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van Riggelen, F. (author), Lawrie, W.I.L. (author), Russ, M.F. (author), Hendrickx, N.W. (author), Sammak, A. (author), Rispler, M.R.R. (author), Terhal, B.M. (author), Scappucci, G. (author), Veldhorst, M. (author)The fault-tolerant operation of logical qubits is an important requirement for realizing a universal quantum computer. Spin qubits based on quantum dots have great potential to be scaled to large numbers because of their compatibility with standard semiconductor manufacturing. Here, we show that a quantum error correction code can be...journal article 2022
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Petit, L. (author), Russ, M.F. (author), Eenink, H.G.J. (author), Lawrie, W.I.L. (author), Clarke, James S. (author), Vandersypen, L.M.K. (author), Veldhorst, M. (author)Spin qubits in quantum dots define an attractive platform for quantum information because of their compatibility with semiconductor manufacturing, their long coherence times, and the ability to operate above one Kelvin. However, despite demonstrations of SWAP oscillations, the integration of this two-qubit gate together with single-qubit...journal article 2022
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Philips, S.G.J. (author), Madzik, M.T. (author), Amitonov, S. (author), de Snoo, S.L. (author), Russ, M.F. (author), Kalhor, N. (author), Volk, C.A. (author), Lawrie, W.I.L. (author), Brousse, D. (author), Tryputen, L. (author), Paquelet Wuetz, B. (author), Sammak, A. (author), Veldhorst, M. (author), Scappucci, G. (author), Vandersypen, L.M.K. (author)Future quantum computers capable of solving relevant problems will require a large number of qubits that can be operated reliably1. However, the requirements of having a large qubit count and operating with high fidelity are typically conflicting. Spins in semiconductor quantum dots show long-term promise2,3 but demonstrations so far use...journal article 2022
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Lodari, M. (author), Hendrickx, N.W. (author), Lawrie, W.I.L. (author), Hsiao, T. (author), Vandersypen, L.M.K. (author), Sammak, A. (author), Veldhorst, M. (author), Scappucci, G. (author)We engineer planar Ge/SiGe heterostructures for low disorder and quiet hole quantum dot operation by positioning the strained Ge channel 55 nm below the semiconductor/dielectric interface. In heterostructure field effect transistors, we measure a percolation density for two-dimensional hole transport of 2.1 × 10 10 cm−2 , indicative of a very...journal article 2021
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Aggarwal, Kushagra (author), Hofmann, Andrea (author), Jirovec, Daniel (author), Prieto, Ivan (author), Sammak, A. (author), Botifoll, Marc (author), Martí-Sánchez, Sara (author), Veldhorst, M. (author), Scappucci, G. (author)Hole gases in planar germanium can have high mobilities in combination with strong spin-orbit interaction and electrically tunable g factors, and are therefore emerging as a promising platform for creating hybrid superconductor-semiconductor devices. A key challenge towards hybrid Ge-based quantum technologies is the design of high-quality...journal article 2021
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Rossi, Alessandro (author), Hendrickx, N.W. (author), Sammak, A. (author), Veldhorst, M. (author), Scappucci, G. (author), Kataoka, Masaya (author)Single-charge pumps are the main candidates for quantum-based standards of the unit ampere because they can generate accurate and quantized electric currents. In order to approach the metrological requirements in terms of both accuracy and speed of operation, in the past decade there has been a focus on semiconductor-based devices. The use of...journal article 2021
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Liles, S. D. (author), Martins, F. (author), Miserev, D. S. (author), Kiselev, A. (author), Thorvaldson, I. D. (author), Rendell, M. J. (author), Jin, I. K. (author), Hudson, F. E. (author), Veldhorst, M. (author)Single holes confined in semiconductor quantum dots are a promising platform for spin-qubit technology, due to the electrical tunability of the g factor of holes. However, the underlying mechanisms that enable electric spin control remain unclear due to the complexity of hole-spin states. Here, we study the underlying hole-spin physics of the...journal article 2021
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Xue, X. (author), Patra, B (author), van Dijk, J.P.G. (author), Samkharadze, Nodar (author), Corna, A. (author), Paquelet Wuetz, B. (author), Sammak, A. (author), Scappucci, G. (author), Veldhorst, M. (author), Sebastiano, F. (author), Babaie, M. (author), Charbon-Iwasaki-Charbon, E. (author), Vandersypen, L.M.K. (author)The most promising quantum algorithms require quantum processors that host millions of quantum bits when targeting practical applications<sup>1</sup>. A key challenge towards large-scale quantum computation is the interconnect complexity. In current solid-state qubit implementations, an important interconnect bottleneck appears between the...journal article 2021
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van Riggelen, F. (author), Hendrickx, N.W. (author), Lawrie, W.I.L. (author), Russ, M.F. (author), Sammak, A. (author), Scappucci, G. (author), Veldhorst, M. (author)Quantum dots fabricated using methods compatible with semiconductor manufacturing are promising for quantum information processing. In order to fully utilize the potential of this platform, scaling quantum dot arrays along two dimensions is a key step. Here, we demonstrate a two-dimensional quantum dot array where each quantum dot is tuned to...journal article 2021
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Hendrickx, N.W. (author), Lawrie, W.I.L. (author), Petit, L. (author), Sammak, A. (author), Scappucci, G. (author), Veldhorst, M. (author)Qubits based on quantum dots have excellent prospects for scalable quantum technology due to their compatibility with standard semiconductor manufacturing. While early research focused on the simpler electron system, recent demonstrations using multi-hole quantum dots illustrated the favourable properties holes can offer for fast and scalable...journal article 2020
