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Full parity phase diagram of a proximitized nanowire island

Physical Review B 2021年第4期104卷 045422-045422页

作者： J. Shen G. W. Winkler F. Borsoi S. Heedt V. Levajac J.-Y. Wang D. van Driel D. Bouman S. Gazibegovic R. L. M. Op Het Veld D. Car J. A. Logan M. Pendharkar C. J. Palmstrøm E. P. A. M. Bakkers L. P. Kouwenhoven B. van Heck QuTech and Kavli Institute of Nanoscience Delft University of Technology 2600 GA Delft The Netherlands Beijing National Laboratory for Condensed Matter Physics Institute of Physics Chinese Academy of Sciences Beijing 100190 China Microsoft Quantum Microsoft Station Q University of California Santa Barbara Santa Barbara California 93106 USA Microsoft Quantum Lab Delft 2600 GA Delft The Netherlands Department of Applied Physics Eindhoven University of Technology 5600 MB Eindhoven The Netherlands Materials Department University of California Santa Barbara Santa Barbara California 93106 USA Electrical and Computer Engineering University of California Santa Barbara Santa Barbara California 93106 USA

We measure the charge periodicity of Coulomb blockade conductance oscillations of a hybrid InSb-Al island as a function of gate voltage and parallel magnetic field. The periodicity changes from 2e to 1e at a gate-dependent value of the magnetic field, B*, decreasing from a high to a low limit upon increasing the gate voltage. In the gate voltage region between the two limits, which our numerical simulations indicate to be the most promising for locating Majorana zero modes, we observe correlated oscillations of peak spacings and heights. For positive gate voltages, the 2e−1e transition with low B* is due to the presence of nontopological states whose energy quickly disperses below the charging energy due to the orbital effect of the magnetic field. Our measurements highlight the importance of a careful exploration of the entire available phase space of a proximitized nanowire as a prerequisite to define future topological qubits.

关键词： Majorana bound states Mesoscopics Proximity effect Nanowires Superconducting devices

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RETRACTION: Epitaxy of advanced nanowire quantum devices (Retraction of Vol 548, Pg 434, 2017)

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NATURE 2022年第7907期604卷 786-786页

作者： Gazibegovic, Sasa Car, Diana Zhang, Hao Balk, Stijn C. Logan, John A. de Moor, Michiel W. A. Cassidy, Maja C. Schmits, Rudi Xu, Di Wang, Guanzhong Krogstrup, Peter Op Het Veld, Roy L. M. Zuo, Kun Vos, Yoram Shen, Jie Bouman, Daniel Shojaei, Borzoyeh Pennachio, Daniel Lee, Joon Sue van Veldhoven, Petrus J. Koelling, Sebastian Verheijen, Marcel A. Kouwenhoven, Leo P. Palmstrom, Chris J. Bakkers, Erik P. A. M. QuTech and Kavli Institute of NanoScience Delft University of Technology Delft The Netherlands Department of Applied Physics Eindhoven University of Technology Eindhoven The Netherlands Microsoft Station-Q at Delft University of Technology Delft The Netherlands Philips Innovation Services Eindhoven High Tech Campus 11 Eindhoven The Netherlands Materials Department University of California Santa Barbara California USA California NanoSystems Institute University of California Santa Barbara California USA Electrical and Computer Engineering University of California Santa Barbara California USA TNO Technical Sciences Nano-Instrumentation Department Delft The Netherlands Center for Quantum Devices and Station-Q Copenhagen Niels Bohr Institute University of Copenhagen Copenhagen Denmark

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Lindblad Tomography of a Superconducting quantum Processor

arXiv

引用

arXiv 2021年

作者： Samach, Gabriel O. Greene, Ami Borregaard, Johannes Christandl, Matthias Barreto, Joseph Kim, David K. McNally, Christopher M. Melville, Alexander Niedzielski, Bethany M. Sung, Youngkyu Rosenberg, Danna Schwartz, Mollie E. Yoder, Jonilyn L. Orlando, Terry P. Wang, Joel I-Jan Gustavsson, Simon Kjaergaard, Morten Oliver, William D. Research Laboratory of Electronics Massachusetts Institute of Technology CambridgeMA02139 United States MIT Lincoln Laboratory LexingtonMA02421 United States Qutech and Kavli Institute of Nanoscience Delft University of Technology Delft Netherlands Department of Mathematical Sciences University of Copenhagen Copenhagen Denmark Center for Quantum Devices Niels Bohr Institute University of Copenhagen Copenhagen Denmark Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology CambridgeMA02139 United States

