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Gao H, Kong ZZ, Zhang P, Luo Y, Su H, Liu XF, Wang GL, Wang JY, Xu HQ. Gate-defined quantum point contacts in a germanium quantum well. NANOSCALE 2024; 16:10333-10339. [PMID: 38738596 DOI: 10.1039/d4nr00712c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2024]
Abstract
We report an experimental study of quantum point contacts defined in a high-quality strained germanium quantum well with layered electric gates. At a zero magnetic field, we observed quantized conductance plateaus in units of 2e2/h. Bias-spectroscopy measurements reveal that the energy spacing between successive one-dimensional subbands ranges from 1.5 to 5 meV as a consequence of the small effective mass of the holes and the narrow gate constrictions. At finite magnetic fields perpendicular to the device plane, the edges of the conductance plateaus get split due to the Zeeman effect and Landé g factors were estimated to be ∼6.6 for the holes in the germanium quantum well. We demonstrate that all quantum point contacts in the same device have comparable performances, indicating a reliable and reproducible device fabrication process. Thus, our work lays a foundation for investigating multiple forefronts of physics in germanium-based quantum devices that require quantum point contacts as building blocks.
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Affiliation(s)
- Han Gao
- Beijing Key Laboratory of Quantum Devices, Key Laboratory for the Physics and Chemistry of Nanodevices, and School of Electronics, Peking University, Beijing 100871, China.
| | - Zhen-Zhen Kong
- Key Laboratory of Microelectronics Devices & Integrated Technology, Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029, China.
| | - Po Zhang
- Beijing Academy of Quantum Information Sciences, Beijing 100193, China.
| | - Yi Luo
- Beijing Key Laboratory of Quantum Devices, Key Laboratory for the Physics and Chemistry of Nanodevices, and School of Electronics, Peking University, Beijing 100871, China.
- Institute of Condensed Matter and Material Physics, School of Physics, Peking University, Beijing 100871, China
| | - Haitian Su
- Beijing Key Laboratory of Quantum Devices, Key Laboratory for the Physics and Chemistry of Nanodevices, and School of Electronics, Peking University, Beijing 100871, China.
- Institute of Condensed Matter and Material Physics, School of Physics, Peking University, Beijing 100871, China
| | - Xiao-Fei Liu
- Beijing Academy of Quantum Information Sciences, Beijing 100193, China.
| | - Gui-Lei Wang
- Key Laboratory of Microelectronics Devices & Integrated Technology, Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029, China.
- Hefei National Laboratory, University of Science and Technology of China, Hefei, Anhui 230088, China
- Beijing Superstring Academy of Memory Technology, Beijing 100176, China
| | - Ji-Yin Wang
- Beijing Academy of Quantum Information Sciences, Beijing 100193, China.
| | - H Q Xu
- Beijing Key Laboratory of Quantum Devices, Key Laboratory for the Physics and Chemistry of Nanodevices, and School of Electronics, Peking University, Beijing 100871, China.
- Beijing Academy of Quantum Information Sciences, Beijing 100193, China.
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2
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Hendrickx NW, Massai L, Mergenthaler M, Schupp FJ, Paredes S, Bedell SW, Salis G, Fuhrer A. Sweet-spot operation of a germanium hole spin qubit with highly anisotropic noise sensitivity. NATURE MATERIALS 2024:10.1038/s41563-024-01857-5. [PMID: 38760518 DOI: 10.1038/s41563-024-01857-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/22/2023] [Accepted: 03/11/2024] [Indexed: 05/19/2024]
Abstract
Spin qubits defined by valence band hole states are attractive for quantum information processing due to their inherent coupling to electric fields, enabling fast and scalable qubit control. Heavy holes in germanium are particularly promising, with recent demonstrations of fast and high-fidelity qubit operations. However, the mechanisms and anisotropies that underlie qubit driving and decoherence remain mostly unclear. Here we report the highly anisotropic heavy-hole g-tensor and its dependence on electric fields, revealing how qubit driving and decoherence originate from electric modulations of the g-tensor. Furthermore, we confirm the predicted Ising-type hyperfine interaction and show that qubit coherence is ultimately limited by 1/f charge noise, where f is the frequency. Finally, operating the qubit at low magnetic field, we measure a dephasing time ofT 2 * = 17.6 μs, maintaining single-qubit gate fidelities well above 99% even at elevated temperatures of T > 1 K. This understanding of qubit driving and decoherence mechanisms is key towards realizing scalable and highly coherent hole qubit arrays.
