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Author Correction: Lightcone bounds for quantum circuit mapping via uncomplexity

npj quantum Information 2024年第1期10卷 1页

作者： Matthew Steinberg Medina Bandić Sacha Szkudlarek Aritra Sarkar Sebastian Feld Carmen G. Almudever Quantum Computing Division QuTech Delft University of Technology Delft the Netherlands Department of Quantum & Computer Engineering Delft University of Technology Delft the Netherlands Computer Engineering Department Technical University of Valencia Valencia Spain

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A scalable quantum gate-based implementation for causal hypothesis testing

arXiv

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arXiv 2022年

作者： Kundu, Akash Acharya, Tamal Sarkar, Aritra Institute of Theoretical and Applied Informatics Polish Academy of Sciences Joint Doctoral School Silesian University of Technology Gliwice Poland Quantum Intelligence Research Team Department of Quantum & Computer Engineering Delft University of Technology Delft2628 CD Netherlands Quantum Machine Learning Group Quantum Computing Division QuTech Delft2628 CJ Netherlands

In this work, we study quantum computing algorithms for accelerating causal inference. Specifically, we consider the formalism of causal hypothesis testing presented in [Nat Commun 10, 1472 (2019)]. We develop a quantum circuit implementation and use it to demonstrate that the error probability introduced in the previous work requires modification. The practical scenario, which follows a theoretical description, is constructed as a scalable quantum gate-based algorithm on IBM Qiskit. We present the circuit construction of the oracle embedding the causal hypothesis and assess the associated gate complexities. Additionally, our experiments on a simulator platform validate the predicted speedup. We discuss applications of this framework for causal inference use cases in bioinformatics and artificial general intelligence. © 2022, CC BY.

关键词： Inference engines

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Variational quantum algorithm for enhanced continuous variable optical phase sensing

arXiv

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arXiv 2023年

作者： Nielsen, Jens A.H. Kicinski, Mateusz Arge, Tummas N. Vijayadharan, Kannan Foldager, Jonathan Borregaard, Johannes Meyer, Johannes Jakob Neergaard-Nielsen, Jonas S. Gehring, Tobias Andersen, Ulrik L. Center for Macroscopic Quantum States bigQ Department of Physics Technical University of Denmark Fysikvej 307 Kgs. LyngbyDK-2800 Denmark Department of Information Engineering University of Padova Italy Department of Applied Mathematics and Computer Science Technical University of Denmark Denmark Qutech Delft University of Technology Netherlands Department of Physics Harvard University United States Dahlem Center for Complex Quantum Systems Freie Universität Berlin Germany

Variational quantum algorithms (VQAs) are hybrid quantum-classical approaches used for tackling a wide range of problems on noisy intermediate-scale quantum (NISQ) devices. Testing these algorithms on relevant hardware is crucial to investigate the effect of noise and imperfections and to assess their practical value. Here, we implement a variational algorithm designed for optimized parameter estimation on a continuous variable platform based on squeezed light, a key component for high-precision optical phase estimation. We investigate the ability of the algorithm to identify the optimal metrology process, including the optimization of the probe state and measurement strategy for small-angle optical phase sensing. Two different optimization strategies are employed, the first being a gradient descent optimizer using Gaussian parameter shift rules to estimate the gradient of the cost function directly from the measurements. The second strategy involves a gradient-free Bayesian optimizer, fine-tuning the system using the same cost function and trained on the data acquired through the gradient-dependent algorithm. We find that both algorithms can steer the experiment towards the optimal metrology process. However, they find minima not predicted by our theoretical model, demonstrating the strength of variational algorithms in modelling complex noise environments, a non-trivial task. Copyright © 2023, The Authors. All rights reserved.

