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Van der Wal, C. (author)This thesis presents experimental research on Josephson junction devices that behave quantum mechanically. The devices are formed by micrometer-sized superconducting islands, that are interconnected by a Josephson tunnel junction: a thin insulating layer between two superconductors. With current microfabrication technology it is possible to make...doctoral thesis 2001
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Han, J. (author)The progress in CMOS technology has entered the sub-micron realm, and the technology will approach its limits within about 15 years. Already various novel information processing devices, based on quantum mechanical effects at the nanometer scale, have been widely investigated and some have been successfully demonstrated at the circuit level....doctoral thesis 2004
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Eroms, J. (author), Van Schaarenburg, L.C. (author), Driessen, E.F.C. (author), Plantenberg, J.H. (author), Huizinga, C.M. (author), Schouten, R.N. (author), Verbruggen, A.H. (author), Harmans, C.J.P.M. (author), Mooij, J.E. (author)The authors have studied low-frequency resistance fluctuations in shadow-evaporated Al/AlOx/Al tunnel junctions. Between 300 and 5?K the spectral density follows a 1/f law. Below 5?K, individual defects distort the 1/f shape of the spectrum. The spectral density decreases linearly with temperature between 150 and 1?K and saturates below 0.8?K....journal article 2006
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Plantenberg, J.H. (author)This thesis presents results of theoretical and experimental work on superconducting persistent-current quantum bits. These qubits offer an attractive route towards scalable solid-state quantum computing. The focus of this work is on the gradiometer flux qubit which has a special geometric design, that both provides a stable phase bias and...doctoral thesis 2007
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Koppens, F.H.L. (author)An electron does not only have an electric charge, but also a small magnetic moment, called spin. In a magnetic field, the spin can point in the same direction as the field (spin-up) or in the opposite direction (spin-down). However, the laws of quantum mechanics also allow the spin to exist in both states at the same time (so-called...doctoral thesis 2007
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Ashhab, S. (author), Niskanen, A.O. (author), Harrabi, K. (author), Nakamura, Y. (author), Picot, T. (author), De Groot, P.C. (author), Harmans, C.J.P.M. (author), Mooij, J.E. (author), Nori, F. (author)We consider a system composed of two qubits and a high excitation energy quantum object used to mediate coupling between the qubits. We treat the entire system quantum mechanically and analyze the properties of the eigenvalues and eigenstates of the total Hamiltonian. After reproducing well known results concerning the leading term in the...journal article 2008
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Wei, H. (author), Nazarov, Y.V. (author)We address continuous weak linear quantum measurement and argue that it is best understood in terms of statistics of the outcomes of the linear detectors measuring a quantum system, for example, a qubit. We mostly concentrate on a setup consisting of a qubit and three independent detectors that simultaneously monitor three noncommuting operator...journal article 2008
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Zwanenburg, F.A. (author)The research in this thesis is motivated by an interest in quantum physics and by the prospect of new applications based on the spin of electrons or holes. This work focuses on confining single spins in quantum dots, which can serve as building blocks of a future quantum computer. Such a computer exploits the unique features of quantum mechanics...doctoral thesis 2008
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Picot, T. (author), Lupa?cu, A. (author), Saito, S. (author), Harmans, C.J.P.M. (author), Mooij, J.E. (author)We analyze the relaxation of a superconducting flux qubit during measurement. The qubit state is measured with a nonlinear oscillator driven across the threshold of bifurcation, acting as a switching dispersive detector. This readout scheme is of quantum nondemolition type. Two successive readouts are used to analyze the evolution of the qubit...journal article 2008
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Vink, I.T. (author)Besides an electric charge, electrons also have a tiny magnetic moment, called spin. In a magnetic field, the spin has two possible orientations: 'spin-up' (parallel to the field) and 'spin-down' (anti-parallel to the field) and can therefore be used as a quantum bit, the computational unit of a quantum computer. For quantum computations,...doctoral thesis 2008
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Gühne, O. (author), Bodoky, F. (author), Blaauboer, M. (author)We present a method to determine the decay of multiparticle quantum correlations as quantified by the geometric measure of entanglement under the influence of decoherence. With this, we compare the robustness of entanglement in Greenberger-Horne-Zeilinger (GHZ), cluster, W, and Dicke states of four qubits and show that the Dicke state is the...journal article 2008
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Bodoky, F. (author)The goal of this thesis is to investigate theoretically the generation and behaviour of multipartite entanglement for solid-state nanosystems, in particular electron spin quantum bits (so-called 'qubits') in quantum dots. A quantum dot is a tiny potential well where a single electron can be trapped. A quantum bit can be implemented in this...doctoral thesis 2009
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- Nowack, K.C. (author) doctoral thesis 2009
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Verduijn, J. (author), Tettamanzi, G.C. (author), Lansbergen, G.P. (author), Collaert, N. (author), Biesemans, S. (author), Rogge, S. (author)In this letter, we describe the observation of the interference of conduction paths induced by two donors in a nanoscale silicon transistor, resulting in a Fano resonance. This demonstrates the coherent exchange of electrons between two donors. In addition, the phase difference between the two conduction paths can be tuned by means of a magnetic...journal article 2010
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De Groot, P.C. (author), Van Loo, A.F. (author), Lisenfeld, J. (author), Schouten, R.N. (author), Lupa?cu, A. (author), Harmans, C.J.P.M. (author), Mooij, J.E. (author)We present experimental results on the crosstalk between two ac-operated dispersive bifurcation detectors, implemented in a circuit for high-fidelity readout of two strongly coupled flux qubits. Both phase-dependent and phase-independent contributions to the crosstalk are analyzed. For proper tuning of the phase the measured crosstalk is 0.1%...journal article 2010
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- De Groot, P.C. (author) doctoral thesis 2010
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Van Dijk, T. (author)TU Delft researchers have managed to use a piece of diamond to hold four quantum bits that can be spun, flipped and entangled with each other. This is an important step towards a working quantum computerjournal article 2011
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Van der Sar, T. (author)This thesis describes a series of experiments on the control of the optical properties of the nitrogen-vacancy (NV) center in diamond, and on control of the electron and nuclear spin states associated with the NV center. The NV center is a fluorescing atomic defect center in diamond, consisting of a substitutional nitrogen atom adjacent to a...doctoral thesis 2012
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- Verduijn, J. (author) doctoral thesis 2012
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Braakman, F.R. (author), Barthelemy, P. (author), Reichl, C. (author), Wegscheider, W. (author), Vandersypen, L.M.K. (author)We report both photon- and phonon-assisted tunneling transitions in a linear array of three quantum dots, which can only be understood by considering the full three-dimensionality of the charge stability diagram. Such tunneling transitions potentially contribute to leakage of qubits defined in this system. A detailed understanding of these...journal article 2013