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Kuroyama K, Kwoen J, Arakawa Y, Hirakawa K. Coherent Interaction of a Few-Electron Quantum Dot with a Terahertz Optical Resonator. PHYSICAL REVIEW LETTERS 2024; 132:066901. [PMID: 38394566 DOI: 10.1103/physrevlett.132.066901] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2022] [Revised: 08/07/2023] [Accepted: 12/06/2023] [Indexed: 02/25/2024]
Abstract
We have investigated light-matter hybrid excitations in a quantum dot (QD) THz resonator coupled system. We fabricate a gate-defined QD near a THz split-ring resonator (SRR) by using a AlGaAs/GaAs two-dimensional electron system. By illuminating the system with THz radiation, the QD shows a current change whose spectrum exhibits coherent coupling between the electrons in the QD and the SRR as well as coupling between the two-dimensional electron system and the SRR. The latter coupling enters the ultrastrong coupling regime and the electron excitation in the QD also exhibits coherent coupling with the SRR with the remarkably large coupling constant, despite the fact that only a few electrons reside in the QD.
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Affiliation(s)
- Kazuyuki Kuroyama
- Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan
| | - Jinkwan Kwoen
- Institute for Nano Quantum Information Electronics, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan
| | - Yasuhiko Arakawa
- Institute for Nano Quantum Information Electronics, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan
| | - Kazuhiko Hirakawa
- Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan
- Institute for Nano Quantum Information Electronics, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan
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2
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Kuroyama K, Kwoen J, Arakawa Y, Hirakawa K. Electrical Detection of Ultrastrong Coherent Interaction between Terahertz Fields and Electrons Using Quantum Point Contacts. NANO LETTERS 2023; 23:11402-11408. [PMID: 37910773 DOI: 10.1021/acs.nanolett.3c02272] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/03/2023]
Abstract
Light-matter interaction in the ultrastrong coupling regime is attracting considerable attention owing to its applications to coherent control of material properties by a vacuum fluctuation field. However, electrical access to such an ultrastrongly coupled system is very challenging. In this work, we have fabricated a gate-defined quantum point contact (QPC) near the gap of a terahertz (THz) split-ring resonator (SRR) fabricated on a GaAs two-dimensional (2D) electron system. By illuminating the system with external THz radiation, the QPC shows a photocurrent spectrum which exhibits significant anticrossing that arises from coupling between the cyclotron resonance of the 2D electrons and the SRR. The observed photocurrent signal can be explained by energy-selective transmission/reflection of the quantum Hall edge channels at the QPC. Furthermore, at the same gate voltage and magnetic field conditions under which the anticrossing signal was observed, the QPC exhibits anomalous conductance modulation even in the dark environment.
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Affiliation(s)
- Kazuyuki Kuroyama
- Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan
| | - Jinkwan Kwoen
- Institute for Nano Quantum Information Electronics, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan
| | - Yasuhiko Arakawa
- Institute for Nano Quantum Information Electronics, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan
| | - Kazuhiko Hirakawa
- Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan
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3
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Hecker K, Banszerus L, Schäpers A, Möller S, Peters A, Icking E, Watanabe K, Taniguchi T, Volk C, Stampfer C. Coherent charge oscillations in a bilayer graphene double quantum dot. Nat Commun 2023; 14:7911. [PMID: 38036517 PMCID: PMC10689829 DOI: 10.1038/s41467-023-43541-3] [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: 03/14/2023] [Accepted: 11/13/2023] [Indexed: 12/02/2023] Open
Abstract
The coherent dynamics of a quantum mechanical two-level system passing through an anti-crossing of two energy levels can give rise to Landau-Zener-Stückelberg-Majorana (LZSM) interference. LZSM interference spectroscopy has proven to be a fruitful tool to investigate charge noise and charge decoherence in semiconductor quantum dots (QDs). Recently, bilayer graphene has developed as a promising platform to host highly tunable QDs potentially useful for hosting spin and valley qubits. So far, in this system no coherent oscillations have been observed and little is known about charge noise in this material. Here, we report coherent charge oscillations and [Formula: see text] charge decoherence times in a bilayer graphene double QD. The charge decoherence times are measured independently using LZSM interference and photon assisted tunneling. Both techniques yield [Formula: see text] average values in the range of 400-500 ps. The observation of charge coherence allows to study the origin and spectral distribution of charge noise in future experiments.