As progress is made towards the first generation of error-corrected quantum computers, robust characterization and validation protocols are required to assess the noise environments of physical quantum processors. While standard coherence metrics and characterization protocols such as T1 and T2, process tomography, and randomized benchmarking are now ubiquitous, these techniques provide only partial information about the dynamic multi-qubit loss channels responsible for processor errors, which can be described more fully by a Lindblad operator in the master equation formalism. Here, we introduce and experimentally demonstrate Lindblad tomography, a hardware-agnostic characterization protocol for tomographically reconstructing the Hamiltonian and Lindblad operators of a quantum noise environment from an ensemble of time-domain measurements. Performing Lindblad tomography on a small superconducting quantum processor, we show that this technique naturally builds on standard process tomography and T1/T2 measurement protocols, characterizes and accounts for state-preparation and measurement (SPAM) errors, and allows one to place bounds on the fit to a Markovian model Comparing the results of single- and two-qubit measurements on a superconducting quantum processor, we demonstrate that Lindblad tomography can also be used to identify and quantify sources of crosstalk on quantum processors, such as the presence of always-on qubit-qubit interactions. Copyright © 2021, The Authors. All rights reserved.

关键词： Tomography

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Data Needs and Challenges for quantum Dot Devices Automation

arXiv

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arXiv 2023年

作者： Zwolak, Justyna P. Taylor, Jacob M. Andrews, Reed Benson, Jared Bryant, Garnett Buterakos, Donovan Chatterjee, Anasua Sarma, Sankar Das Eriksson, Mark A. Greplová, Eliška Gullans, Michael J. Hader, Fabian Kovach, Tyler J. Mundada, Pranav S. Ramsey, Mick Rasmussen, Torbjoern Severin, Brandon Sigillito, Anthony Undseth, Brennan Weber, Brian National Institute of Standards and Technology GaithersburgMD20899 United States Joint Center for Quantum Information and Computer Science University of Maryland College ParkMD20742 United States Department of Physics University of Maryland College ParkMD20742 United States Joint Quantum Institute National Institute of Standards and Technology University of Maryland GaithersburgMD20899 United States HRL Laboratories LLC 3011 Malibu Canyon Road MalibuCA90265 United States Department of Physics University of Wisconsin-Madison MadisonWI53706 United States Center for Quantum Devices Niels Bohr Institute University of Copenhagen Copenhagen2100 Denmark Condensed Matter Theory Center University of Maryland College ParkMD20742 United States Kavli Institute of Nanoscience Delft University of Technology Lorentzweg 1 Delft2628 CJ Netherlands Central Institute of Engineering Electronics and Analytics ZEA-2 - Electronic Systems Forschungszentrum Jülich GmbH Jülich52425 Germany Q-CTRL Santa MonicaCA90401 United States Intel Components Research Intel Corporation HillsboroOR97124 United States Department of Materials University of Oxford Parks Road OxfordOX1 3PH United Kingdom School of Electrical Engineering and Telecommunications The University of New South Wales SydneyNSW2052 Australia Department of Electrical and Systems Engineering University of Pennsylvania PhiladelphiaPA19104 United States QuTech Delft University of Technology Lorentzweg 1 Delft2628 CJ Netherlands Intelligent Geometries LLC Lake Frederick VA22630 United States

Gate-defined quantum dots are a promising candidate system for realizing scalable, coupled qubit systems and serving as a fundamental building block for quantum computers. However, presentday quantum dot devices suffer from imperfections that must be accounted for, which hinders the characterization, tuning, and operation process. Moreover, with an increasing number of quantum dot qubits, the relevant parameter space grows sufficiently to make heuristic control infeasible. Thus, it is imperative that reliable and scalable autonomous tuning approaches are developed. This meeting report outlines current challenges in automating quantum dot device tuning and operation with a particular focus on datasets, benchmarking, and standardization. We also present insights and ideas put forward by the quantum dot community on how to overcome them. We aim to provide guidance and inspiration to researchers invested in automation efforts. Copyright © 2023, The Authors. All rights reserved.

