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Hydrophilic direct bonding of (100) diamond and a deposited SiO2 substrates

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arXiv 2025年

作者： Chen, Tianyin Hermias, Jeffrel Nur, Salahuddin Ishihara, Ryoichi Department of Quantum and Computer Engineering Delft University of Technology Netherlands QuTech Delft University of Technology Netherlands

Diamond has emerged as a leading material for solid-state spin quantum systems and extreme environment electronics. However, a major limitation is that most diamond devices and structures are fabricated using bulk diamond plates. The absence of a suitable diamond-on-insulator (DOI) substrate hinders the advanced nanofabrication of diamond quantum and electronic devices, posing a significant roadblock to large-scale, on-chip diamond quantum photonics and electronics systems. In this work, we demonstrate the direct bonding of (100) single-crystal (SC) diamond plates to PECVD-grown SiO2/Si substrates at low temperatures and atmospheric conditions. The surfaces of the SiO2 and diamond plates are then activated using oxygen plasma and piranha solution, respectively. Bonding occurs when the substrates are brought into contact with water in between and annealed at 200°C under atmospheric conditions, resulting in a DOI substrate. We systematically studied the influence of piranha solution treatment time and diamond surface roughness on the shear strength of the bonded substrate, devising an optimal bonding process that achieves a high yield rate of 90% and a maximum shear strength of 9.6 MPa. X-ray photoelectron spectroscopy (XPS) was used for quantitative analysis of the surface chemicals at the bonding interface. It appears that the amount of -OH bindings increases with the initial roughness of the diamond, facilitating the strong bonding with the SiO2. This direct bonding method will pave the way for scalable manufacturing of diamond nanophotonic devices and enable large-scale integration of diamond quantum and electronic systems. © 2025, CC BY-NC-ND.

关键词： Bonding

EO-GRAPE and EO-DRLPE: Open and Closed Loop Approaches for Energy Efficient quantum Optimal Control

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arXiv 2024年

作者： Fauquenot, Sebastiaan Sarkar, Aritra Feld, Sebastian Quantum Machine Learning Research Group Quantum Computing Division QuTech Netherlands Department of Quantum & Computer Engineering Delft University of Technology Netherlands

This research investigates the possibility of using quantum optimal control techniques to co-optimize the energetic cost and the process fidelity of a quantum unitary gate. The energetic cost is theoretically defined, and thereby, the gradient of the energetic cost for pulse engineering is derived. We empirically demonstrate the Pareto optimality in the trade-off between process fidelity and energetic cost. Thereafter, two novel numerical quantum optimal control approaches are proposed: (i) energy-optimized gradient ascent pulse engineering (EO-GRAPE) as an open-loop gradient-based method, and (ii) energy-optimized deep reinforcement learning for pulse engineering (EO-DRLPE) as a closed-loop method. The performance of both methods is probed in the presence of increasing noise. We find that the EO-GRAPE method performs better than the EO-DRLPE methods with and without a warm start for most experimental settings. Additionally, for one qubit unitary gate, we illustrate the correlation between the Bloch sphere path length and the energetic cost. © 2024, CC BY-NC-ND.

关键词： Deep reinforcement learning

Near-Term Spin-Qubit Architecture Design via Multipartite Maximally Entangled States

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PRX quantum 2025年第2期6卷 020307-020307页

作者： N. Paraskevopoulos M. Steinberg B. Undseth A. Sarkar L.M.K. Vandersypen X. Xue S. Feld QuTech Delft University of Technology Delft Netherlands Quantum and Computer Engineering Department Delft University of Technology Delft Netherlands Kavli Institute of Nanoscience Delft University of Technology Delft Netherlands

The design and benchmarking of quantum computer architectures traditionally rely on practical hardware restrictions, such as gate fidelities, control, and cooling. At the theoretical and software levels, numerous approaches have been proposed for benchmarking quantum devices, ranging from, inter alia, quantum volume to randomized benchmarking. In this work, we utilize the quantum information-theoretic properties of multipartite maximally entangled quantum states, in addition to their correspondence with quantum error-correction codes, permitting us to quantify the entanglement generated on near-term bilinear spin-qubit architectures. For this aim, we introduce four metrics that ascertain the quality of genuine multipartite quantum entanglement, along with circuit-level fidelity measures. As part of the task of executing a quantum circuit on a device, we devise simulations, which combine expected hardware characteristics of spin-qubit devices with appropriate compilation techniques; we then analyze three different architectural choices of varying lattice sizes for bilinear arrays, under three increasingly realistic noise models. We find that if the use of a compiler is assumed, sparsely connected spin-qubit lattices can approach comparable values of our metrics to those of the most highly connected device architecture. Even more surprisingly, by incorporating crosstalk into our last noise model, we find that, as error rates for crosstalk approach realistic values, the benefits of utilizing a bilinear array with advanced connectivity vanish. Our results highlight the limitations of adding local connectivity to near-term spin-qubit devices, and can be readily adapted to other qubit technologies. The framework developed here can be used for analyzing quantum entanglement on a device before fabrication, informing experimentalists on concomitant realistic expectations.

