Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session Y74: Semiconducting Qubits VFocus
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Sponsoring Units: DQI Chair: Stefano Bosco, University of Basel Room: Room 403/404 |
Friday, March 10, 2023 8:00AM - 8:36AM |
Y74.00001: Optimizing coherence of germanium spin qubits. Invited Speaker: Nico Hendrickx The prospect of building quantum circuits using advanced semiconductor manufacturing techniques position quantum dots as an attractive platform for quantum information processing. Initial demonstrations of one and two-qubit logic have been performed in gallium arsenide and later silicon. However, until recently, interconnecting larger spin qubit systems has remained a challenge. |
Friday, March 10, 2023 8:36AM - 8:48AM |
Y74.00002: A singlet-triplet hole-spin qubit in planar silicon Scott D Liles, Aaquib Shamim, Ik Kyeong Jin, Joseph W Hillier, Matthew Rendell, Isaac Vorreiter, Wee Han Lim, Fay E Hudson, Andrew S Dzurak, Alex R Hamilton Spin Qubits in group IV materials are promising candidates for implementing quantum processors compatible with modern CMOS technology. Recently, hole spins have been demonstrated to be highly suitable for spin qubits, since the strong spin-orbit interaction for holes enables rapid all-electric spin control and offers a wide range of control over key parameters such as the g-tensor and spin coherence time [1]. However, to date there have been very few experimental demonstrations of hole-spin qubits, hence fundamental questions about the operation and optimisation of hole-spin qubits remain open. |
Friday, March 10, 2023 8:48AM - 9:00AM |
Y74.00003: Modeling few-hole quantum dots in Ge/SiGe: g-factors and qubit properties Mitchell I Brickson, Noah T Jacobson, Leon Maurer, Tzu-Ming Lu, Dwight R Luhman, Andrew D Baczewski We present a detailed numerical model for single- and few-hole quantum dots in Ge/SiGe qubit devices. The impact of the finite confinement, split-off band, inter-hole interactions, and image charges on the energy level structure, g-tensors, electric dipole spin resonance (EDSR) Rabi frequencies, and dephasing rates are assessed. Our model is compared to recent magnetospectroscopy experiments on a few-hole device in which a simpler model was able to reproduce results for the first shell, but not the higher ones. We find that accounting for these additional effects better rationalize prior experimental observations and elaborate on their relative importance. We also consider the potential utility of higher filling Ge hole quantum dots for qubit applications. |
Friday, March 10, 2023 9:00AM - 9:12AM |
Y74.00004: Towards 2-Qubit Operations of Hole Spins in Ge/Si Nanowires above 1K Miguel J Carballido, Simon Svab, Rafael S Eggli, Pierre Chevalier Kwon, Simon Geyer, Rahel Kaiser, Leon C Camenzind, Florian N Froning, Erik P. A. M. Bakkers, Taras Patlatiuk, Stefano Bosco, J. Carlos Egues, Daniel Loss, Dominik M Zumbuhl We report on two highly electrically-tunable hole-spin-qubits in a Ge/Si core-shell nanowire device operated at 1.5 K |
Friday, March 10, 2023 9:12AM - 9:24AM |
Y74.00005: Effects of the spin-orbit coupling on hole spin qubits Omadillo Abdurazakov, Charles Tahan, Yun-Pil Shim Recent experimental and theoretical progress in hole spin qubits in germanium quantum dots made it a promising platform for scalable semiconductor qubit devices. One of the main advantages of the hole qubits over the electron qubits is the strong spin-orbit (SO) coupling, which allows the implementation of electric dipole spin resonance (EDSR) without microstructures to create local magnetic fields for single-qubit gate operations. But the presence of the SO coupling also makes the hole qubits vulnerable to charge noises. We present a theoretical analysis of the effects of the Rashba-type SO coupling on the hole spin qubits in a realistic quantum dot confinement with anisotropy and anharmonicity. Conditions for EDSR operations and for conserving the spin qubit coherence will be presented. |
Friday, March 10, 2023 9:24AM - 9:36AM |
