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arXiv 2025年

作者： Zanfardino, Gennaro Paesani, Stefano Leuzzi, Luca Santagati, Raffaele Illuminati, Fabrizio Ruocco, Giancarlo Leonetti, Marco Dipartimento di Ingegneria Industriale Università degli Studi di Salerno Via Giovanni Paolo II 132 SA Fisciano84084 Italy Institute of Nanotechnology of the National Research Council of Italy CNR-NANOTEC Rome Unit Piazzale A. Moro 5 RomeI-00185 Italy INFN Sezione di Napoli Gruppo Collegato di Salerno Italy NNF Quantum Computing Programme Niels Bohr Institute University of Copenhagen Blegdamsvej 17 Copenhagen ØDK-2100 Denmark The Niels Bohr Institute University of Copenhagen Copenhagen ØDK-2100 Denmark Department of Physics Sapienza University of Rome Piazzale A. Moro 5 RomeI-00185 Italy Quantum Lab Boehringer Ingelheim Ingelheim am Rhein55218 Germany Institute of Nanotechnology of the National Research Council of Italy CNR-NANOTEC Lecce Central Unit c/o Campus Ecotekne Via Monteroni Lecce73100 Italy Center for Life Nano- & Neuro-Science Italian Institute of Technology IIT Rome Italy

In the present work, we introduce, develop, and investigate a connection between multiphoton quantum interference, a core element of emerging photonic quantum technologies, and Hopfield-like Hamiltonians of classical neural networks, the paradigmatic models for associative memory and machine learning in systems of artificial intelligence. Specifically, we show that combining a system composed of Nph indistinguishable photons in superposition over M field modes, a controlled array of M binary phase-shifters, and a linear-optical interferometer, yields output photon statistics described by means of a p-body Hopfield Hamiltonian of M Ising-like neurons ±1, with p = 2Nph. We investigate in detail the generalized 4-body Hopfield model obtained through this procedure and show that it realizes a transition from a memory retrieval to a memory black-out regime, i.e. a spin-glass phase, as the amount of stored memory increases. The mapping enables novel routes to the realization and investigation of disordered and complex classical systems via efficient photonic quantum simulators, as well as the description of aspects of structured photonic systems in terms of classical spin Hamiltonians. © 2025, CC BY.

关键词： Hamiltonians

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Gate-tunable Superconductivity in Hybrid InSb-Pb Nanowires

arXiv

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arXiv 2023年

作者： Chen, Yan van Driel, David Lampadaris, Charalampos Khan, Sabbir A. Alattallah, Khalifah Zeng, Lunjie Olsson, Eva Dvir, Tom Krogstrup, Peter Liu, Yu 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 Physics Chalmers University of Technology Gothenburg41296 Sweden NNF Quantum Computing Programme Niels Bohr Institute University of Copenhagen Copenhagen2100 Denmark Danish Fundamental Metrology Hørsholm2970 Denmark

We present a report on hybrid InSb-Pb nanowires that combine high spin-orbit coupling with a high critical field and a large superconducting gap. Material characterization indicates the Pb layer of high crystal quality on the nanowire side facets. Hard induced superconducting gaps and gate-tunable supercurrent are observed in the hybrid nanowires. These results showcase the promising potential of this material combination for a diverse range of applications in hybrid quantum transport devices. © 2023, CC BY.

关键词： III-V semiconductors

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High-threshold quantum computing by fusing one-dimensional cluster states

arXiv

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arXiv 2022年

作者： Paesani, Stefano Brown, Benjamin J. Niels Bohr Institute University of Copenhagen Blegdamsvej 17 Copenhagen2100 Denmark NNF Quantum Computing Programme Niels Bohr Institute University of Copenhagen Denmark IBM Quantum T. J. Watson Research Center Yorktown HeightsNY10598 United States IBM Denmark Prøvensvej 1 Brøndby2605 Denmark

We propose a measurement-based model for fault-tolerant quantum computation that can be realised with one-dimensional cluster states and fusion measurements only;basic resources that are readily available with scalable photonic hardware. Our simulations demonstrate high thresholds compared with other measurement-based models realized with basic entangled resources and two-qubit fusion measurements. Its high tolerance to noise indicates that our practical construction offers a promising route to scalable quantum computing with quantum emitters and linear-optical elements. Copyright © 2022, The Authors. All rights reserved.