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Affiliation(s)
- N W Hendrickx
- IBM Research Europe - Zurich, Rüschlikon, Switzerland.
| | - L Massai
- IBM Research Europe - Zurich, Rüschlikon, Switzerland
| | | | - F J Schupp
- IBM Research Europe - Zurich, Rüschlikon, Switzerland
| | - S Paredes
- IBM Research Europe - Zurich, Rüschlikon, Switzerland
| | - S W Bedell
- IBM Quantum, T.J. Watson Research Center, Yorktown Heights, NY, USA
| | - G Salis
- IBM Research Europe - Zurich, Rüschlikon, Switzerland
| | - A Fuhrer
- IBM Research Europe - Zurich, Rüschlikon, Switzerland.
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3
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Cookmeyer T, Das Sarma S. Engineering the Kitaev Spin Liquid in a Quantum Dot System. PHYSICAL REVIEW LETTERS 2024; 132:186501. [PMID: 38759190 DOI: 10.1103/physrevlett.132.186501] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2023] [Revised: 02/22/2024] [Accepted: 03/29/2024] [Indexed: 05/19/2024]
Abstract
The Kitaev model on a honeycomb lattice may provide a robust topological quantum memory platform, but finding a material that realizes the unique spin-liquid phase remains a considerable challenge. We demonstrate that an effective Kitaev Hamiltonian can arise from a half-filled Fermi-Hubbard Hamiltonian where each site can experience a magnetic field in a different direction. As such, we provide a method for realizing the Kitaev spin liquid on a single hexagonal plaquette made up of 12 quantum dots. Despite the small system size, there are clear signatures of the Kitaev spin-liquid ground state, and there is a range of parameters where these signatures are predicted, allowing a potential platform where Kitaev spin-liquid physics can be explored experimentally in quantum dot plaquettes.
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Affiliation(s)
- Tessa Cookmeyer
- Kavli Institute for Theoretical Physics, University of California, Santa Barbara, California 93106-4030, USA
| | - Sankar Das Sarma
- Kavli Institute for Theoretical Physics, University of California, Santa Barbara, California 93106-4030, USA
- Condensed Matter Theory Center and Joint Quantum Institute, Department of Physics, University of Maryland, College Park, Maryland 20742-4111, USA
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4
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Neyens S, Zietz OK, Watson TF, Luthi F, Nethwewala A, George HC, Henry E, Islam M, Wagner AJ, Borjans F, Connors EJ, Corrigan J, Curry MJ, Keith D, Kotlyar R, Lampert LF, Mądzik MT, Millard K, Mohiyaddin FA, Pellerano S, Pillarisetty R, Ramsey M, Savytskyy R, Schaal S, Zheng G, Ziegler J, Bishop NC, Bojarski S, Roberts J, Clarke JS. Probing single electrons across 300-mm spin qubit wafers. Nature 2024; 629:80-85. [PMID: 38693414 PMCID: PMC11062914 DOI: 10.1038/s41586-024-07275-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2023] [Accepted: 03/05/2024] [Indexed: 05/03/2024]
Abstract
Building a fault-tolerant quantum computer will require vast numbers of physical qubits. For qubit technologies based on solid-state electronic devices1-3, integrating millions of qubits in a single processor will require device fabrication to reach a scale comparable to that of the modern complementary metal-oxide-semiconductor (CMOS) industry. Equally important, the scale of cryogenic device testing must keep pace to enable efficient device screening and to improve statistical metrics such as qubit yield and voltage variation. Spin qubits1,4,5 based on electrons in Si have shown impressive control fidelities6-9 but have historically been challenged by yield and process variation10-12. Here we present a testing process using a cryogenic 300-mm wafer prober13 to collect high-volume data on the performance of hundreds of industry-manufactured spin qubit devices at 1.6 K. This testing method provides fast feedback to enable optimization of the CMOS-compatible fabrication process, leading to high yield and low process variation. Using this system, we automate measurements of the operating point of spin qubits and investigate the transitions of single electrons across full wafers. We analyse the random variation in single-electron operating voltages and find that the optimized fabrication process leads to low levels of disorder at the 300-mm scale. Together, these results demonstrate the advances that can be achieved through the application of CMOS-industry techniques to the fabrication and measurement of spin qubit devices.