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Affiliation(s)
- K Hecker
- JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52074, Aachen, Germany.
- Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, 52425, Jülich, Germany.
| | - L Banszerus
- JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52074, Aachen, Germany
- Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, 52425, Jülich, Germany
| | - A Schäpers
- JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52074, Aachen, Germany
| | - S Möller
- JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52074, Aachen, Germany
- Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, 52425, Jülich, Germany
| | - A Peters
- JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52074, Aachen, Germany
| | - E Icking
- JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52074, Aachen, Germany
- Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, 52425, Jülich, Germany
| | - K Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - T Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - C Volk
- JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52074, Aachen, Germany
- Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, 52425, Jülich, Germany
| | - C Stampfer
- JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52074, Aachen, Germany
- Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, 52425, Jülich, Germany
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A Robust Protocol for Entropy Measurement in Mesoscopic Circuits. ENTROPY 2022; 24:e24030417. [PMID: 35327927 PMCID: PMC8948648 DOI: 10.3390/e24030417] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/24/2022] [Revised: 03/11/2022] [Accepted: 03/13/2022] [Indexed: 02/01/2023]
Abstract
Previous measurements utilizing Maxwell relations to measure change in entropy, S, demonstrated remarkable accuracy in measuring the spin-1/2 entropy of electrons in a weakly coupled quantum dot. However, these previous measurements relied upon prior knowledge of the charge transition lineshape. This had the benefit of making the quantitative determination of entropy independent of scale factors in the measurement itself but at the cost of limiting the applicability of the approach to simple systems. To measure the entropy of more exotic mesoscopic systems, a more flexible analysis technique may be employed; however, doing so requires a precise calibration of the measurement. Here, we give details on the necessary improvements made to the original experimental approach and highlight some of the common challenges (along with strategies to overcome them) that other groups may face when attempting this type of measurement.
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Kranz L, Gorman SK, Thorgrimsson B, He Y, Keith D, Keizer JG, Simmons MY. Exploiting a Single-Crystal Environment to Minimize the Charge Noise on Qubits in Silicon. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2020; 32:e2003361. [PMID: 32830388 DOI: 10.1002/adma.202003361] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2020] [Revised: 07/22/2020] [Accepted: 07/27/2020] [Indexed: 06/11/2023]
Abstract
Electron spins in silicon offer a competitive, scalable quantum-computing platform with excellent single-qubit properties. However, the two-qubit gate fidelities achieved so far have fallen short of the 99% threshold required for large-scale error-corrected quantum computing architectures. In the past few years, there has been a growing realization that the critical obstacle in meeting this threshold in semiconductor qubits is charge noise arising from the qubit environment. In this work, a notably low level of charge noise of S0 = 0.0088 ± 0.0004 μeV2 Hz-1 is demonstrated using atom qubits in crystalline silicon, achieved by separating the qubits from surfaces and interface states. The charge noise is measured using both a single electron transistor and an exchange-coupled qubit pair that collectively provide a consistent charge noise spectrum over four frequency decades, with the noise level S0 being an order of magnitude lower than previously reported. Low-frequency detuning noise, set by the total measurement time, is shown to be the dominant dephasing source of two-qubit exchange oscillations. With recent advances in fast (≈μs) single-shot readout, it is shown that by reducing the total measurement time to ≈1 s, 99.99% two-qubit S W A P gate fidelities can be achieved in single-crystal atom qubits in silicon.