关键词： Nanocrystals

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Large zero-bias peaks in InSb-Al hybrid semiconductor-superconductor nanowire devices

arXiv

引用

arXiv 2021年

作者： Zhang, Hao de Moor, Michiel W.A. Bommer, Jouri D.S. Xu, Di Wang, Guanzhong van Loo, Nick Liu, Chun-Xiao Gazibegovic, Sasa Logan, John A. Car, Diana Op het Veld, Roy L.M. van Veldhoven, Petrus J. Koelling, Sebastian Verheijen, Marcel A. Pendharkar, Mihir Pennachio, Daniel J. Shojaei, Borzoyeh Lee, Joon Sue Palmstrøm, Chris J. Bakkers, Erik P.A.M. Das Sarma, S. Kouwenhoven, Leo P. QuTech Delft University of Technology Delft2600 GA Netherlands Kavli Institute of Nanoscience Delft University of Technology Delft2600 GA Netherlands State Key Laboratory of Low Dimensional Quantum Physics Department of Physics Tsinghua University Beijing100084 China Condensed Matter Theory Center Joint Quantum Institute Department of Physics University of Maryland College ParkMD20742 United States Department of Applied Physics Eindhoven University of Technology Eindhoven5600 MB Netherlands Materials Engineering University of California Santa Barbara CA93106 United States Electrical and Computer Engineering University of California Santa Barbara Santa BarbaraCA93106 United States California NanoSystems Institute University of California Santa Barbara Santa BarbaraCA93106 United States Microsoft Quantum Lab Delft Delft2600 GA Netherlands

We report electron transport studies on InSb-Al hybrid semiconductor-superconductor nanowire devices. Tunnelling spectroscopy is used to measure the evolution of subgap states while varying magnetic field and voltages applied to various nearby gates. At magnetic fields between 0.7 and 0.9 T, the differential conductance contains large zero bias peaks (ZBPs) whose height reaches values on the order 2e2/h. We investigate these ZBPs for large ranges of gate voltages in different devices. We discuss possible interpretations in terms of disorder-induced subgap states, Andreev bound states and Majorana zero modes. © 2021, CC BY.

关键词： Indium antimonides

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quantum Dots in an InSb Two-Dimensional Electron Gas

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Physical Review Applied 2020年第4期13卷 041003-041003页

作者： Ivan Kulesh Chung Ting Ke Candice Thomas Saurabh Karwal Christian M. Moehle Sara Metti Ray Kallaher Geoffrey C. Gardner Michael J. Manfra Srijit Goswami QuTech and Kavli Institute of Nanoscience Delft University of Technology 2600 GA Delft Netherlands Department of Physics and Astronomy Purdue University West Lafayette Indiana 47907 USA Birck Nanotechnology Center Purdue University West Lafayette Indiana 47907 USA QuTech and Netherlands Organization for Applied Scientific Research (TNO) 2628 CK Delft Netherlands School of Electrical and Computer Engineering Purdue University West Lafayette Indiana 47907 USA Microsoft Quantum Purdue Purdue University West Lafayette Indiana 47907 USA School of Materials Engineering Purdue University West Lafayette Indiana 47907 USA

Indium-antimonide (InSb) two-dimensional electron gases (2DEGs) have a unique combination of material properties: high electron mobility, a strong spin-orbit interaction, a large Landé g factor, and a small effective mass. This makes them an attractive platform to explore a variety of mesoscopic phenomena ranging from spintronics to topological superconductivity. However, there exist limited studies of quantum confined systems in these 2DEGs, often attributed to charge instabilities and gate drifts. We overcome this by removing the δ-doping layer from the heterostructure and induce carriers electrostatically. This allows us to perform a detailed study of stable gate-defined quantum dots in InSb 2DEGs. We demonstrate two distinct strategies for carrier confinement and study the charge stability of the dots. The small effective mass results in a relatively large single-particle spacing, allowing for the observation of an even-odd variation in the addition energy. By tracking the Coulomb oscillations in a parallel magnetic field, we determine the ground-state spin configuration and show that the large g factor (approximately 30) results in a singlet-triplet transition at magnetic fields as low as 0.3 T.