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5
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Zhang Y, Oberg CP, Hu Y, Xu H, Yan M, Scholes GD, Wang M. Molecular and Supramolecular Materials: From Light-Harvesting to Quantum Information Science and Technology. J Phys Chem Lett 2024:3294-3316. [PMID: 38497707 DOI: 10.1021/acs.jpclett.4c00264] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/19/2024]
Abstract
The past two decades have witnessed immense advances in quantum information technology (QIT), benefited by advances in physics, chemistry, biology, and materials science and engineering. It is intriguing to consider whether these diverse molecular and supramolecular structures and materials, partially inspired by quantum effects as observed in sophisticated biological systems such as light-harvesting complexes in photosynthesis and the magnetic compass of migratory birds, might play a role in future QIT. If so, how? Herein, we review materials and specify the relationship between structures and quantum properties, and we identify the challenges and limitations that have restricted the intersection of QIT and chemical materials. Examples are broken down into two categories: materials for quantum sensing where nonclassical function is observed on the molecular scale and systems where nonclassical phenomena are present due to intermolecular interactions. We discuss challenges for materials chemistry and make comparisons to related systems found in nature. We conclude that if chemical materials become relevant for QIT, they will enable quite new kinds of properties and functions.
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Affiliation(s)
- Yipeng Zhang
- School of Science and Engineering, The Chinese University of Hong Kong, Shenzhen, Guangdong 518172, P. R. China
| | - Catrina P Oberg
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Yue Hu
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Hongxue Xu
- School of Science and Engineering, The Chinese University of Hong Kong, Shenzhen, Guangdong 518172, P. R. China
| | - Mengwen Yan
- School of Science and Engineering, The Chinese University of Hong Kong, Shenzhen, Guangdong 518172, P. R. China
| | - Gregory D Scholes
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Mingfeng Wang
- School of Science and Engineering, The Chinese University of Hong Kong, Shenzhen, Guangdong 518172, P. R. China
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6
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John V, Borsoi F, György Z, Wang CA, Széchenyi G, van Riggelen-Doelman F, Lawrie WIL, Hendrickx NW, Sammak A, Scappucci G, Pályi A, Veldhorst M. Bichromatic Rabi Control of Semiconductor Qubits. PHYSICAL REVIEW LETTERS 2024; 132:067001. [PMID: 38394602 DOI: 10.1103/physrevlett.132.067001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/04/2023] [Accepted: 10/20/2023] [Indexed: 02/25/2024]
Abstract
Electrically driven spin resonance is a powerful technique for controlling semiconductor spin qubits. However, it faces challenges in qubit addressability and off-resonance driving in larger systems. We demonstrate coherent bichromatic Rabi control of quantum dot hole spin qubits, offering a spatially selective approach for large qubit arrays. By applying simultaneous microwave bursts to different gate electrodes, we observe multichromatic resonance lines and resonance anticrossings that are caused by the ac Stark shift. Our theoretical framework aligns with experimental data, highlighting interdot motion as the dominant mechanism for bichromatic driving.