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Affiliation(s)
- Ludwik Kranz
- Centre of Excellence for Quantum Computation and Communication Technology, School of Physics, University of New South Wales, Sydney, NSW, 2052, Australia
- Silicon Quantum Computing Pty Ltd., Level 2, Newton Building, UNSW Sydney, Kensington, NSW, 2052, Australia
| | - Samuel Keith Gorman
- Centre of Excellence for Quantum Computation and Communication Technology, School of Physics, University of New South Wales, Sydney, NSW, 2052, Australia
- Silicon Quantum Computing Pty Ltd., Level 2, Newton Building, UNSW Sydney, Kensington, NSW, 2052, Australia
| | - Brandur Thorgrimsson
- Centre of Excellence for Quantum Computation and Communication Technology, School of Physics, University of New South Wales, Sydney, NSW, 2052, Australia
- Silicon Quantum Computing Pty Ltd., Level 2, Newton Building, UNSW Sydney, Kensington, NSW, 2052, Australia
| | - Yu He
- Centre of Excellence for Quantum Computation and Communication Technology, School of Physics, University of New South Wales, Sydney, NSW, 2052, Australia
| | - Daniel Keith
- Centre of Excellence for Quantum Computation and Communication Technology, School of Physics, University of New South Wales, Sydney, NSW, 2052, Australia
| | - Joris Gerhard Keizer
- Centre of Excellence for Quantum Computation and Communication Technology, School of Physics, University of New South Wales, Sydney, NSW, 2052, Australia
- Silicon Quantum Computing Pty Ltd., Level 2, Newton Building, UNSW Sydney, Kensington, NSW, 2052, Australia
| | - Michelle Yvonne Simmons
- Centre of Excellence for Quantum Computation and Communication Technology, School of Physics, University of New South Wales, Sydney, NSW, 2052, Australia
- Silicon Quantum Computing Pty Ltd., Level 2, Newton Building, UNSW Sydney, Kensington, NSW, 2052, Australia
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6
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Russ M, Burkard G. Three-electron spin qubits. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:393001. [PMID: 28562367 DOI: 10.1088/1361-648x/aa761f] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The goal of this article is to review the progress of three-electron spin qubits from their inception to the state of the art. We direct the main focus towards the exchange-only qubit (Bacon et al 2000 Phys. Rev. Lett. 85 1758-61, DiVincenzo et al 2000 Nature 408 339) and its derived versions, e.g. the resonant exchange (RX) qubit, but we also discuss other qubit implementations using three electron spins. For each three-spin qubit we describe the qubit model, the envisioned physical realization, the implementations of single-qubit operations, as well as the read-out and initialization schemes. Two-qubit gates and decoherence properties are discussed for the RX qubit and the exchange-only qubit, thereby completing the list of requirements for quantum computation for a viable candidate qubit implementation. We start by describing the full system of three electrons in a triple quantum dot, then discuss the charge-stability diagram, restricting ourselves to the relevant subsystem, introduce the qubit states, and discuss important transitions to other charge states (Russ et al 2016 Phys. Rev. B 94 165411). Introducing the various qubit implementations, we begin with the exchange-only qubit (DiVincenzo et al 2000 Nature 408 339, Laird et al 2010 Phys. Rev. B 82 075403), followed by the RX qubit (Medford et al 2013 Phys. Rev. Lett. 111 050501, Taylor et al 2013 Phys. Rev. Lett. 111 050502), the spin-charge qubit (Kyriakidis and Burkard 2007 Phys. Rev. B 75 115324), and the hybrid qubit (Shi et al 2012 Phys. Rev. Lett. 108 140503, Koh et al 2012 Phys. Rev. Lett. 109 250503, Cao et al 2016 Phys. Rev. Lett. 116 086801, Thorgrimsson et al 2016 arXiv:1611.04945). The main focus will be on the exchange-only qubit and its modification, the RX qubit, whose single-qubit operations are realized by driving the qubit at its resonant frequency in the microwave range similar to electron spin resonance. Two different types of two-qubit operations are presented for the exchange-only qubits which can be divided into short-ranged and long-ranged interactions. Both of these interaction types are expected to be necessary in a large-scale quantum computer. The short-ranged interactions use the exchange coupling by placing qubits next to each other and applying exchange-pulses (DiVincenzo et al 2000 Nature 408 339, Fong and Wandzura 2011 Quantum Inf. Comput. 