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arXiv 2023年

作者： Battistel, Francesco Chamberland, Christopher Johar, Kauser Overwater, Ramon W.J. Sebastiano, Fabio Skoric, Luka Ueno, Yosuke Usman, Muhammad Qblox Elektronicaweg 10 Delft2628 XG Netherlands AWS Center for Quantum Computing PasadenaCA91125 United States IQIM California Institute of Technology PasadenaCA91125 United States Riverlane Ltd Cambridge United Kingdom QuTech Department of Quantum and Computer Engineering Delft University of Technology Delft2600 GA Netherlands Graduate School of Information Science and Technology The University of Tokyo Tokyo Japan Department of Computer Engineering Technical University of Munich Garching Germany School of Physics The University of Melbourne Parkville3010 Australia Data61 CSIRO Clayton3168 Australia

quantum computing is poised to solve practically useful problems which are computationally intractable for classical supercomputers. However, the current generation of quantum computers are limited by errors that may only partially be mitigated by developing higher-quality qubits. quantum error correction (QEC) will thus be necessary to ensure fault tolerance. QEC protects the logical information by cyclically measuring syndrome information about the errors. An essential part of QEC is the decoder, which uses the syndrome to compute the likely effect of the errors on the logical degrees of freedom and provide a tentative correction. The decoder must be accurate, fast enough to keep pace with the QEC cycle (e.g., on a microsecond timescale for superconducting qubits) and with hard real-time system integration to support logical operations. As such, real-time decoding is essential to realize fault-tolerant quantum computing and to achieve quantum advantage. In this work, we highlight some of the key challenges facing the implementation of real-time decoders while providing a succinct summary of the progress to-date. Furthermore, we lay out our perspective for the future development and provide a possible roadmap for the field of real-time decoding in the next few years. As the quantum hardware is anticipated to scale up, this perspective article will provide a guidance for researchers, focusing on the most pressing issues in real-time decoding and facilitating the development of solutions across quantum and computer science. Copyright © 2023, The Authors. All rights reserved.

关键词： Fault tolerance

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Characterization and modeling of self-heating in nanometer Bulk-CMOS at cryogenic temperatures

arXiv

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arXiv 2021年

作者： t'Hart, P.A. Babaie, M. Vladimirescu, A. Sebastiano, F. QuTech Delft University of Technology Netherlands Department of Quantum and Computer Engineering Delft University of Technology Netherlands ISEP Paris France UC Berkeley BerkeleyCA United States

This work presents a self-heating study of a 40-nm bulk-CMOS technology in the ambient temperature range from 300 K down to 4.2 K. A custom test chip was designed and fabricated for measuring both the temperature rise in the MOSFET channel and in the surrounding silicon substrate, using the gate resistance and silicon diodes as sensors, respectively. Since self-heating depends on factors such as device geometry and power density, the test structure characterized in this work was specifically designed to resemble actual devices used in cryogenic qubit control ICs. Severe self-heating was observed at deep-cryogenic ambient temperatures, resulting in a channel temperature rise exceeding 50 K and having an impact detectable at a distance of up to 30 µm from the device. By extracting the thermal resistance from measured data at different temperatures, it was shown that a simple model is able to accurately predict channel temperatures over the full ambient temperature range from deep-cryogenic to room temperature. The results and modeling presented in this work contribute towards the full self-heating-aware IC design-flow required for the reliable design and operation of cryo-CMOS circuits. Copyright © 2021, The Authors. All rights reserved.

关键词： Cryogenics

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Strain effects in a directly bonded diamond-on-insulator substrate

arXiv

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arXiv 2025年

作者： Varveris, Ioannis Aliberti, Gianni D. Chen, Tianyin Sfetcu, Filip A. Dekker, Diederik J.W. Schuurmans, Alfred Nitzsche, Nikolaj K. Nur, Salahuddin Ishihara, Ryoichi QuTech Delft University of Technology Lorentzweg 1 Delft2628 CJ Netherlands Department of Quantum & Computer Engineering Delft University of Technology Mekelweg 4 Delft2628 CD Netherlands

The direct bonding process of a diamond-on-insulator (DOI) substrate enables monolithic integration of diamond photonic structures for quantum computing by improving photon collection efficiency and entanglement generation rate between emitters. It also addresses key fabrication challenges, such as robustness, bonding strength, and scalability. In this study, we investigate strain effects in DOI substrates following direct bonding. Strain generation is expected near the diamond-SiO2/Si interface due to thermal expansion coefficient mismatch between the bonded materials. Strain-induced lattice distortions are characterized using nitrogen-vacancy (NV) centers in diamond via optically detected magnetic resonance (ODMR) and photoluminescence (PL) mapping. PL mapping reveals interference fringes in unbonded regions, indicating bonding irregularities. Depth-resolved ODMR measurements show a volumetric strain component increase of ∼0.45 MHz and a shear component increase of ∼0.71 MHz between the top surface and the DOI interface. However, ODMR signal contrast and peak linewidth remain largely unaffected, suggesting no visible deterioration in the optical properties of the emitters. By combining ODMR and PL mapping, this work establishes a robust methodology for assessing bonding quality and strain impact on NV centers, an essential step toward advancing scalable quantum technologies and integrated photonic circuits. © 2025, CC BY-NC-ND.