关键词： Cost functions

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Efficient Qubit Calibration by Binary-Search Hamiltonian Tracking

arXiv

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arXiv 2025年

作者： Berritta, Fabrizio Benestad, Jacob Pahl, Lukas Mathews, Melvin Krzywda, Jan A. Assouly, Réouven Sung, Youngkyu Kim, David K. Niedzielski, Bethany M. Serniak, Kyle Schwartz, Mollie E. Yoder, Jonilyn L. Chatterjee, Anasua Grover, Jeffrey A. Danon, Jeroen Oliver, William D. Kuemmeth, Ferdinand Research Laboratory of Electronics Massachusetts Institute of Technology CambridgeMA02139 United States Center for Quantum Devices Niels Bohr Institute University of Copenhagen Copenhagen2100 Denmark Center for Quantum Spintronics Department of Physics Norwegian University of Science and Technology TrondheimNO-7491 Norway Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology CambridgeMA02139 United States Department of Information Technology and Electrical Engineering ETH Zürich Zürich8093 Switzerland 〈aQaL〉 Applied Quantum Algorithms — Lorentz Insitute for Theoretical Physics & Leiden Institute of Advanced Computer Science Universiteit Leiden Netherlands Lincoln Laboratory Massachusetts Institute of Technology LexingtonMA02421 United States QuTech and Kavli Institute of Nanoscience Delft University of Technology Delft Netherlands Department of Physics Massachusetts Institute of Technology CambridgeMA02139 United States Institute of Experimental and Applied Physics University of Regensburg Regensburg93040 Germany QDevil Quantum Machines Ballerup2750 Denmark

We present a real-time method for calibrating the frequency of a resonantly driven qubit. The real-time processing capabilities of a classical controller dynamically generate adaptive probing sequences for qubit-frequency estimation. Each probing evolution time and drive frequency are calculated to divide the prior probability distribution into two branches, following a locally optimal strategy that mimics a conventional binary search. We show the algorithm’s efficacy by stabilizing a flux-tunable transmon qubit, leading to improved coherence and gate fidelity. By feeding forward the updated qubit frequency, the FPGA-powered control electronics partially mitigates non-Markovian noise in the system, which is detrimental to quantum error correction. Our protocol highlights the importance of feedback in improving the calibration and stability of qubits subject to drift and can be readily applied to other qubit platforms. © 2025, CC BY.

关键词： Hamiltonians

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Integrated Phononic Waveguides in Diamond

arXiv

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arXiv 2023年

作者： Ding, Sophie Weiyi Pingault, Benjamin Shao, Linbo Sinclair, Neil Machielse, Bartholomeus Chia, Cleaven Maity, Smarak Lončar, Marko John A. Paulson School of Engineering and Applied Sciences Harvard University CambridgeMA02138 United States QuTech Kavli Institute of Nanoscience Delft University of Technology PO Box 5046 Delft2600 GA Netherlands Bradley Department of Electrical and Computer Engineering Virginia Tech BlacksburgVA24061 United States AWS Center for Quantum Networking BostonMA02135 United States

Efficient generation, guiding, and detection of phonons, or mechanical vibrations, are of interest in various fields including radio frequency communication, sensing, and quantum information. Diamond is an important platform for phononics because of the presence of strain-sensitive spin qubits, and its high Young’s modulus which allows for low-loss gigahertz devices. We demonstrate a diamond phononic waveguide platform for generating, guiding, and detecting gigahertz-frequency surface acoustic wave (SAW) phonons. We generate SAWs using interdigital transducers integrated on AlN/diamond and observe SAW transmission at 4-5 GHz through both ridge and suspended waveguides, with wavelength-scale cross sections (~1 μm2) to maximize spin-phonon interaction. This work is a crucial step for developing acoustic components for quantum phononic circuits with strain-sensitive color centers in diamond. Copyright © 2023, The Authors. All rights reserved.