11 1003, Setiawan et al 2014 Phys. Rev. B 89 085314, Zeuch et al 2014 Phys. Rev. B 90 045306, Doherty and Wardrop 2013 Phys. Rev. Lett. 111 050503, Shim and Tahan 2016 Phys. Rev. B 93 121410), while the long-ranged interactions use the photons of a superconducting microwave cavity as a mediator in order to couple two qubits over long distances (Russ and Burkard 2015 Phys. Rev. B 92 205412, Srinivasa et al 2016 Phys. Rev. B 94 205421). The nature of the three-electron qubit states each having the same total spin and total spin in z-direction (same Zeeman energy) provides a natural protection against several sources of noise (DiVincenzo et al 2000 Nature 408 339, Taylor et al 2013 Phys. Rev. Lett. 111 050502, Kempe et al 2001 Phys. Rev. A 63 042307, Russ and Burkard 2015 Phys. Rev. B 91 235411). The price to pay for this advantage is an increase in gate complexity. We also take into account the decoherence of the qubit through the influence of magnetic noise (Ladd 2012 Phys. Rev. B 86 125408, Mehl and DiVincenzo 2013 Phys. Rev. B 87 195309, Hung et al 2014 Phys. Rev. B 90 045308), in particular dephasing due to the presence of nuclear spins, as well as dephasing due to charge noise (Medford et al 2013 Phys. Rev. Lett. 111 050501, Taylor et al 2013 Phys. Rev. Lett. 111 050502, Shim and Tahan 2016 Phys. Rev. B 93 121410, Russ and Burkard 2015 Phys. Rev. B 91 235411, Fei et al 2015 Phys. Rev. B 91 205434), fluctuations of the energy levels on each dot due to noisy gate voltages or the environment. Several techniques are discussed which partly decouple the qubit from magnetic noise (Setiawan et al 2014 Phys. Rev. B 89 085314, West and Fong 2012 New J. Phys. 14 083002, Rohling and Burkard 2016 Phys. Rev. B 93 205434) while for charge noise it is shown that it is favorable to operate the qubit on the so-called '(double) sweet spots' (Taylor et al 2013 Phys. Rev. Lett. 111 050502, Shim and Tahan 2016 Phys. Rev. B 93 121410, Russ and Burkard 2015 Phys. Rev. B 91 235411, Fei et al 2015 Phys. Rev. B 91 205434, Malinowski et al 2017 arXiv: 1704.01298), which are least susceptible to noise, thus providing a longer lifetime of the qubit.
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Affiliation(s)
- Maximilian Russ
- Department of Physics, University of Konstanz, D-78457 Konstanz, Germany
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7
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Shamim S, Weber B, Thompson DW, Simmons MY, Ghosh A. Ultralow-Noise Atomic-Scale Structures for Quantum Circuitry in Silicon. NANO LETTERS 2016; 16:5779-5784. [PMID: 27525390 DOI: 10.1021/acs.nanolett.6b02513] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The atomically precise doping of silicon with phosphorus (Si:P) using scanning tunneling microscopy (STM) promises ultimate miniaturization of field effect transistors. The one-dimensional (1D) Si:P nanowires are of particular interest, retaining exceptional conductivity down to the atomic scale, and are predicted as interconnects for a scalable silicon-based quantum computer. Here, we show that ultrathin Si:P nanowires form one of the most-stable electrical conductors, with the phenomenological Hooge parameter of low-frequency noise being as low as ≈10(-8) at 4.2 K, nearly 3 orders of magnitude lower than even carbon-nanotube-based 1D conductors. A in-built isolation from the surface charge fluctuations due to encapsulation of the wires within the epitaxial Si matrix is the dominant cause for the observed suppression of noise. Apart from quantum information technology, our results confirm the promising prospects for precision-doped Si:P structures in atomic-scale circuitry for the 11 nm technology node and beyond.