关键词： Qubits

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Modelling of planar germanium hole qubits in electric and magnetic fields

arXiv

引用

arXiv 2022年

作者： Wang, Chien-An Ercan, H. Ekmel Gyure, Mark F. Scappucci, Giordano Veldhorst, Menno Rimbach-Russ, Maximilian QuTech and Kavli Institute of Nanoscience Delft University of Technology PO Box 5046 Delft2600 GA Netherlands Electrical and Computer Engineering Department University of California Los AngelesCA90095 United States Center for Quantum Science and Engineering University of California Los AngelesCA90095 United States

Hole-based spin qubits in strained planar germanium quantum wells have received considerable attention due to their favourable properties and remarkable experimental progress. The sizeable spin-orbit interaction in this structure allows for efficient qubit operations with electric fields. However, it also couples the qubit to electrical noise. In this work, we perform simulations of a heterostructure hosting these hole spin qubits. We solve the effective mass equations for a realistic heterostructure, provide a set of analytical basis wave functions, and compute the effective g-factor of the heavy-hole ground-state. Our investigations reveal a strong impact of highly excited light-hole states located outside the quantum well on the g-factor. We find that sweet spots, points of operations that are least susceptible to charge noise, for out-of-plane magnetic fields are shifted to impractically large electric fields. However, for magnetic fields close to in-plane alignment, partial sweet spots at low electric fields are recovered. Furthermore, sweet spots with respect to multiple fluctuating charge traps can be found under certain circumstances for different magnetic field alignments. This work will be helpful in understanding and improving coherence of germanium hole spin qubits. Copyright © 2022, The Authors. All rights reserved.

关键词： Qubits

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Automated in situ optimization and disorder mitigation in a quantum device

arXiv

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arXiv 2024年

作者： Benestad, Jacob Rasmussen, Torbjorn Brovang, Bertram Krause, Oswin Fallahi, Saeed Gardner, Geoffrey C. Manfra, Michael J. Marcus, Charles M. Danon, Jeroen Kuemmeth, Ferdinand Chatterjee, Anasua van Nieuwenburg, Evert Center for Quantum Spintronics Department of Physics Norwegian University of Science and Technology TrondheimNO-7491 Norway Center for Quantum Devices Niels Bohr Institute University of Copenhagen Copenhagen2100 Denmark QuTech and Kavli Institute of Nanoscience Delft University of Technology Delft2600 GA Netherlands Department of Computer Science University of Copenhagen Copenhagen2100 Denmark Department of Physics and Astronomy Purdue University West LafayetteIN47907 United States Birck Nanotechnology Center Purdue University West LafayetteIN47907 United States Elmore Family School of Electrical and Computer Engineering Purdue University West LafayetteIN47907 United States School of Materials Engineering Purdue University West LafayetteIN47907 United States aQaL Lorentz Institute Leiden Institute of Advanced Computer Science Leiden University P.O. Box 9506 Leiden2300 RA Netherlands

We investigate automated in situ optimization of the potential landscape in a quantum point contact device, using a 3×3 gate array patterned atop the constriction. Optimization is performed using the covariance matrix adaptation evolutionary strategy, for which we introduce a metric for how "step-like" the conductance is as the channel becomes constricted. We first perform the optimization of the gate voltages in a tight-binding simulation and show how such in situ tuning can be used to mitigate a random disorder potential. The optimization is then performed in a physical device in experiment, where we also observe a marked improvement in the quantization of the conductance resulting from the optimization procedure. © 2024, CC BY.

关键词： Covariance matrix

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quantum repeaters: From quantum networks to the quantum internet