关键词： Mesoscopics quantum information with solid state qubits Spin-orbit coupling Spintronics III-V semiconductors quantum dots Topological materials Two-dimensional electron gas

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InSbAs two-dimensional electron gases as a platform for topological superconductivity

arXiv

引用

arXiv 2021年

作者： Moehle, Christian M. Ke, Chung Ting Wang, Qingzhen Thomas, Candice Xiao, Di Karwal, Saurabh Lodari, Mario van de Kerkhof, Vincent Termaat, Ruben Gardner, Geoffrey C. Scappucci, Giordano Manfra, Michael J. Goswami, Srijit QuTech and Kavli Institute of Nanoscience Delft University of Technology Delft2600 GA Netherlands Department of Physics and Astronomy Purdue University West LafayetteIN47907 United States Birck Nanotechnology Center Purdue University West LafayetteIN47907 United States Delft2628 CK Netherlands Microsoft Quantum Purdue Purdue University West LafayetteIN47907 United States School of Electrical and Computer Engineering Purdue University West LafayetteIN47907 United States School of Materials Engineering Purdue University West LafayetteIN47907 United States

Topological superconductivity can be engineered in semiconductors with strong spin-orbit interaction coupled to a superconductor. Experimental advances in this field have often been triggered by the development of new hybrid material systems. Among these, two-dimensional electron gases (2DEGs) are of particular interest due to their inherent design flexibility and scalability. Here we discuss results on a 2D platform based on a ternary 2DEG (InSbAs) coupled to in-situ grown Aluminum. The spin-orbit coupling in these 2DEGs can be tuned with the As concentration, reaching values up to 400 meVÅ, thus exceeding typical values measured in its binary constituents. In addition to a large Landé g-factor ∼ 55 (comparable to InSb), we show that the clean superconductor-semiconductor interface leads to a hard induced superconducting gap. Using this new platform we demonstrate the basic operation of phase-controllable Josephson junctions, superconducting islands and quasi-1D systems, prototypical device geometries used to study Majorana zero modes. © 2021, CC BY.

关键词： III-V semiconductors

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Timing and resource-aware mapping of quantum circuits to superconducting processors

arXiv

引用

arXiv 2019年

作者： Lao, Lingling van Someren, Hans Ashraf, Imran Almudever, Carmen G. QuTech Delft University of Technology Netherlands Department of Quantum and Computer Engineering Delft University of Technology Netherlands Department of Physics and Astronomy University College London United Kingdom

quantum algorithms need to be compiled to respect the constraints imposed by quantum processors, which is known as the mapping problem. The mapping procedure will result in an increase of the number of gates and of the circuit latency, decreasing the algorithm's success rate. It is crucial to minimize mapping overhead, especially for Noisy Intermediate-Scale quantum (NISQ) processors that have relatively short qubit coherence times and high gate error rates. Most of prior mapping algorithms have only considered constraints such as the primitive gate set and qubit connectivity, but the actual gate duration and the restrictions imposed by the use of shared classical control electronics have not been taken into account. In this paper, we present a timing and resource-aware mapper called Qmap to make quantum circuits executable on a scalable superconducting processor named Surface-17 with the objective of achieving the shortest circuit latency. In particular, we propose an approach to formulate the classical control restrictions as resource constraints in a conventional list scheduler with polynomial complexity. Furthermore, we implement a routing heuristic to cope with the connectivity limitation. This router finds a set of movement operations that minimally extends circuit latency. To analyze the mapping overhead and evaluate the performance of different mappers, we map 56 quantum benchmarks onto Surface-17. Compared to a prior mapping strategy that minimizes the number of operations, Qmap can reduce the latency overhead up to 47.3% and operation overhead up to 28.6%, respectively. Copyright © 2019, The Authors. All rights reserved.