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Affiliation(s)
- Saquib Shamim
- Department of Physics, Indian Institute of Science , Bangalore 560 012, India
| | - Bent Weber
- Centre for Quantum Computation and Communication Technology, University of New South Wales , Sydney, NSW 2052, Australia
- School of Physics and Astronomy, Monash University , Melbourne, VIC 3800, Australia
| | - Daniel W Thompson
- Centre for Quantum Computation and Communication Technology, University of New South Wales , Sydney, NSW 2052, Australia
| | - Michelle Y Simmons
- Centre for Quantum Computation and Communication Technology, University of New South Wales , Sydney, NSW 2052, Australia
| | - Arindam Ghosh
- Department of Physics, Indian Institute of Science , Bangalore 560 012, India
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Martins F, Malinowski FK, Nissen PD, Barnes E, Fallahi S, Gardner GC, Manfra MJ, Marcus CM, Kuemmeth F. Noise Suppression Using Symmetric Exchange Gates in Spin Qubits. PHYSICAL REVIEW LETTERS 2016; 116:116801. [PMID: 27035316 DOI: 10.1103/physrevlett.116.116801] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2015] [Indexed: 06/05/2023]
Abstract
We demonstrate a substantial improvement in the spin-exchange gate using symmetric control instead of conventional detuning in GaAs spin qubits, up to a factor of six increase in the quality factor of the gate. For symmetric operation, nanosecond voltage pulses are applied to the barrier that controls the interdot potential between quantum dots, modulating the exchange interaction while maintaining symmetry between the dots. Excellent agreement is found with a model that separately includes electrical and nuclear noise sources for both detuning and symmetric gating schemes. Unlike exchange control via detuning, the decoherence of symmetric exchange rotations is dominated by rotation-axis fluctuations due to nuclear field noise rather than direct exchange noise.
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Affiliation(s)
- Frederico Martins
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Filip K Malinowski
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Peter D Nissen
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Edwin Barnes
- Department of Physics, Virginia Tech, Blacksburg, Virginia 24061, USA
- Condensed Matter Theory Center and Joint Quantum Institute, Department of Physics, University of Maryland, College Park, Maryland 20742-4111, USA
| | - Saeed Fallahi
- Department of Physics and Astronomy and Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, USA
| | - Geoffrey C Gardner
- School of Materials Engineering and Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, USA
| | - Michael J Manfra
- Department of Physics and Astronomy and Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, USA
- School of Materials Engineering and Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, USA
- School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907, USA
| | - Charles M Marcus
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Ferdinand Kuemmeth
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark
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9
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Beukman AJA, Qu F, West KW, Pfeiffer LN, Kouwenhoven LP. A Noninvasive Method for Nanoscale Electrostatic Gating of Pristine Materials. NANO LETTERS 2015; 15:6883-6888. [PMID: 26375825 DOI: 10.1021/acs.nanolett.5b02800] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Electrostatic gating is essential for defining and control of semiconducting devices. However, nanofabrication processes required for depositing gates inevitably degrade the pristine quality of the material of interest. Examples of materials that suffer from such degradation include ultrahigh mobility GaAs/AlGaAs two-dimensional electron gases (2DEGs), graphene, topological insulators, and nanowires. To preserve the pristine material properties, we have developed a flip-chip setup where gates are separated from the material by a vacuum, which allows nanoscale electrostatic gating of the material without exposing it to invasive nanoprocessing. An additional benefit is the vacuum between gates and material, which, unlike gate dielectrics, is free from charge traps. We demonstrate the operation and feasibility of the flip-chip setup by achieving quantum interference at integer quantum Hall states in a Fabry-Pérot interferometer based on a GaAs/AlGaAs 2DEG. Our results pave the way for the study of exotic phenomena including fragile fractional quantum Hall states by preserving the high quality of the material.
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Affiliation(s)
- Arjan J A Beukman
- QuTech and Kavli Institute of Nanoscience, Delft University of Technology , GA 2600 Delft, The Netherlands
| | - Fanming Qu
- QuTech and Kavli Institute of Nanoscience, Delft University of Technology , GA 2600 Delft, The Netherlands
| | - Ken W West
- Department of Electrical Engineering, Princeton University , Princeton, New Jersey 08544, United States
| | - Loren N Pfeiffer
- Department of Electrical Engineering, Princeton University , Princeton, New Jersey 08544, United States
| | - Leo P Kouwenhoven
- QuTech and Kavli Institute of Nanoscience, Delft University of Technology , GA 2600 Delft, The Netherlands
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Biesinger DEF, Scheller CP, Braunecker B, Zimmerman J, Gossard AC, Zumbühl DM. Intrinsic Metastabilities in the Charge Configuration of a Double Quantum Dot. PHYSICAL REVIEW LETTERS 2015; 115:106804. [PMID: 26382695 DOI: 10.1103/physrevlett.115.106804] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2015] [Indexed: 06/05/2023]
Abstract
We report a thermally activated metastability in a GaAs double quantum dot exhibiting real-time charge switching in diamond shaped regions of the charge stability diagram. Accidental charge traps and sensor backaction are excluded as the origin of the switching. We present an extension of the canonical double dot theory based on an intrinsic, thermal electron exchange process through the reservoirs, giving excellent agreement with the experiment. The electron spin is randomized by the exchange process, thus facilitating fast, gate-controlled spin initialization. At the same time, this process sets an intrinsic upper limit to the spin relaxation time.