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Paquelet Wuetz, B. (author), Bavdaz, P.L. (author), Yeoh, L.A. (author), Schouten, R.N. (author), van der Does, C.H. (author), Tiggelman, M.J. (author), Sabbagh, D. (author), Sammak, A. (author), Almudever, Carmen G. (author), Sebastiano, F. (author), Clarke, J. S. (author), Veldhorst, M. (author), Scappucci, G. (author)Continuing advancements in quantum information processing have caused a paradigm shift from research mainly focused on testing the reality of quantum mechanics to engineering qubit devices with numbers required for practical quantum computation. One of the major challenges in scaling toward large-scale solid-state systems is the limited input...journal article 2020
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XU, Y. (author), Unseld, F.K. (author), Corna, A. (author), Zwerver, A.M.J. (author), Sammak, A. (author), Brousse, D. (author), Samkharadze, Nodar (author), Amitonov, S. (author), Veldhorst, M. (author), Scappucci, G. (author), Ishihara, R. (author), Vandersypen, L.M.K. (author)Solid-state qubits integrated on semiconductor substrates currently require at least one wire from every qubit to the control electronics, leading to a so-called wiring bottleneck for scaling. Demultiplexing via on-chip circuitry offers an effective strategy to overcome this bottleneck. In the case of gate-defined quantum dot arrays, specific...journal article 2020
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Lawrie, W.I.L. (author), Hendrickx, N.W. (author), van Riggelen, F. (author), Russ, M.F. (author), Petit, L. (author), Sammak, A. (author), Scappucci, G. (author), Veldhorst, M. (author)We investigate hole spin relaxation in the single- and multihole regime in a 2 × 2 germanium quantum dot array. We find spin relaxation times T1 as high as 32 and 1.2 ms for quantum dots with single- and five-hole occupations, respectively, setting benchmarks for spin relaxation times for hole quantum dots. Furthermore, we investigate qubit...journal article 2020
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Van DIjk, Jeroen Petrus Gerardus (author), Patra, B (author), Xue, X. (author), Samkharadze, Nodar (author), Corna, A. (author), Sammak, A. (author), Scappucci, G. (author), Veldhorst, M. (author), Vandersypen, L.M.K. (author), Charbon-Iwasaki-Charbon, E. (author), Babaie, M. (author), Sebastiano, F. (author)Building a large-scale quantum computer requires the co-optimization of both the quantum bits (qubits) and their control electronics. By operating the CMOS control circuits at cryogenic temperatures (cryo-CMOS), and hence in close proximity to the cryogenic solid-state qubits, a compact quantum-computing system can be achieved, thus promising...journal article 2020
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Paquelet Wuetz, B. (author), Losert, Merritt P. (author), Tosato, A. (author), Lodari, M. (author), Bavdaz, P.L. (author), Stehouwer, Lucas (author), Sammak, A. (author), Veldhorst, M. (author), Scappucci, G. (author)We determine the energy splitting of the conduction-band valleys in two-dimensional electrons confined to low-disorder Si quantum wells. We probe the valley splitting dependence on both perpendicular magnetic field B and Hall density by performing activation energy measurements in the quantum Hall regime over a large range of filling factors....journal article 2020
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Franke, D.P. (author), Clarke, J. S. (author), Vandersypen, L.M.K. (author), Veldhorst, M. (author)Quantum computing is on the verge of a transition from fundamental research to practical applications. Yet, to make the step to large-scale quantum computation, an extensible qubit system has to be developed. In classical semiconductor technology, this was made possible by the invention of the integrated circuit, which allowed to interconnect...journal article 2019
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Hendrickx, N.W. (author), Tagliaferri, M.L.V. (author), Kouwenhoven, M. (author), Li, R. (author), Franke, D.P. (author), Sammak, A. (author), Brinkman, A. (author), Scappucci, G. (author), Veldhorst, M. (author)We fabricate Josephson field-effect transistors in germanium quantum wells contacted by superconducting aluminum and demonstrate supercurrents carried by holes that extend over junction lengths of several micrometers. In superconducting quantum point contacts we observe discretization of supercurrent, as well as Fabry-Pérot resonances,...journal article 2019
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Lodari, M. (author), Tosato, A. (author), Sabbagh, D. (author), Schubert, M. A. (author), Capellini, G. (author), Sammak, A. (author), Veldhorst, M. (author), Scappucci, G. (author)We report density-dependent effective hole mass measurements in undoped germanium quantum wells. We are able to span a large range of densities (2.0-11×1011cm-2) in top-gated field effect transistors by positioning the strained buried Ge channel at different depths of 12 and 44 nm from the surface. From the thermal damping of the amplitude of...journal article 2019
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Sammak, A. (author), Sabbagh, D. (author), Hendrickx, N.W. (author), Lodari, M. (author), Paquelet Wuetz, Brian (author), Tosato, A. (author), Yeoh, L.A. (author), Veldhorst, M. (author), Scappucci, G. (author)Buried-channel semiconductor heterostructures are an archetype material platform for the fabrication of gated semiconductor quantum devices. Sharp confinement potential is obtained by positioning the channel near the surface; however, nearby surface states degrade the electrical properties of the starting material. Here, a 2D hole gas of high...journal article 2019
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van Dijk, J.P.G. (author), Kawakami, E. (author), Schouten, R.N. (author), Veldhorst, M. (author), Vandersypen, L.M.K. (author), Babaie, M. (author), Charbon-Iwasaki-Charbon, E. (author), Sebastiano, F. (author)Quantum processors rely on classical electronic controllers to manipulate and read out the state of quantum bits (qubits). As the performance of the quantum processor improves, nonidealities in the classical controller can become the performance bottleneck for the whole quantum computer. To prevent such limitation, this paper presents a...journal article 2019