关键词： Cluster computing

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Ground-state phase diagram and parity-flipping microwave transitions in a gate-tunable Josephson junction

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Physical Review B 2024年第13期109卷 134506-134506页

作者： M. R. Sahu F. J. Matute-Cañadas M. Benito P. Krogstrup J. Nygård M. F. Goffman C. Urbina A. Levy Yeyati H. Pothier Quantronics group Service de Physique de l'État Condensé (CNRS UMR 3680) IRAMIS CEA-Saclay Université Paris-Saclay 91191 Gif-sur-Yvette France Departamento de Física Teórica de la Materia Condensada Condensed Matter Physics Center (IFIMAC) and Instituto Nicolás Cabrera Universidad Autónoma de Madrid 28049 Madrid Spain NNF Quantum Computing Programme Niels Bohr Institute University of Copenhagen Universitetsparken 5 2100 Copenhagen Denmark Center for Quantum Devices Niels Bohr Institute University of Copenhagen Universitetsparken 5 2100 Copenhagen Denmark

We probed a gate-tunable InAs nanowire Josephson weak link by coupling it to a microwave resonator. Tracking the resonator frequency shift when the weak link is close to pinch-off, we observe that the ground state of the latter alternates between a singlet and a doublet when varying either the gate voltage or the superconducting phase difference across it. The corresponding microwave absorption spectra display lines that approach zero energy close to the singlet-doublet boundaries, suggesting parity-flipping transitions, which are in principle forbidden in microwave spectroscopy and expected to arise only in tunnel spectroscopy. We tentatively interpret them by means of an ancillary state isolated in the junction acting as a reservoir for individual electrons.

关键词： Andreev reflection Circuit quantum electrodynamics Mesoscopics Nanowires quantum dots Anderson impurity model

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Gate-tunable Josephson diode in proximitized InAs supercurrent interferometers

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Physical Review Research 2023年第3期5卷 033131-033131页

作者： Carlo Ciaccia Roy Haller Asbjørn C. C. Drachmann Tyler Lindemann Michael J. Manfra Constantin Schrade Christian Schönenberger Quantum- and Nanoelectronics Lab Department of Physics University of Basel 4056 Basel Switzerland Center for Quantum Devices Niels Bohr Institute University of Copenhagen 2100 Copenhagen Denmark NNF Quantum Computing Programme Niels Bohr Institute University of Copenhagen 2100 Copenhagen Denmark Department of Physics and Astronomy Purdue University West Lafayette Indiana 47907 USA Birck Nanotechnology Center Purdue University West Lafayette Indiana 47907 USA Elmore Family School of Electrical and Computer Engineering Purdue University West Lafayette Indiana 47907 USA School of Materials Engineering Purdue University West Lafayette Indiana 47907 USA Swiss Nanoscience Institute University of Basel 4056 Basel Switzerland

The Josephson diode (JD) is a nonreciprocal circuit element that supports a larger critical current in one direction compared to the other. This effect has gained growing interest because of promising applications in superconducting electronic circuits with low power consumption. Some implementations of a JD rely on breaking the inversion symmetry in the material used to realize Josephson junctions (JJs), but recent theoretical proposals have suggested that the effect can also be engineered by combining two JJs hosting highly transmitting Andreev bound states in a Superconducting quantum Interference Device (SQUID) at a small, but finite flux bias. We have realized a SQUID with two JJs fabricated in a proximitized InAs two-dimensional electron gas (2DEG). We demonstrate gate control of the diode efficiency from zero up to around 30% at specific flux bias values which comes close to the maximum of ∼40% predicated in Souto et al. [Phys. Rev. Lett. 129, 267702 (2022)]. The key ingredients to the JD effect in the SQUID arrangement is the presence of highly transmitting channels in the JJs, a flux bias, and an asymmetry between the two SQUID arms.