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Affiliation(s)
- D E F Biesinger
- Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
| | - C P Scheller
- Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
- Swiss Federal Laboratories for Materials Science and Technology, EMPA, Überlandstrasse 129, CH-8600 Dübendorf, Switzerland
| | - B Braunecker
- Scottish Universities Physics Alliance, School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews KY16 9SS, United Kingdom
| | - J Zimmerman
- Materials Department, University of California, Santa Barbara, California 93106, USA
| | - A C Gossard
- Materials Department, University of California, Santa Barbara, California 93106, USA
| | - D M Zumbühl
- Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
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11
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Forster F, Petersen G, Manus S, Hänggi P, Schuh D, Wegscheider W, Kohler S, Ludwig S. Characterization of qubit dephasing by Landau-Zener-Stückelberg-Majorana interferometry. PHYSICAL REVIEW LETTERS 2014; 112:116803. [PMID: 24702402 DOI: 10.1103/physrevlett.112.116803] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2013] [Indexed: 06/03/2023]
Abstract
Controlling coherent interaction at avoided crossings and the dynamics there is at the heart of quantum information processing. A particularly intriguing dynamics is observed in the Landau-Zener regime, where periodic passages through the avoided crossing result in an interference pattern carrying information about qubit properties. In this Letter, we demonstrate a straightforward method, based on steady-state experiments, to obtain all relevant information about a qubit, including complex environmental influences. We use a two-electron charge qubit defined in a lateral double quantum dot as test system and demonstrate a long coherence time of T2 ≃ 200 ns, which is limited by electron-phonon interaction.
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Affiliation(s)
- F Forster
- Center for NanoScience & Fakultät für Physik, LMU-Munich, 80539 München, Germany
| | - G Petersen
- Center for NanoScience & Fakultät für Physik, LMU-Munich, 80539 München, Germany
| | - S Manus
- Center for NanoScience & Fakultät für Physik, LMU-Munich, 80539 München, Germany
| | - P Hänggi
- Institut für Physik, Universität Augsburg, 86135 Augsburg, Germany
| | - D Schuh
- Fakultät für Physik, Universität Regensburg, 93040 Regensburg, Germany
| | - W Wegscheider
- Fakultät für Physik, Universität Regensburg, 93040 Regensburg, Germany and Solid State Physics Laboratory, ETH Zurich, 8093 Zurich, Switzerland
| | - S Kohler
- Instituto de Ciencia de Materiales de Madrid, CSIC, 28049 Madrid, Spain
| | - S Ludwig
- Center for NanoScience & Fakultät für Physik, LMU-Munich, 80539 München, Germany
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12
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See AM, Pilgrim I, Scannell BC, Montgomery RD, Klochan O, Burke AM, Aagesen M, Lindelof PE, Farrer I, Ritchie DA, Taylor RP, Hamilton AR, Micolich AP. Impact of small-angle scattering on ballistic transport in quantum dots. PHYSICAL REVIEW LETTERS 2012; 108:196807. [PMID: 23003076 DOI: 10.1103/physrevlett.108.196807] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2011] [Revised: 03/08/2012] [Indexed: 06/01/2023]
Abstract
Disorder increasingly affects performance as electronic devices are reduced in size. The ionized dopants used to populate a device with electrons are particularly problematic, leading to unpredictable changes in the behavior of devices such as quantum dots each time they are cooled for use. We show that a quantum dot can be used as a highly sensitive probe of changes in disorder potential and that, by removing the ionized dopants and populating the dot electrostatically, its electronic properties become reproducible with high fidelity after thermal cycling to room temperature. Our work demonstrates that the disorder potential has a significant, perhaps even dominant, influence on the electron dynamics, with important implications for "ballistic" transport in quantum dots.
