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Collective Formation of Misfit Dislocations at the Critical Thickness for Equilibrium Nanowire Heterostructures

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SSRN

SSRN 2023年

作者： Nikolajsen, Thue Christian Thann Krogstrup, Peter Schuwalow, Sergej Særkjær, Tobias Skov NNF Quantum Computing Programme Niels Bohr Institute University of Copenhagen Copenhagen2100 Denmark Center for Quantum Devices Niels Bohr Institute University of Copenhagen Copenhagen2100 Denmark

In this work we model the evolution of strain energy during different growth stages of heterostructure nanowires. We find that the minimum energy configuration changes abruptly from fully elastically strained to partially relaxed due to collective formation of a misfit dislocation network. The transition at the critical thickness is associated with a characteristic density of *** insights are gained from a technique developed to simulate misfit dislocations in a finite element framework, incorporating both elastic and plastic relaxation. We argue that these results have general relevance for mismatched heterostructures. © 2023, The Authors. All rights reserved.

关键词： Crystal structure

Collective formation of misfit dislocations at the critical thickness for equilibrium nanowire heterostructures

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arXiv 2021年

作者： Thann, Thue Christian Særkjær, Tobias Schuwalow, Sergej Krogstrup, Peter NNF Quantum Computing Programme Niels Bohr Institute University of Copenhagen Copenhagen2100 Denmark Center for Quantum Devices Niels Bohr Institute University of Copenhagen Copenhagen2100 Denmark

In this work we model the evolution of strain energy during different growth stages of heterostructure nanowires. We find that the minimum energy configuration changes abruptly from fully elastically strained to partially relaxed due to collective formation of a misfit dislocation network. The transition at the critical thickness is associated with a characteristic density of misfits. These insights are gained from a technique developed to simulate misfit dislocations in a finite element framework, incorporating both elastic and plastic relaxation in a stationary heterostructure. We argue that these results have general relevance for mismatched heterostructures. © 2021, CC BY.

关键词： Heterojunctions

Purifying Photon Indistinguishability through quantum Interference

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Physical Review Letters 2024年第3期133卷 033604-033604页

作者： Carlos F. D. Faurby Lorenzo Carosini Huan Cao Patrik I. Sund Lena M. Hansen Francesco Giorgino Andrew B. Villadsen Stefan N. van den Hoven Peter Lodahl Stefano Paesani Juan C. Loredo Philip Walther Center for Hybrid Quantum Networks (Hy-Q) Niels Bohr Institute Faculty of Physics Vienna Center for Quantum Science and Technology (VCQ) 1090 Vienna Austria Christian Doppler Laboratory for Photonic Quantum Computer Faculty of Physics MESA+ Institute for Nanotechnology NNF Quantum Computing Programme Niels Bohr Institute Research Network for Quantum Aspects of Space Time (TURIS) 1090 Vienna Austria Institute for Quantum Optics and Quantum Information (IQOQI) Vienna Austrian Academy of Sciences Vienna Austria

Indistinguishability between photons is a key requirement for scalable photonic quantum technologies. We experimentally demonstrate that partly distinguishable single photons can be purified to reach near-unity indistinguishability by the process of quantum interference with ancillary photons followed by heralded detection of a subset of them. We report on the indistinguishability of the purified photons by interfering two purified photons and show improvements in the photon indistinguishability of 2.774(3)% in the low-noise regime, and as high as 10.2(5)% in the high-noise regime.

关键词： quantum circuits quantum communication, protocols & technology quantum protocols quantum state engineering Single photon sources Optical interferometry

Self-correcting GKP qubit and gates in a driven-dissipative circuit

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arXiv 2024年

作者： Nathan, Frederik O’Brien, Liam Noh, Kyungjoo Matheny, Matthew H. Grimsmo, Arne L. Jiang, Liang Refael, Gil Center for Quantum Devices and NNF Quantum Computing Programme Niels Bohr Institute University of Copenhagen Copenhagen2100 Denmark Department of Physics Institute for Quantum Information and Matter California Institute of Technology PasadenaCA91125 United States AWS Center for Quantum Computing PasadenaCA91125 United States Pritzker School of Molecular Engineering The University of Chicago ChicagoIL60637 United States