关键词： quantum entanglement

Lightcone Bounds for quantum Circuit Mapping via Uncomplexity

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arXiv 2024年

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

Efficiently mapping quantum circuits onto hardware is an integral part of the quantum compilation process, wherein a circuit is modified in accordance with the stringent architectural demands of a quantum processor. Many techniques exist for solving the quantum circuit mapping problem, in addition to several theoretical perspectives that relate quantum circuit mapping to problems in classical computer science. This work considers a novel perspective on quantum circuit mapping, in which the routing process of a simplified circuit is viewed as a composition of quantum operations acting on density matrices representing the quantum circuit and processor. Drawing on insight from recent advances in quantum circuit complexity and information geometry, we show that a minimal SWAP-gate count for executing a quantum circuit on a device emerges via the minimization of the distance between quantum states using the quantum Jensen-Shannon divergence, which we dub the lightcone bound. Additionally, we develop a novel initial placement algorithm based on a graph similarity search that selects the partition nearest to a graph isomorphism between interaction and coupling graphs. From these two ingredients, we construct an algorithm for calculating the lightcone bound, which is directly compared alongside the IBM Qiskit compiler for over 600 realistic benchmark experiments, as well as against a brute-force method for smaller benchmarks. In our simulations, we unambiguously find that neither the brute-force method nor the Qiskit compiler surpasses our bound, signaling utility for estimating minimal overhead when realizing quantum algorithms on constrained quantum hardware. This work also constitutes the first use of quantum circuit uncomplexity to practically-relevant quantum computing. We anticipate that this method may have diverse applicability outside of the scope of quantum information science. Copyright © 2024, The Authors. All rights reserved.

关键词： quantum computers

From Designing quantum Processors to Large-Scale quantum Computing Systems

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From Designing Quantum Processors to Large-Scale Quantum Com...

Design, Automation and Test in Europe Conference and Exhibition

作者： Carmen G. Almudever Robert Wille Fabio Sebastiano Nadia Haider Eduard Alarcon Computer Engineering Department Technical University of Valencia Spain Chair for Design Automation Technical University of Munich Germany Department of Quantum and Computer Engineering Delft University of Technology The Netherlands QuTech Delft University of Technology The Netherlands Department of Electronics Engineering UPC BarcelonaTech Spain

ISBN: (数字)9783981926385

ISBN: (纸本)9798350348606

Design, simulation, analysis and verification methodologies are crucial for developing electronic circuits and systems at large. Whereas long-standing EDA software is used in the semiconductor technology, there is no counterpart for quantum computing systems yet. Although the quantum computing community started utilizing and adapting some of the already existing EDA tools, for instance, to design quantum processors and control electronics for driving the qubits, or even to solve some quantum computing design tasks, they do not fully use the expertise gained over the last decades in the field of design automation. Current intermediate-scale quantum computers have been designed in an ‘adhoc’ manner with heterogeneous methods and tools. As we are entering the large-scale era, it is timely and key to further adopt EDA methodologies and software for quantum computing. In this paper, we provide an overview on how full-stack quantum computing systems are being implemented nowadays and discuss which the main challenges are for transitioning from this current scenario to a comprehensive framework encompassing full automated system-wide architecting, design, simulation, verification, and test.

关键词： computers quantum computing Program processors quantum algorithm Qubit Noise Market research

Towards High-Fidelity Gates for the Nitrogen-Vacancy Center in Diamond

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Towards High-Fidelity Gates for the Nitrogen-Vacancy Center ...

quantum 2.0, quantum 2024 in quantum 2.0 Conference and Exhibition

作者： Yun, Jiwon Bartling, Hans P. Schymik, Kai N. van Riggelen, Margriet Enthoven, Luc A. van Ommen, Hendrik Benjamin Babaie, Masoud Sebastiano, Fabio Taminiau, Tim 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

We realize high-fidelity gates for the two-qubit system formed by NV center. Using gate set tomography, we report gate fidelities exceeding 99%, and analyze the origin of the errors. © 2024 The Author(s).