关键词： Diamonds

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Near-term n to k distillation protocols using graph codes

arXiv

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arXiv 2023年

作者： Goodenough, Kenneth De Bone, Sébastian Addala, Vaishnavi Krastanov, Stefan Jansen, Sarah Gijswijt, Dion Elkouss, David QuTech Delft University of Technology Netherlands College of Information and Computer Science University of Massachusetts Amherst United States Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology United States Delft Institute of Applied Mathematics Delft University of Technology Netherlands Korteweg-de Vries Institute for Mathematics University of Amsterdam Netherlands Networked Quantum Devices Unit Okinawa Institute of Science and Technology Graduate University Japan

Noisy hardware forms one of the main hurdles to the realization of a near-term quantum internet. Distillation protocols allows one to overcome this noise at the cost of an increased overhead. We consider here an experimentally relevant class of distillation protocols, which distill n to k end-to-end entangled pairs using bilocal Clifford operations, a single round of communication and a possible final local operation depending on the observed measurement outcomes. In the case of permutationally invariant depolarizing noise on the input states, we find a correspondence between these distillation protocols and graph codes. We leverage this correspondence to find provably optimal distillation protocols in this class for several tasks important for the quantum internet. This correspondence allows us to investigate use cases for so-called non-trivial measurement syndromes. Furthermore, we detail a recipe to construct the circuit used for the distillation protocol given a graph code. We use this to find circuits of short depth and small number of two-qubit gates. Additionally, we develop a black-box circuit optimization algorithm, and find that both approaches yield comparable circuits. Finally, we investigate the teleportation of encoded states and find protocols which jointly improve the rate and fidelities with respect to prior art. © 2023, CC BY.

关键词： quantum entanglement

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Limitations of nearest-neighbor quantum networks

引用

Physical Review A 2022年第1期106卷 L010401-L010401页

作者： F. Hahn A. Dahlberg J. Eisert A. Pappa Dahlem Center for Complex Quantum Systems Freie Universität Berlin 14195 Berlin Germany Department of Electrical Engineering and Computer Science Technische Universität Berlin 10587 Berlin Germany QuTech TU Delft 2628CJ Delft The Netherlands Fraunhofer Heinrich Hertz Institute 10587 Berlin Germany Department of Electrical Engineering and Computer Science Technische Universität Berlin 10587 Berlin Germany Fraunhofer Institute for Open Communication Systems-FOKUS 10589 Berlin Germany

quantum communication research has in recent years shifted to include multipartite networks for which questions of quantum network routing naturally emerge. To understand the potential for multipartite routing, we focus on the most promising architectures for future quantum networks—those connecting nodes close to each other. Nearest-neighbor networks, such as rings, lines, and grids, have been studied under different communication scenarios to facilitate the sharing of quantum resources especially in the presence of bottlenecks. We analyze the potential of nearest-neighbor entangling gate quantum networks and identify some serious limitations by demonstrating that rings and lines cannot overcome common bottleneck communication problems.

关键词： Entanglement manipulation quantum communication quantum entanglement quantum information theory quantum networks quantum repeaters

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Topological-Graph Dependencies and Scaling Properties of a Heuristic Qubit-Assignment Algorithm

arXiv

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arXiv 2021年

作者： Steinberg, Matthew Feld, Sebastian Almudever, Carmen G. Marthaler, Michael Reiner, Jan-Michael QuTech Delft University of Technology Delft Netherlands Quantum and Computer Engineering Department Delft University of Technology Delft Netherlands HQS Quantum Simulations GmbH Haid-und-Neu-Straße 7 KarlsruheD-76131 Germany Computer Engineering Department Technical University of Valencia Valencia Spain