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Affiliation(s)
- Valentin John
- QuTech and Kavli Institute of Nanoscience, Delft University of Technology, P.O. Box 5046, 2600 GA Delft, Netherlands
| | - Francesco Borsoi
- QuTech and Kavli Institute of Nanoscience, Delft University of Technology, P.O. Box 5046, 2600 GA Delft, Netherlands
| | - Zoltán György
- ELTE Eötvös Loránd University, Institute of Physics, H-1117 Budapest, Hungary
| | - Chien-An Wang
- QuTech and Kavli Institute of Nanoscience, Delft University of Technology, P.O. Box 5046, 2600 GA Delft, Netherlands
| | - Gábor Széchenyi
- ELTE Eötvös Loránd University, Institute of Physics, H-1117 Budapest, Hungary
| | - Floor van Riggelen-Doelman
- QuTech and Kavli Institute of Nanoscience, Delft University of Technology, P.O. Box 5046, 2600 GA Delft, Netherlands
| | - William I L Lawrie
- QuTech and Kavli Institute of Nanoscience, Delft University of Technology, P.O. Box 5046, 2600 GA Delft, Netherlands
| | - Nico W Hendrickx
- QuTech and Kavli Institute of Nanoscience, Delft University of Technology, P.O. Box 5046, 2600 GA Delft, Netherlands
| | - Amir Sammak
- QuTech and Netherlands Organisation for Applied Scientific Research (TNO), Stieltjesweg 1, 2628 CK Delft, Netherlands
| | - Giordano Scappucci
- QuTech and Kavli Institute of Nanoscience, Delft University of Technology, P.O. Box 5046, 2600 GA Delft, Netherlands
| | - András Pályi
- Department of Theoretical Physics, Institute of Physics, Budapest University of Technology and Economics, Műegyetem rakpart 3, H-1111 Budapest, Hungary
- MTA-BME Quantum Dynamics and Correlations Research Group, Budapest University of Technology and Economics, Műegyetem rakpart 3, H-1111 Budapest, Hungary
| | - Menno Veldhorst
- QuTech and Kavli Institute of Nanoscience, Delft University of Technology, P.O. Box 5046, 2600 GA Delft, Netherlands
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7
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Meyer M, Déprez C, Meijer IN, Unseld FK, Karwal S, Sammak A, Scappucci G, Vandersypen LMK, Veldhorst M. Single-Electron Occupation in Quantum Dot Arrays at Selectable Plunger Gate Voltage. NANO LETTERS 2023; 23:11593-11600. [PMID: 38091376 PMCID: PMC10755753 DOI: 10.1021/acs.nanolett.3c03349] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2023] [Revised: 12/06/2023] [Accepted: 12/07/2023] [Indexed: 12/28/2023]
Abstract
The small footprint of semiconductor qubits is favorable for scalable quantum computing. However, their size also makes them sensitive to their local environment and variations in the gate structure. Currently, each device requires tailored gate voltages to confine a single charge per quantum dot, clearly challenging scalability. Here, we tune these gate voltages and equalize them solely through the temporary application of stress voltages. In a double quantum dot, we reach a stable (1,1) charge state at identical and predetermined plunger gate voltage and for various interdot couplings. Applying our findings, we tune a 2 × 2 quadruple quantum dot such that the (1,1,1,1) charge state is reached when all plunger gates are set to 1 V. The ability to define required gate voltages may relax requirements on control electronics and operations for spin qubit devices, providing means to advance quantum hardware.