关键词： Non-reciprocal transmission Proximity effect quantum transport Diodes III-V semiconductors Josephson junctions SQUID Superconducting devices Interferometry Microwave techniques

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Ground state phase diagram and "parity flipping" microwave transitions in a gate-tunable Josephson Junction

arXiv

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arXiv 2023年

作者： Sahu, M.R. Matute-Cañadas, F.J. Benito, M. Krogstrup, P. Nygård, J. Goffman, M.F. Urbina, C. Levy Yeyati, A. Pothier, H. Quantronics Group Service de Physique de l'État Condensé CNRS UMR 3680 IRAMIS CEA-Saclay Université Paris-Saclay Gif-sur-Yvette91191 France Instituto Nicolás Cabrera Universidad Autónoma de Madrid Madrid28049 Spain NNF Quantum Computing Programme Niels Bohr Institute University of Copenhagen Universitetsparken 5 Copenhagen2100 Denmark Center for Quantum Devices Niels Bohr Institute University of Copenhagen Universitetsparken 5 Copenhagen2100 Denmark

We probed a gate-tunable InAs nanowire Josephson weak link by coupling it to a microwave resonator. Tracking the resonator frequency shift when the weak link is close to pinch-off, we observe that the ground state of the latter alternates between a singlet and a doublet when varying either the gate voltage or the superconducting phase difference across it. The corresponding microwave absorption spectra display lines that approach zero energy close to the singlet-doublet boundaries, suggesting parity flipping transitions, which are in principle forbidden in microwave spectroscopy and expected to arise only in tunnel spectroscopy. We tentatively interpret them by means of an ancillary state isolated in the junction acting as a reservoir for individual electrons. Copyright © 2023, The Authors. All rights reserved.

关键词： Microwave resonators

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Subgap-state-mediated transport in superconductor–semiconductor hybrid islands: Weak and strong coupling regimes

arXiv

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arXiv 2024年

作者： Valentini, Marco Souto, Rubén Seoane Borovkov, Maksim Krogstrup, Peter Meir, Yigal Leijnse, Martin Danon, Jeroen Katsaros, Georgios Institute of Science and Technology Austria Am Campus 1 Klosterneuburg3400 Austria Madrid Spain Lund University Box 118 Lund22100 Sweden Center for Quantum Devices Niels Bohr Institute University of Copenhagen Copenhagen2100 Denmark NNF Quantum Computing Programme Niels Bohr Institute University of Copenhagen Universitetsparken 5 Copenhagen2100 Denmark Department of Physics Ben-Gurion University of the Negev Beer-Sheva84105 Israel Department of Physics Norwegian University of Science and Technology TrondheimNO-7491 Norway

Superconductor–semiconductor hybrid systems play a crucial role in realizing nanoscale quantum devices, including hybrid qubits, Majorana bound states, and Kitaev chains. For such hybrid devices, subgap states play a prominent role in their operation. In this work, we study such subgap states via Coulomb and tunneling spectroscopy through a superconducting island defined in a semiconductor nanowire fully coated by a superconductor. We systematically explore regimes ranging from an almost decoupled island to the open configuration. In the weak coupling regime, the experimental observations are very similar in the absence of a magnetic field and when one flux quantum is piercing the superconducting shell. Conversely, in the strong coupling regime, significant distinctions emerge between the two cases. We ascribe this different behavior to the existence of subgap states at one flux quantum, which become observable only for sufficiently strong coupling to the leads. We support our interpretation using a simple model to describe transport through the island. Our study highlights the importance of studying a broad range of tunnel couplings for understanding the rich physics of hybrid devices. © 2024, CC BY.

关键词： Superconducting materials

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Charge-4e supercurrent in a two-dimensional InAs-Al superconductor-semiconductor heterostructure

arXiv

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arXiv 2023年

作者： Ciaccia, Carlo Haller, Roy Drachmann, Asbjørn C.C. Lindemann, Tyler Manfra, Michael J. Schrade, Constantin Schönenberger, Christian Quantum- and Nanoelectronics Lab University of Basel BaselCH-4056 Switzerland Center for Quantum Devices Niels Bohr Institute University of Copenhagen Copenhagen2100 Denmark NNF Quantum Computing Programme Niels Bohr Institute 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 School of Electrical and Computer Engineering Purdue University West LafayetteIN47907 United States School of Materials Engineering Purdue University West LafayetteIN47907 United States Swiss Nanoscience Institute University of Basel Klingelbergstrasse 82 Basel Switzerland

Superconducting qubits with intrinsic noise protection offer a promising approach to improve the coherence of quantum information. Crucial to such protected qubits is the encoding of the logical quantum states into wavefunctions with disjoint support. Such encoding can be achieved by a Josephson element with an unusual charge-4e supercurrent emerging from the coherent transfer of pairs of Cooper-pairs. In this work, we demonstrate the controlled conversion of a conventional charge-2e dominated to a charge-4e dominated supercurrent in a superconducting quantum interference device (SQUID) consisting of gate-tunable planar Josephson junctions. We investigate the ac Josephson effect of the SQUID and measure a dominant photon emission at twice the fundamental Josephson frequency together with a doubling of the number of Shapiro steps, both consistent with the appearance of charge-4e supercurrent. Our results present a step towards novel protected superconducting qubits based on superconductor-semiconductor hybrid materials. Copyright © 2023, The Authors. All rights reserved.