The qubit-mapping problem aims to assign and route qubits of a quantum circuit onto a NISQ device in an optimized fashion, with respect to some cost function. Finding an optimal solution to this problem is known to scale exponentially in computational complexity;as such, it is imperative to investigate scalable qubit-mapping solutions for NISQ computation. In this work, a noise-aware heuristic qubit-assignment algorithm (which assigns initial placements for qubits in a quantum algorithm to qubits on a NISQ device, but does not route qubits during the quantum algorithm's execution) is presented and compared against the optimal brute-force solution, as well as a trivial qubit assignment, with the aim to quantify the performance of our heuristic qubit-assignment algorithm. We find that for small, connected-graph algorithms, our heuristic-assignment algorithm faithfully lies in between the effective upper and lower bounds given by the brute-force and trivial qubit-assignment algorithms. Additionally, we find that the topological-graph properties of quantum algorithms with over six qubits play an important role in our heuristic qubit-assignment algorithm's performance on NISQ devices. Finally, we investigate the scaling properties of our heuristic algorithm for quantum processors with up to 100 qubits;here, the algorithm was found to be scalable for quantum-algorithms which admit path-like graphs. Our findings show that as the size of the quantum processor in our simulation grows, so do the benefits from utilizing the heuristic qubit-assignment algorithm, under particular constraints for our heuristic algorithm. This work thus characterizes the performance of a heuristic qubit-assignment algorithm with respect to the topological-graph and scaling properties of a quantum algorithm which one may wish to run on a given NISQ device. Copyright © 2021, The Authors. All rights reserved.

关键词： Heuristic algorithms

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Satellite-assisted quantum communication with single photon sources and atomic memories

arXiv

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arXiv 2024年

作者： Domínguez Tubío, V. Badás Aldecocea, M. van Dam, J. Sørensen, A.S. Borregaard, J. QuTech Delft University of Technology Delft2628 CJ Netherlands Kavli Institute of Nanoscience Delft University of Technology Delft2628 CJ Netherlands Space Engineering Department Delft University of Technology Delft2629 HS Netherlands Quantum Computer Science EEMCS Delft University of Technology Delft2628 CJ Netherlands Niels Bohr Institute University of Copenhagen Blegdamsvej 17 CopenhagenDK-2100 Denmark Department of Physics Harvard University CambridgeMA02138 United States

Satellite-based quantum repeaters are a promising means to reach global distances in quantum networking due to the polynomial decrease of optical transmission with distance in free space, in contrast to the exponential decrease in optical fibers. We propose a satellite-based quantum repeater architecture with trapped individual atomic qubits, which can serve both as quantum memories and true single photon sources. This hardware allows for nearly deterministic Bell measurements and exhibits long coherence times without the need for costly cryogenic technology in space. We develop a detailed analytical model of the repeater, which includes the main imperfections of the quantum hardware and the optical link, allowing us to estimate that high-rate and high-fidelity entanglement distribution can be achieved over inter-continental distances. In particular, we find that high fidelity entanglement distribution over thousands of kilometres at a rate of 100 Hz can be achieved with orders of magnitude fewer memory modes than conventional architectures based on optical Bell state measurements. © 2024, CC BY.

关键词： quantum entanglement

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

arXiv

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arXiv 2023年

作者： Sarkar, Abhikbrata Wang, Zhanning Rendell, Matthew Hendrickx, Nico W. Veldhorst, Menno Scappucci, Giordano Khalifa, Mohammad Salfi, Joe Saraiva, Andre Dzurak, A.S. Hamilton, A.R. Culcer, Dimitrie School of Physics The University of New South Wales Sydney2052 Australia QuTech and Kavli Institute of Nanoscience Delft University of Technology Delft2628 CJ Netherlands Department of Electrical and Computer Engineering University of British Columbia VancouverBC Canada Quantum Matter Institute University of British Columbia VancouverBC Canada School of Electrical Engineering and Telecommunications The University of New South Wales Sydney2052 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 stage 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. Furthermore, although the Schrieffer-Wolff approximation can describe electron dipole spin resonance (EDSR), it does not capture the fundamental spin dynamics underlying qubit coherence. Specifically, we find that: (i) EDSR for in-plane magnetic fields varies non-linearly 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 coherence sweet spots do not exist in an in-plane magnetic field, 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. © 2023, CC BY.

关键词： Magnetic fields

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