引用

Reviews of Modern Physics 2023年第4期95卷 045006-045006页

作者： Koji Azuma Sophia E. Economou David Elkouss Paul Hilaire Liang Jiang Hoi-Kwong Lo Ilan Tzitrin NTT Basic Research Laboratories NTT Corporation 3-1 Morinosato-Wakamiya Atsugi Kanagawa 243-0198 Japan and NTT Research Center for Theoretical Quantum Information NTT Corporation 3-1 Morinosato-Wakamiya Atsugi Kanagawa 243-0198 Japan Department of Physics Virginia Tech Blacksburg Virginia 24061 USA QuTech Delft University of Technology Lorentzweg 1 2628 CJ Delft The Netherlands and Networked Quantum Devices Unit Okinawa Institute of Science and Technology Graduate University Okinawa Japan Department of Physics Virginia Tech Blacksburg Virginia 24061 USA and Quandela SAS 10 Boulevard Thomas Gobert 91120 Palaiseau France Pritzker School of Molecular Engineering The University of Chicago Chicago Illinois 60637 USA Quantum Bridge Technologies Inc. 100 College Street Toronto Ontario M5G 1L5 Canada Department of Physics University of Hong Kong Pokfulam Hong Kong and Center for Quantum Information and Quantum Control Department of Physics and Department of Electrical and Computer Engineering University of Toronto Toronto Ontario M5S 3G4 Canada Department of Physics University of Toronto Toronto Ontario Canada

A quantum internet is the holy grail of quantum information processing, enabling the deployment of a broad range of quantum technologies and protocols on a global scale. However, numerous challenges must be addressed before the quantum internet can become a reality. Perhaps the most crucial of these is the realization of a quantum repeater, an essential component in the long-distance transmission of quantum information. As the analog of a classical repeater, extender, or booster, the quantum repeater works to overcome loss and noise in the quantum channels constituting a quantum network. Here the conceptual frameworks and architectures for quantum repeaters, as well as the experimental progress toward their realization, are reviewed. Various near-term proposals to overcome the limits to the communication rates set by point-to-point quantum communication are also discussed. Finally, the manner in which quantum repeaters fit within the broader challenge of designing and implementing a quantum internet is overviewed.

关键词： quantum communication quantum memories quantum networks quantum repeaters Internet

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Electrical operation of planar Ge hole spin qubits in an in-plane magnetic field

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Physical Review B 2023年第24期108卷 245301-245301页

作者： Abhikbrata Sarkar Zhanning Wang Matthew Rendell Nico W. Hendrickx Menno Veldhorst Giordano Scappucci Mohammad Khalifa Joe Salfi Andre Saraiva A. S. Dzurak A. R. Hamilton Dimitrie Culcer School of Physics The University of New South Wales Sydney 2052 Australia QuTech and Kavli Institute of Nanoscience Delft University of Technology 2628 CJ Delft The Netherlands Department of Electrical and Computer Engineering University of British Columbia Vancouver B.C. V6T 1Z4 Canada Quantum Matter Institute University of British Columbia Vancouver B.C. V6T 1Z4 Canada School of Electrical Engineering and Telecommunications The University of New South Wales Sydney 2052 Australia

Hole spin qubits in group-IV semiconductors, especially Ge and Si, are actively investigated as platforms for ultrafast electrical spin manipulation thanks to their strong spin-orbit coupling. Nevertheless, the theoretical understanding of spin dynamics in these systems is in the early stages of development, particularly for in-plane magnetic fields as used in the vast majority of experiments. In this work, we present a comprehensive theory of spin physics in planar Ge hole quantum dots in an in-plane magnetic field, where the orbital terms play a dominant role in qubit physics, and provide a brief comparison with experimental measurements of the angular dependence of electrically driven spin resonance. We focus the theoretical analysis on electrical spin operation, phonon-induced relaxation, and the existence of coherence sweet spots. We find that the choice of magnetic field orientation makes a substantial difference for the properties of hole spin qubits. Specifically, we find that (i) EDSR for in-plane magnetic fields varies nonlinearly with the field strength and weaker than for perpendicular magnetic fields. (ii) The EDSR Rabi frequency is maximized when the a.c. electric field is aligned parallel to the magnetic field, and vanishes when the two are perpendicular. (iii) The orbital magnetic field terms make the in-plane g-factor strongly anisotropic in a squeezed dot, in excellent agreement with experimental measurements. (iv) Focusing on random telegraph noise, we show that the effect of noise in an in-plane magnetic field cannot be fully mitigated, as the orbital magnetic field terms expose the qubit to all components of the defect electric field. These findings will provide a guideline for experiments to design ultrafast, highly coherent hole spin qubits in Ge.

关键词： Layered semiconductors quantum dots Luttinger–Kohn model k dot p method

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Universal high-fidelity quantum gates for spin-qubits in diamond

arXiv

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arXiv 2024年

作者： Bartling, H.P. Yun, J. Schymik, K.N. van Riggelen, M. Enthoven, L.A. van Ommen, H.B. Babaie, M. Sebastiano, F. Markham, M. Twitchen, D.J. Taminiau, T.H. QuTech Delft University of Technology PO Box 5046 Delft2600 GA Netherlands Kavli Institute of Nanoscience Delft Delft University of Technology PO Box 5046 Delft2600 GA Netherlands Department of Quantum and Computer Engineering Delft University of Technology Delft2628 CJ Netherlands Department of Microelectronics Delft University of Technology Delft2628 CD Netherlands Element Six Fermi Avenue Harwell Oxford Didcot OxfordshireOX11 0QR United Kingdom