关键词： SQUIDs

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Epitaxially Driven Phase Selectivity of Sn in Hybrid quantum Nanowires

arXiv

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arXiv 2022年

作者： Khan, Sabbir A. Martí-Sánchez, Sara Olsteins, Dags Lampadaris, Charalampos Carrad, Damon James Liu, Yu Quiñones, Judith Spadaro, Maria Chiara Jespersen, Thomas S. Krogstrup, Peter Arbiol, Jordi Center for Quantum Devices Niels Bohr Institute University of Copenhagen Copenhagen2100 Denmark Danish Fundamental Metrology Kogle Alle 5 Hørsholm2970 Denmark CSIC and BIST Campus UAB Bellaterra Catalonia Barcelona08193 Spain Department of Energy Conversion and Storage Technical University of Denmark Fysikvej Building 310 Lyngby2800 Denmark NNF Quantum Computing Programme Niels Bohr Institute University of Copenhagen Denmark ICREA Pg. Lluís Companys 23 Catalonia Barcelona08010 Spain

Hybrid semiconductor/superconductor nanowires constitute a pervasive platform for studying gate-tunable superconductivity and the emergence of topological behavior. Their low-dimensionality and crystal structure flexibility facilitate novel heterostructure growth and efficient material optimization;crucial prerequisites for accurately constructing complex multi-component quantum materials. Here, we present an extensive optimization of Sn growth on InSb, InAsSb and InAs nanowires. We demonstrate how the growth conditions and the crystal structure/symmetry of the semiconductor drive the formation of either semi-metallic α − Sn or superconducting β − Sn. For InAs nanowires, we obtain phase-pure, superconducting β − Sn shells. However, for InSb and InAsSb nanowires, an initial epitaxial α − Sn phase evolves into a polycrystalline shell of coexisting α and β phases, where the β/α volume ratio increases with Sn shell thickness. Whether these nanowires exhibit superconductivity or not critically relies on the β − Sn content. Therefore, this work provides key insights into Sn phase control on a variety of semiconductors, with consequences for the yield of superconducting hybrids suitable for generating topological systems. © 2022, CC BY-NC-ND.

关键词： Nanowires

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Gate Tunable Josephson Diode in Proximitized InAs Supercurrent Interferometers

arXiv

引用

arXiv 2023年

作者： Ciaccia, Carlo Haller, Roy Drachmann, Asbjørn C.C. Lindemann, Tyler Manfra, Michael J. Schrade, Constantin Schönenberger, Christian Quantum- and Nanoelectronics Lab Department of Physics University of Basel Basel4056 Switzerland Center for Quantum Devices Niels Bohr Institute University of Copenhagen Copenhagen2100 Denmark NNF Quantum Computing Programme Niels Bohr Institute 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 Swiss Nanoscience Institute University of Basel Basel4056 Switzerland

The Josephson diode (JD) is a non-reciprocal circuit element that supports a larger critical current in one direction compared to the other. This effect has gained a growing interest because of promising applications in superconducting electronic circuits with low power consumption. Some implementations of a JD rely on breaking the inversion symmetry in the material used to realize Josephson junctions (JJs), but recent theoretical proposals have suggested that the effect can also be engineered by combining two JJs hosting highly transmitting Andreev bound states in a Superconducting quantum Interference Device (SQUID) at a small, but finite flux bias. We have realized a SQUID with two JJs fabricated in a proximitized InAs two-dimensional electron gas (2DEG). We demonstrate gate control of the diode efficiency from zero up to around 30% at specific flux bias values which comes close to the maximum of ∼ 40% predicated in Ref. [R. S. Souto, M. Leijnse and C. Schrade, Phys. Rev. Lett. 129, 267702 (2022)]. The key ingredients to the JD effect in the SQUID arrangement is the presence of highly transmitting channels in the JJs, a flux bias and an asymmetry between the two SQUID arms. © 2023, CC BY.

关键词： SQUIDs

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