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Affiliation(s)
- Marcel Meyer
- QuTech
and Kavli Institute of Nanoscience, Delft
University of Technology, PO Box 5046, 2600 GA Delft, The
Netherlands
| | - Corentin Déprez
- QuTech
and Kavli Institute of Nanoscience, Delft
University of Technology, PO Box 5046, 2600 GA Delft, The
Netherlands
| | - Ilja N. Meijer
- QuTech
and Kavli Institute of Nanoscience, Delft
University of Technology, PO Box 5046, 2600 GA Delft, The
Netherlands
| | - Florian K. Unseld
- QuTech
and Kavli Institute of Nanoscience, Delft
University of Technology, PO Box 5046, 2600 GA Delft, The
Netherlands
| | - Saurabh Karwal
- QuTech
and Netherlands Organisation for Applied Scientific Research (TNO), PO Box 155, 2600 AD Delft, The Netherlands
| | - Amir Sammak
- QuTech
and Netherlands Organisation for Applied Scientific Research (TNO), PO Box 155, 2600 AD Delft, The Netherlands
| | - Giordano Scappucci
- QuTech
and Kavli Institute of Nanoscience, Delft
University of Technology, PO Box 5046, 2600 GA Delft, The
Netherlands
| | - Lieven M. K. Vandersypen
- QuTech
and Kavli Institute of Nanoscience, Delft
University of Technology, PO Box 5046, 2600 GA Delft, The
Netherlands
| | - Menno Veldhorst
- QuTech
and Kavli Institute of Nanoscience, Delft
University of Technology, PO Box 5046, 2600 GA Delft, The
Netherlands
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8
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Olšteins D, Nagda G, Carrad DJ, Beznasyuk DV, Petersen CEN, Martí-Sánchez S, Arbiol J, Jespersen TS. Cryogenic multiplexing using selective area grown nanowires. Nat Commun 2023; 14:7738. [PMID: 38007553 PMCID: PMC10676361 DOI: 10.1038/s41467-023-43551-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2023] [Accepted: 11/13/2023] [Indexed: 11/27/2023] Open
Abstract
Bottom-up grown nanomaterials play an integral role in the development of quantum technologies but are often challenging to characterise on large scales. Here, we harness selective area growth of semiconductor nanowires to demonstrate large-scale integrated circuits and characterisation of large numbers of quantum devices. The circuit consisted of 512 quantum devices embedded within multiplexer/demultiplexer pairs, incorporating thousands of interconnected selective area growth nanowires operating under deep cryogenic conditions. Multiplexers enable a range of new strategies in quantum device research and scaling by increasing the device count while limiting the number of connections between room-temperature control electronics and the cryogenic samples. As an example of this potential we perform a statistical characterization of large arrays of identical quantum dots thus establishing the feasibility of applying cross-bar gating strategies for efficient scaling of future selective area growth quantum circuits. More broadly, the ability to systematically characterise large numbers of devices provides new levels of statistical certainty to materials/device development.
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Affiliation(s)
- Dāgs Olšteins
- Center For Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100, Copenhagen, Denmark
- Department of Energy Conversion and Storage, Technical University of Denmark, 2800, Kongens Lyngby, Denmark
| | - Gunjan Nagda
- Center For Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100, Copenhagen, Denmark
| | - Damon J Carrad
- Department of Energy Conversion and Storage, Technical University of Denmark, 2800, Kongens Lyngby, Denmark
| | - Daria V Beznasyuk
- Department of Energy Conversion and Storage, Technical University of Denmark, 2800, Kongens Lyngby, Denmark
| | - Christian E N Petersen
- Department of Energy Conversion and Storage, Technical University of Denmark, 2800, Kongens Lyngby, Denmark
| | - Sara Martí-Sánchez
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB, Bellaterra, Barcelona, Catalonia, Spain
| | - Jordi Arbiol
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB, Bellaterra, Barcelona, Catalonia, Spain
- ICREA, Passeig de Lluís Companys 23, 08010, Barcelona, Catalonia, Spain
| | - Thomas S Jespersen
- Center For Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100, Copenhagen, Denmark.
- Department of Energy Conversion and Storage, Technical University of Denmark, 2800, Kongens Lyngby, Denmark.
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