ISBN: (纸本)9781557525185

关键词： quantum optics

Neural-Network Decoders for quantum Error Correction using Surface Codes: A Space Exploration of the Hardware Cost-Performance Trade-Offs

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arXiv 2022年

作者： Overwater, Ramon W.J. Babaie, Masoud Sebastiano, Fabio QuTech Department of Quantum and Computer Engineering Delft University of Technology Delft2600 GA Netherlands

quantum Error Correction (QEC) is required in quantum computers to mitigate the effect of errors on physical qubits. When adopting a QEC scheme based on surface codes, error decoding is the most computationally expensive task in the classical electronic back-end. Decoders employing neural networks (NN) are well-suited for this task but their hardware implementation has not been presented yet. This work presents a space exploration of fully-connected feed-forward NN decoders for small distance surface codes. The goal is to optimize the neural network for high decoding performance, while keeping a minimalistic hardware implementation. This is needed to meet the tight delay constraints of real-time surface code decoding. We demonstrate that hardware based NN-decoders can achieve high decoding performance comparable to other state-of-the-art decoding algorithms whilst being well below the tight delay requirements (≈ 440 ns) of current solid-state qubit technologies for both ASIC designs ( © 2022, CC BY.

关键词： Economic and social effects

Near-Term Spin-Qubit Architecture Design via Multipartite Maximally-Entangled States

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arXiv 2024年

作者： Paraskevopoulos, Nikiforos Steinberg, Matthew Undseth, Brennan Sarkar, Aritra Vandersypen, Lieven M.K. Xue, Xiao Feld, Sebastian QuTech Delft University of Technology Delft Netherlands Quantum and Computer Engineering Department Delft University of Technology Delft Netherlands Kavli Institute of Nanoscience Delft University of Technology Delft Netherlands

The design and benchmarking of quantum computer architectures traditionally rely on practical hardware restrictions, such as gate fidelities, control, and cooling. At the theoretical and software levels, numerous approaches have been proposed for benchmarking quantum devices, ranging from, inter alia, quantum volume to randomized benchmarking. In this work, we utilize the quantum information-theoretic properties of multipartite maximally-entangled quantum states, in addition to their correspondence with quantum error correction codes, permitting us to quantify the entanglement generated on near-term bilinear spin-qubit architectures. For this aim, we introduce four metrics which ascertain the quality of genuine multipartite quantum entanglement, along with circuit-level fidelity measures. As part of the task of executing a quantum circuit on a device, we devise simulations which combine expected hardware characteristics of spin-qubit devices with appropriate compilation techniques;we then analyze three different architectural choices of varying lattice sizes for bilinear arrays, under three increasingly realistic noise models. We find that if the use of a compiler is assumed, sparsely-connected spin-qubit lattices can approach comparable values of our metrics to those of the most highly-connected device architecture. Even more surprisingly, by incorporating crosstalk into our last noise model, we find that, as error rates for crosstalk approach realistic values, the benefits of utilizing a bilinear array with advanced connectivity vanish. Our results highlight the limitations of adding local connectivity to near-term spin-qubit devices, and can be readily adapted to other qubit technologies. The framework developed here can be used for analyzing quantum entanglement on a device before fabrication, informing experimentalists on concomitant realistic expectations. Copyright © 2024, The Authors. All rights reserved.

关键词： quantum entanglement

Cryogenic Characterization of Low-Frequency Noise in 40-nm CMOS

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arXiv 2024年

作者： Kiene, Gerd Ilik, Sadık Mastrodomenico, Luigi Babaie, Masoud Sebastiano, Fabio Department of Quantum and Computer Engineering Delft University of Technology Delft2628 CJ Netherlands Qutech Delft2628 CJ Netherlands Department of Microelectronics Delft University of Technology Delft2628 CD Netherlands

This paper presents an extensive characterization of the low-frequency noise (LFN) at room temperature (RT) and cryogenic temperature (4.2 K) of 40-nm bulk-CMOS transistors. The noise is measured over a wide range of bias conditions and geometries to generate a comprehensive overview of LFN in this technology. While the RT results are in-line with the literature and the foundry models, the cryogenic behavior diverges in many aspects. These deviations include changes with respect to RT in magnitude and bias dependence that are conditional on transistor type and geometry, and even an additional systematic Lorentzian feature that is common among individual devices. Furthermore, we find the scaling of the average LFN with the area and its variability to be similar between RT and 4.2 K, with the cryogenic scaling reported systematically for the first time. The findings suggest that, as no consistent decrease of LFN at lower temperatures is observed while the white noise is reduced, the impact of LFN for precision analog design at cryogenic temperatures gains a more predominant role. © 2024, CC BY.

关键词： Cryogenics