We propose a circuit architecture for a dissipatively error-corrected GKP qubit. The device consists of a high-impedance LC circuit coupled to a Josephson junction and a resistor via a controllable switch. When the switch is activated via a particular family of stepwise protocols, the resistor absorbs all noise-induced entropy, resulting in dissipative error correction of both phase and amplitude errors. This leads to an exponential increase of qubit lifetime, reaching beyond 10ms in simulations with near-feasible parameters. We show that the lifetime remains exponentially long in the presence of extrinsic noise and device/control imperfections (e.g., due to parasitics and finite control bandwidth) under specific thresholds. In this regime, lifetime is likely only limited by phase slips and quasiparticle tunneling. We show that the qubit can be read out and initialized via measurement of the supercurrent in the Josephson junction. We finally show that the qubit supports native self-correcting single-qubit Clifford gates, where dissipative error-correction of control noise leads to exponential suppression of gate infidelity. Copyright © 2024, The Authors. All rights reserved.

关键词： Resistors

Hardware requirements for realizing a quantum advantage with deterministic single-photon sources

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Physical Review A 2024年第4期109卷 042613-042613页

作者： Patrik I. Sund Ravitej Uppu Stefano Paesani Peter Lodahl Center for Hybrid Quantum Networks (Hy-Q) Niels Bohr Institute University of Copenhagen Blegdamsvej 17 DK-2100 Copenhagen Denmark Department of Physics & Astronomy University of Iowa Iowa City Iowa 52242 USA NNF Quantum Computing Programme Niels Bohr Institute University of Copenhagen Blegdamsvej 17 Copenhagen 2100 Denmark

Boson sampling is a specialized algorithm native to the quantum photonic platform developed for near-term demonstrations of quantum advantage over classical computers. While clear useful applications for such near-term pre-fault-tolerance devices are not currently known, reaching a quantum advantage regime serves as a useful benchmark for the hardware. Here, we analyze and detail hardware requirements needed to reach quantum advantage with deterministic quantum emitters, a promising platform for photonic quantum computing. We elucidate key steps that can be taken in experiments to overcome practical constraints and establish quantitative hardware-level requirements. We find that quantum advantage is within reach using quantum emitters with an efficiency of 60%–70% and interferometers constructed according to a hybrid-mode-encoding architecture, constituted of Mach-Zehnder interferometers with an insertion loss of 0.0035dB (a transmittance of 99.92%) per component.

关键词： Optical quantum information processing quantum algorithms & computation quantum benchmarking Single photon sources

Superconducting Proximity Effect in Two-Dimensional Hole Gases

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arXiv 2024年

作者： Babkin, Serafim Joecker, Benjamin Flensberg, Karsten Serbyn, Maksym Danon, Jeroen Am Campus 1 Klosterneuburg3400 Austria Center for Quantum Devices Niels Bohr Institute University of Copenhagen CopenhagenDK-2100 Denmark NNF Quantum Computing Programme Niels Bohr Institute University of Copenhagen Denmark Department of Physics Norwegian University of Science and Technology TrondheimNO-7491 Norway

Technology involving hybrid superconductor–semiconductor materials is a promising avenue for engineering quantum devices for information storage, manipulation, and transmission. Proximity-induced superconducting correlations are an essential part of such devices. While the proximity effect in the conduction band of common semiconductors is well understood, its manifestation in confined hole gases, realized for instance in germanium, is an active area of research. Lower-dimensional hole-based systems, particularly in germanium, are emerging as an attractive platform for a variety of solid-state quantum devices, due to their combination of efficient spin and charge control and long coherence times. The recent experimental realization of the proximity effect in germanium thus calls for a theoretical description that is tailored to hole gases. In this work, we propose a simple model to describe proximity-induced superconductivity in two-dimensional hole gases, incorporating both the heavy-hole (HH) and light-hole (LH) bands. We start from the Luttinger–Kohn model, introduce three parameters that characterize hopping across the superconductor–semiconductor interface, and derive explicit intraband and interband effective pairing terms for the HH and LH bands. Unlike previous approaches, our theory provides a quantitative relationship between induced pairings and interface properties. Restricting our general model to an experimentally relevant case where only the HH band crosses the chemical potential, we predict the coexistence of s-wave and d-wave singlet pairings, along with triplet-type pairings, and modified Zeeman and Rashba spin–orbit couplings. Our model thus presents a starting point for theoretical modeling of quantum devices based on proximitized hole gases, fueling further progress in quantum technology. Copyright © 2024, The Authors. All rights reserved.

