TY - JOUR AU - Széchenyi, Gábor AU - Pályi, András TI - Maximal Rabi frequency of an electrically driven spin in a disordered magnetic field JF - PHYSICAL REVIEW B J2 - PHYS REV B VL - 89 PY - 2014 IS - 11 PG - 5 SN - 2469-9950 DO - 10.1103/PhysRevB.89.115409 UR - https://m2.mtmt.hu/api/publication/2571550 ID - 2571550 N1 - Cited By :23 Export Date: 25 August 2020 CODEN: PRBMD Correspondence Address: Széchenyi, G.; Institute of Physics, Eötvös University, Budapest, Hungary Cited By :23 Export Date: 4 May 2021 CODEN: PRBMD Correspondence Address: Széchenyi, G.; Institute of Physics, Eötvös University, Budapest, Hungary AB - We present a theoretical study of the spin dynamics of a single electron confined in a quantum dot. Spin dynamics is induced by the interplay of electrical driving and the presence of a spatially disordered magnetic field, the latter being transverse to a homogeneous magnetic field. We focus on the case of strong driving, i.e., when the oscillation amplitude A of the electron's wave packet is comparable to the quantum dot length L. We show that electrically driven spin resonance can be induced in this system by subharmonic driving, i.e., if the excitation frequency is an integer fraction (1/2, 1/3, etc.) of the Larmor frequency. At strong driving we find that (i) the Rabi frequencies at the subharmonic resonances are comparable to the Rabi frequency at the fundamental resonance, and (ii) at each subharmonic resonance, the Rabi frequency can be maximized by setting the drive strength to an optimal, finite value. In the context of practical quantum information processing, these findings highlight the availability of subharmonic resonances for qubit control with effectivity close to that of the fundamental resonance, and the possibility that increasing the drive strength might lead to a decreasing qubit-flip speed. Our simple model is applied to describe electrical control of a spin-valley qubit in a weakly disordered carbon nanotube. LA - English DB - MTMT ER - TY - JOUR AU - Hofstetter, L AU - Csonka, Szabolcs AU - Baumgartner, A AU - Fülöp, Gergő AU - d’Hollosy, S AU - Nygård, J AU - Schönenberger, C TI - Finite-Bias Cooper Pair Splitting JF - PHYSICAL REVIEW LETTERS J2 - PHYS REV LETT VL - 107 PY - 2011 IS - 13 PG - 4 SN - 0031-9007 DO - 10.1103/PhysRevLett.107.136801 UR - https://m2.mtmt.hu/api/publication/2668489 ID - 2668489 N1 - Funding Agency and Grant Number: EUEuropean Union (EU); OTKAOrszagos Tudomanyos Kutatasi Alapprogramok (OTKA) [CNK80991]; TAMOP [4.2.1./B-09/1/KMR-2010-2]; Swiss NCCR Nano and NCCR Quantum; Swiss SNFSwiss National Science Foundation (SNSF); Danish Research CouncilsDet Frie Forskningsrad (DFF); Bolyai J. Scholarship; EU ERCEuropean Union (EU)European Research Council (ERC) Funding text: We thank Jens Schindele for fruitful discussions and acknowledge the financial support by the EU FP7 project SE2ND, the EU ERC project CooPairEnt, OTKA CNK80991, TAMOP 4.2.1./B-09/1/KMR-2010-2, the Swiss NCCR Nano and NCCR Quantum, the Swiss SNF, the Danish Research Councils and the Bolyai J. Scholarship for S. C. LA - English DB - MTMT ER - TY - JOUR AU - Hofstetter, L AU - Csonka, Szabolcs AU - Nygard, J AU - Schonenberger, C TI - Cooper pair splitter realized in a two-quantum-dot Y-junction JF - NATURE J2 - NATURE VL - 461 PY - 2009 IS - 7266 SP - 960 EP - 963 PG - 4 SN - 0028-0836 DO - 10.1038/nature08432 UR - https://m2.mtmt.hu/api/publication/2651079 ID - 2651079 N1 - Funding Agency and Grant Number: Swiss National Science FoundationSwiss National Science Foundation (SNSF); Swiss National Center of Competence in Research on Nanoscale ScienceSwiss National Science Foundation (SNSF); Danish Natural Science Research CouncilDanish Natural Science Research Council; Hungarian Scientific Research FundOrszagos Tudomanyos Kutatasi Alapprogramok (OTKA) [NNF 78842]; European UnionEuropean Union (EU) [41139] Funding text: We thank G. Zarand, P. Moca and C. W. J. Beenakker for discussions, and C. B. Srensen and M. Aagesen for Molecular Beam Epitaxy growth. This work was supported by the Swiss National Science Foundation, the Swiss National Center of Competence in Research on Nanoscale Science, the Danish Natural Science Research Council, Hungarian Scientific Research Fund (OTKA) project NNF 78842 and Marie Curie project 41139 of the European Union. S. C. is a grantee of the Bolyai Janos Scholarship. Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland AB - Non-locality is a fundamental property of quantum mechanics that manifests itself as correlations between spatially separated parts of a quantum system. A fundamental route for the exploration of such phenomena is the generation of Einstein-Podolsky-Rosen (EPR) pairs(1) of quantum-entangled objects for the test of so-called Bell inequalities(2). Whereas such experimental tests of non-locality have been successfully conducted with pairwise entangled photons, it has not yet been possible to realize an electronic analogue of it in the solid state, where spin-1/2 mobile electrons are the natural quantum objects(3). The difficulty stems from the fact that electrons are immersed in a macroscopic ground state-the Fermi sea-which prevents the straightforward generation and splitting of entangled pairs of electrons on demand. A superconductor, however, could act as a source of EPR pairs of electrons, because its ground-state is composed of Cooper pairs in a spin-singlet state(4). These Cooper pairs can be extracted from a superconductor by tunnelling, but, to obtain an efficient EPR source of entangled electrons, the splitting of the Cooper pairs into separate electrons has to be enforced. This can be achieved by having the electrons 'repel' each other by Coulomb interaction(5). Controlled Cooper pair splitting can thereby be realized by coupling of the superconductor to two normal metal drain contacts by means of individually tunable quantum dots. Here we demonstrate the first experimental realization of such a tunable Cooper pair splitter, which shows a surprisingly high efficiency. Our findings open a route towards a first test of the EPR paradox and Bell inequalities in the solid state. LA - English DB - MTMT ER - TY - JOUR AU - Csonka, Szabolcs AU - Hofstetter, L AU - Freitag, F AU - Oberholzer, S AU - Schonenberger, C AU - Jespersen, TS AU - Aagesen, M AU - Nygard, J TI - Giant Fluctuations and Gate Control of the g-Factor in InAs Nanowire Quantum Dots JF - NANO LETTERS J2 - NANO LETT VL - 8 PY - 2008 IS - 11 SP - 3932 EP - 3935 PG - 4 SN - 1530-6984 DO - 10.1021/nl802418w UR - https://m2.mtmt.hu/api/publication/2658371 ID - 2658371 LA - English DB - MTMT ER -