Martinek J.
Acta Physica Polonica A
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2015
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vol. 127
|
issue 2
490-492
EN
The development of quantum computing in quantum dots systems requires highly efficient and continuous solid-state source of spatially separated spin-entangled electrons. One of the approaches is a use of double quantum dot system connected to superconducting lead, where Cooper pairs provide a source of naturally entangled electrons. Apart from the source, an useful tool for detection of quantum entanglement is needed. We present entanglement detection by the ferromagnetic electrodes using entanglement witness operator method and direct measurement of spin polarized current in the system. We investigate requirements that have to be fulfilled by ferromagnetic detectors.
2
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An Influence of Silicon Substrate Parameters on a Responsivity of MOSFET-Based Terahertz Detectors

76%
Kucharski K., Zagrajek P., Tomaszewski D., Panas A., Głuszko G., Marczewski J., Kopyt P.
Acta Physica Polonica A
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2016
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vol. 130
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issue 5
1193-1195
EN
Silicon n-channel MOS transistors are a promising solution for sub-terahertz radiation detection. Their sensitivity is strongly related to the device construction. A type and thickness of the device substrate are key parameters affecting the responsivity, because the silicon substrate is a medium for the radiation propagation and the radiation energy loss, which degrades the detection efficiency. This work is aimed at analysis of the silicon substrate characteristics effect on operation of the MOSFETs as the terahertz radiation sensors. A manufacturing of the MOSFETs on three different substrate types including changing the substrate thickness is described in the paper. Next, the fabricated devices were exposed to THz radiation and their photoresponses were measured. It may be concluded that MOSFETs on silicon-on-insulator wafers with locally thinned substrates demonstrate the highest photoresponse. However, the experiments with the MOSFETs on high resisivity wafers give also promising results.
3
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Terahertz Photovoltaic Response of Si-MOSFETs: Spin Related Effect

64%
Videlier H., Dyakonova N., Teppe F., Consejo C., Chenaud B., Knap W., Lusakowski J., Tomaszewski D., Marczewski J., Grabiec P.
Acta Physica Polonica A
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2011
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vol. 120
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issue 5
927-929
EN
We report on investigations of photovoltaic response of Si-MOSFETs subjected to terahertz radiation in high magnetic fields. Then a DC drain-to-source voltage is developed that shows singularities in magnetic fields corresponding to paramagnetic resonance conditions. These singularities are investigated as a function of incident frequency, temperature and two-dimensional carrier density. We tentatively attribute these resonances to spin transitions of the electrons bound to Si dopants and discuss the possible physical mechanism of the photovoltaic signal generation.
4
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Entanglement Detection with Non-Ideal Ferromagnetic Detectors

64%
Rożek P., Busz P., Kłobus W., Tomaszewski D., Grudka A., Baumgartner A., Schönenberger C., Martinek J.
Acta Physica Polonica A
|
2015
|
vol. 127
|
issue 2
493-495
EN
Entangled states are essential in basics quantum communication protocols and quantum cryptography. Ferromagnetic contacts can work as a spin detector, giving possibility of converting information about electron spin to the electric charge, and therefore, detection of entangled states with the electric current measurements is possible. Method of confirming entanglement with non-ideal detectors is presented, the impact of decoherence and noise on states and quality of entanglement is discussed. Entanglement witness (EW) operator method is compared with the CHSH inequalities approach. Required spin polarization for the EW is lower than for the CHSH inequalities. System with asymmetric spin polarizations of detectors was analyzed, including the CHSH inequalities and the EW method.
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