关键词： Shear waves

High-Threshold quantum computing by Fusing One-Dimensional Cluster States

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Physical Review Letters 2023年第12期131卷 120603-120603页

作者： Stefano Paesani Benjamin J. Brown Center for Hybrid Quantum Networks (Hy-Q) Niels Bohr Institute University of Copenhagen Blegdamsvej 17 Copenhagen 2100 Denmark NNF Quantum Computing Programme Niels Bohr Institute University of Copenhagen Blegdamsvej 17 Copenhagen 2100 Denmark IBM Quantum T. J. Watson Research Center Yorktown Heights New York 10598 USA IBM Denmark Prøvensvej 1 Brøndby 2605 Denmark

We propose a measurement-based model for fault-tolerant quantum computation that can be realized 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 2-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.

关键词： Measurement-based quantum computing Optical quantum information processing quantum computation quantum error correction quantum information architectures & platforms

Gatemon Qubit Revisited for Improved Reliability and Stability

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arXiv 2024年

作者： Feldstein-Bofill, David Sun, Zhenhai Wied, Casper Singh, Shikhar Isakov, Brian D. Krøjer, Svend Hastrup, Jacob Gyenis, András Kjaergaard, Morten Center for Quantum Devices Niels Bohr Institute University of Copenhagen Denmark NNF Quantum Computing Programme Niels Bohr Institute University of Copenhagen Denmark Department of Electrical Computer & Energy Engineering University of Colorado Boulder BoulderCO80309 United States Department of Physics University of Colorado Boulder BoulderCO80309 United States

The development of quantum circuits based on hybrid superconductor-semiconductor Josephson junctions holds promise for exploring their mesoscopic physics and for building novel superconducting devices. The gate-tunable superconducting transmon qubit (gatemon) is the paradigmatic example of such a superconducting circuit. However, gatemons typically suffer from unstable and hysteretic qubit frequencies with respect to the applied gate voltage and reduced coherence times. Here we develop methods for characterizing these challenges in gatemons and deploy these methods to compare the impact of shunt capacitor designs on gatemon performance. Our results indicate a strong frequency- and design-dependent behavior of the qubit stability, hysteresis, and dephasing times. Moreover, we achieve highly reliable tuning of the qubit frequency with 1 MHz precision over a range of several GHz, along with improved stability in grounded gatemons compared to gatemons with a floating capacitor design. © 2024, CC BY.

关键词： Qubits

Programmable Photonic Nonlinearity for quantum Simulation

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Programmable Photonic Nonlinearity for Quantum Simulation

Asia Communications and Photonics Conference and Exhibition (ACP)

作者： Ying Wang Kasper H. Nielsen Edward Deacon Patrik I. Sund Zhe Liu Sven Scholz Arne Ludwig Leonardo Midolo Anders S. Sørensen Stefano Paesani Peter Lodahl Center for Hybrid Quantum Networks (Hy-Q) Niels Bohr Institute University of Copenhagen Copenhagen Denmark Quantum Engineering and Technology Laboratories School of Physics Bristol UK Department of Electrical and Electronic Engineering University of Bristol Bristol UK Lehrstuhl für Angewandte Festkörperphysik Ruhr-Universität Bochum Bochum Germany Center for Hybrid Quantum Networks (Hy-Q) NNF Quantum Computing Programme Niels Bohr Institute University of Copenhagen Copenhagen Denmark

ISBN: (数字)9798350379266

ISBN: (纸本)9798350379273

Light-matter interaction at the quantum level provides a versatile interface driving photonic quantum technologies toward practical applications. We demonstrate multi-mode photonic circuits that enable precise programming of linear and nonlinear phase configurations at the single-photon level. The nonlinearity operation is realized using a solid-state quantum emitter, a self-assembled quantum dot, integrated into a nanophotonic device. The quantum dot interfaces with a temporal linear optical interferometer, creating a programmable nonlinear photonic platform that is necessary for implementing quantum protocols that require strong nonlinearities, such as the quantum simulation of anharmonic molecular dynamics.

关键词： Optical interferometry Self-assembly Protocols Stimulated emission quantum dots Programming Nonlinear optical devices Optical fiber communication Photonics quantum simulation