Spins associated to solid-state colour centers are a promising platform for investigating quantum computation and quantum networks. Recent experiments have demonstrated multi-qubit quantum processors, optical interconnects, and basic quantum error correction protocols. One of the key open challenges towards larger-scale systems is to realize high-fidelity universal quantum gates. In this work, we design and demonstrate a complete high-fidelity gate set for the two-qubit system formed by the electron and nuclear spin of a nitrogen-vacancy center in diamond. We use gate set tomography (GST) to systematically optimise the gates and demonstrate single-qubit gate fidelities of up to 99.999(1)% and a two-qubit gate fidelity of 99.93(5)%. Our gates are designed to decouple unwanted interactions and can be extended to other electron-nuclear spin systems. The high fidelities demonstrated provide new opportunities towards larger-scale quantum processing with colour-center qubits. Copyright © 2024, The Authors. All rights reserved.

关键词： Qubits

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Lindblad Tomography of a Superconducting quantum Processor

引用

Physical Review Applied 2022年第6期18卷 064056-064056页

作者： Gabriel O. Samach Ami Greene Johannes Borregaard Matthias Christandl Joseph Barreto David K. Kim Christopher M. McNally Alexander Melville Bethany M. Niedzielski Youngkyu Sung Danna Rosenberg Mollie E. Schwartz Jonilyn L. Yoder Terry P. Orlando Joel I-Jan Wang Simon Gustavsson Morten Kjaergaard William D. Oliver Research Laboratory of Electronics Massachusetts Institute of Technology Cambridge Massachusetts 02139 USA MIT Lincoln Laboratory Lexington Massachusetts 02421 USA 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 Cambridge Massachusetts 02139 USA

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 multiqubit 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 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.

关键词： quantum benchmarking quantum fluctuations & noise quantum information with solid state qubits quantum tomography Superconducting quantum optics Superconducting qubits Microwave techniques

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Design and demonstration of an operating system for executing applications on quantum network nodes

arXiv

引用

arXiv 2024年

作者： Donne, Carlo Delle Iuliano, Mariagrazia van der Vecht, Bart Ferreira, Guilherme M. Jirovská, Hana van der Steenhoven, Thom J.W. Dahlberg, Axel Skrzypczyk, Matt Fioretto, Dario Teller, Markus Filippov, Pavel Montblanch, Alejandro R.-P. Fischer, Julius van Ommen, H. Benjamin Demetriou, Nicolas Leichtle, Dominik Music, Luka Ollivier, Harold te Raa, Ingmar Kozlowski, Wojciech Taminiau, Tim H. Pawelczak, Przemyslaw Northup, Tracy E. Hanson, Ronald Wehner, Stephanie QuTech Kavli Institute of Nanoscience Delft University of Technology Delft2628 CJ Netherlands Quantum Computer Science Department of Software Technology Faculty of Electrical Engineering Mathematics and Computer Science Delft University of Technology Delft2628 XE Netherlands Embedded Systems Department of Software Technology Faculty of Electrical Engineering Mathematics and Computer Science Delft University of Technology Delft2628 XE Netherlands Institut für Experimentalphysik Universität Innsbruck Technikerstraße 25 Innsbruck6020 Austria QAT DIENS Ecole Normale Supérieure PSL University CNRS INRIA. 45 rue d’Ulm Paris75005 France LIP6 CNRS Sorbonne Université 4 Place Jussieu Paris75005 France

The goal of future quantum networks is to enable new internet applications that are impossible to achieve using solely classical communication[1, 2, 3]. Up to now, demonstrations of quantum network applications[4, 5, 6] and functionalities[7, 8, 9, 10, 11, 12] on quantum processors have been performed in ad-hoc software that was specific to the experimental setup, programmed to perform one single task (the application experiment) directly into low-level control devices using expertise in experimental physics. Here, we report on the design and implementation of the first architecture capable of executing quantum network applications on quantum processors in platform-independent high-level software. We demonstrate the architecture’s capability to execute applications in high-level software, by implementing it as a quantum network operating system – QNodeOS – and executing test programs including a delegated computation from a client to a server[13] on two quantum network nodes based on nitrogen-vacancy (NV) centers in diamond[14, 15]. We show how our architecture allows us to maximize the use of quantum network hardware, by multitasking different applications on a quantum network for the first time. Our architecture can be used to execute programs on any quantum processor platform corresponding to our system model, which we illustrate by demonstrating an additional driver for QNodeOS for a trapped-ion quantum network node based on a single 40Ca+atom[16]. Our architecture lays the groundwork for computer science research in the domain of quantum network programming, and paves the way for the development of software that can bring quantum network technology to society. Copyright © 2024, The Authors. All rights reserved.

关键词： Trapped ions

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