关键词： Timing circuits

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Spiderweb array: A sparse spin-qubit array

arXiv

引用

arXiv 2021年

作者： Boter, Jelmer M. Dehollain, Juan Pablo van Dijk, Jeroen P.G. Xu, Yuanxing Hensgens, Toivo Versluis, Richard Naus, Henricus W.L. Clarke, James S. Veldhorst, Menno Sebastiano, Fabio Vandersypen, Lieven M.K. QuTech Delft University of Technology Lorentzweg 1 Delft2628 CJ Netherlands Kavli Institute of Nanoscience Delft University of Technology Lorentzweg 1 Delft2628 CJ Netherlands School of Mathematical and Physical Sciences University of Technology Sydney UltimoNSW2007 Australia Department of Quantum and Computer Engineering Delft University of Technology Delft2628 CJ Netherlands P.O. Box 155 Delft2600 AD Netherlands Components Research Intel Corporation 2501 NE Century Blvd HillsboroOR97124 United States

One of the main bottlenecks in the pursuit of a large-scale–chip-based quantum computer is the large number of control signals needed to operate qubit systems. As system sizes scale up, the number of terminals required to connect to off-chip control electronics quickly becomes unmanageable. Here, we discuss a quantum-dot spin-qubit architecture that integrates on-chip control electronics, allowing for a significant reduction in the number of signal connections at the chip boundary. By arranging the qubits in a two-dimensional (2D) array with ∼12 µm pitch, we create space to implement locally integrated sample-and-hold circuits. This allows to offset the inhomogeneities in the potential landscape across the array and to globally share the majority of the control signals for qubit operations. We make use of advanced circuit modeling software to go beyond conceptual drawings of the component layout, to assess the feasibility of the scheme through a concrete floor plan, including estimates of footprints for quantum and classical electronics, as well as routing of signal lines across the chip using different interconnect layers. We make use of local demultiplexing circuits to achieve an efficient signal-connection scaling leading to a Rent’s exponent as low as p = 0.43. Furthermore, we use available data from state-of-the-art spin qubit and microelectronics technology development, as well as circuit models and simulations, to estimate the operation frequencies and power consumption of a million-qubit array. This work presents a complementary approach to previously proposed architectures, focusing on a feasible scheme to integrating quantum and classical hardware, and identifying remaining challenges for achieving full fault-tolerant quantum computation. It thereby significantly closes the gap towards a fully CMOS-compatible quantum computer implementation. © 2021, CC BY.

关键词： Qubits

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Conformal Properties of Hyperinvariant Tensor Networks

arXiv

引用

arXiv 2020年

作者： Steinberg, Matthew Prior, Javier QuTech Delft University of Technology Delft Netherlands Quantum and Computer Engineering Department Delft University of Technology Delft Netherlands Departamento de Física Aplicada Universidad Politécnica de Cartagena Cartagena30202 Spain Instituto Carlos I de Física Teórica y Computacional Universidad de Granada Granada18071 Spain

Hyperinvariant tensor networks (hyMERA) were introduced as a way to combine the successes of perfect tensor networks (HaPPY) and the multiscale entanglement renormalization ansatz (MERA) in simulations of the AdS/CFT correspondence. Although this new class of tensor network shows much potential for simulating conformal field theories arising from hyperbolic bulk manifolds with quasiperiodic boundaries, many issues are unresolved. In this manuscript we analyze the challenges related to optimizing tensors in a hyMERA with respect to some quasiperiodic critical spin chain, and compare with standard approaches in MERA. Additionally, we show two new sets of tensor decompositions which exhibit different properties from the original construction, implying that the multitensor constraints are neither unique, nor difficult to find, and that a generalization of the analytical tensor forms used up until now may exist. Lastly, we perform randomized trials using a descending superoperator with several of the investigated tensor decompositions, and find that the constraints imposed on the spectra of local descending superoperators in hyMERA are compatible with the operator spectra of several minimial model CFTs. Copyright © 2020, The Authors. All rights reserved.

关键词： Tensors

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