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Affiliation(s)
- A M See
- School of Physics, University of New South Wales, Sydney NSW 2052, Australia
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Petersson KD, Petta JR, Lu H, Gossard AC. Quantum coherence in a one-electron semiconductor charge qubit. PHYSICAL REVIEW LETTERS 2010; 105:246804. [PMID: 21231547 DOI: 10.1103/physrevlett.105.246804] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2010] [Revised: 11/02/2010] [Indexed: 05/27/2023]
Abstract
We study quantum coherence in a semiconductor charge qubit formed from a GaAs double quantum dot containing a single electron. Voltage pulses are applied to depletion gates to drive qubit rotations and noninvasive state readout is achieved using a quantum point contact charge detector. We measure a maximum coherence time of ∼7 ns at the charge degeneracy point, where the qubit level splitting is first-order insensitive to gate voltage fluctuations. We compare measurements of the coherence time as a function of detuning with numerical simulations and predictions from a 1/f noise model.
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Affiliation(s)
- K D Petersson
- Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
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Xu G, Torres CM, Song EB, Tang J, Bai J, Duan X, Zhang Y, Wang KL. Enhanced conductance fluctuation by quantum confinement effect in graphene nanoribbons. NANO LETTERS 2010; 10:4590-4594. [PMID: 20939609 DOI: 10.1021/nl1025979] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Conductance fluctuation is usually unavoidable in graphene nanoribbons (GNR) due to the presence of disorder along its edges. By measuring the low-frequency noise in GNR devices, we find that the conductance fluctuation is strongly correlated with the density-of-states of GNR. In single-layer GNR, the gate-dependence of noise shows peaks whose positions quantitatively match the subband positions in the band structures of GNR. This correlation provides a robust mechanism to electrically probe the band structure of GNR, especially when the subband structures are smeared out in conductance measurement.
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Affiliation(s)
- Guangyu Xu
- Department of Electrical Engineering, University of California at Los Angeles, Los Angeles, California 90095, United States.
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Shin YS, Obata T, Tokura Y, Pioro-Ladrière M, Brunner R, Kubo T, Yoshida K, Tarucha S. Single-spin readout in a double quantum dot including a micromagnet. PHYSICAL REVIEW LETTERS 2010; 104:046802. [PMID: 20366727 DOI: 10.1103/physrevlett.104.046802] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2009] [Indexed: 05/29/2023]
Abstract
We use photon-assisted tunneling (PAT) and an inhomogeneous Zeeman field to demonstrate spin-selective PAT readout with a double quantum dot. The inhomogeneous Zeeman field is generated by a proximal micromagnet, which provides different stray fields between the two dots, resulting in an energy difference between the interdot PAT of the up-spin state and that of the down-spin state. We apply various external magnetic fields to modify the relative filling weight between the up-spin and down-spin states and detect it by using a charge detection technique to probe the PAT induced charge delocalization in the double dot.
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Affiliation(s)
- Yun-Sok Shin
- Quantum Spin Information Project, ICORP, JST, Atsugi-shi, Kanagawa 243-0198, Japan.
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Simmons CB, Thalakulam M, Rosemeyer BM, Van Bael BJ, Sackmann EK, Savage DE, Lagally MG, Joynt R, Friesen M, Coppersmith SN, Eriksson MA. Charge sensing and controllable tunnel coupling in a Si/SiGe double quantum dot. NANO LETTERS 2009; 9:3234-3238. [PMID: 19645459 DOI: 10.1021/nl9014974] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
We report integrated charge sensing measurements on a Si/SiGe double quantum dot. The quantum dot is shown to be tunable from a single, large dot to a well-isolated double dot. Charge sensing measurements enable the extraction of the tunnel coupling t between the quantum dots as a function of the voltage on the top gates defining the device. Control of the voltage on a single such gate tunes the barrier separating the two dots. The measured tunnel coupling is an exponential function of the gate voltage. The ability to control t is an important step toward controlling spin qubits in silicon quantum dots.
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Affiliation(s)
- C B Simmons
- University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
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