Y74.00006: Spin-orbit enhancement and g-factor renormalization in Si/SiGe heterostructures with oscillating Ge concentration Benjamin D Woods, Mark Friesen, Robert J Joynt, Mark A Eriksson We show that Ge concentration oscillations within the quantum well region of a Si/SiGe heterostructure can significantly enhance the spin-orbit coupling of the low-energy conduction-band valleys. Specifically, we find that for Ge oscillation wavelengths near λ = 1.57 nm a Dresselhaus spin-orbit coupling is produced that is over an order of magnitude larger than what is found in conventional Si/SiGe heterostructures without Ge concentration oscillations. Furthermore, enhanced inter-subband spin-orbit coupling leads to significant g-factor renormalization, creating a difference of ~ 0.01-0.04 between the g-factors of the ground and excited valleys for appropriate Ge oscillation wavelength and magnetic field direction. We provide an explanation for these enhancements, which involves the Ge concentration oscillations producing wavefunction satellite peaks a distance 2π/λ away in momentum space from each valley, which then couple to the opposite valley through Dresselhaus spin-orbit coupling. We also explore how the spin-orbit enhancement and g-factor renormalization can be exploited for qubit manipulation. For example, our results indicate that the enhanced spin-orbit coupling can enable fast spin manipulation within Si quantum dots using electric dipole spin resonance in the absence of micromagnets with Rabi frequencies of 100s of MHz. |
Friday, March 10, 2023 9:36AM - 9:48AM |
Y74.00007: Fine-tuning the quantum well thickness in 28Si/SiGe heterostructures Davide Degli Esposti, Lucas Stehouwer, Davide Costa, Cornelius Carlsson, Larysa Tryputen, Sergey V Amitonov, Amir Sammak, Giordano Scappucci Advancing the materials science of quantum devices plays an essential role in pursuing larger spin-based quantum processors with more functionality. Recently, we systematically engineered the material stack focusing on the semiconductor-dielectric interface [1] and the thickness of the buried 28Si quantum well [2]. |
Friday, March 10, 2023 9:48AM - 10:00AM |
Y74.00008: Si/SiO2 Roughness: Variability, tunability and crosstalk in CMOS spin qubits Jesus D Cifuentes Pardo, Tuomo I Tanttu, Jonathan Y Huang, Will Gilbert, Ensar Vahapoglu, Santiago Serrano, MengKe Feng, Arne Laucht, Chih-Hwan Yang, Christopher Escott, Rajib Rahman, Fay E Hudson, Wee Han Lim, Andre Saraiva, Andrew S Dzurak Fault tolerant quantum computation will require building processors with millions of qubits. The CMOS spin qubit technology - fabricated with the same materials and techniques as transistors - promises a highly scalable pathway to achieve these numbers. Initial experiments in two-qubit devices have demonstrated high gate fidelities and long coherence times. However, CMOS qubits are defined by the spin state of single electrons accumulated at the Si/SiO2 interface, making them susceptible to potential sources of disorder in the oxide. Even though modern fabrication processes lead to reliable and stable oxides, their growth leads to an atomically rough interface. In this talk, we will explore the impact of this roughness on the most important qubit parameters. By comparing atomistic simulations in random realistic surfaces with measurements of up to 10 qubits in 5 identical devices, we obtained a reliable estimate of the variability of our qubits. Each of these qubit parameters has some range of electrical tunability from nearby gates that enables local controllability. We show that the sign and the magnitude of the Stark shift from each gate depends on the local surface profile too. This is a source of crosstalk as gate detunings can cause lateral displacements in the quantum dots nearby. We will analyze the possible effects of this crosstalk in a scalable qubit architecture. Based on these statistics, realistic protocols for scaling CMOS spin qubits may be developed. |
Friday, March 10, 2023 10:00AM - 10:12AM |
Y74.00009: Progress in development of the silicon spin qubit based back-end for QuTech’s Quantum Inspire platform Tumi Makinwa, Nodar Samkharadze, Harold B Meerwaldt, Pieter T Eendebak, Yoram Vos, Önder Gül, Larysa Tryputen, Saurabh Karwal, Sergey V Amitonov, James G Kroll, Amir Sammak, Richard Versluis, Jasper Winters, Lieven M Vandersypen, Peter Verhoeff Over the last 4 years, Quantum Inspire (QI) has provided a quantum computing platform that enables users to access quantum technology for the aims of education and algorithm development (www.quantum-inspire.com). Using the platform can be done through either the web editor using QASM, or through any other editor using the Quantum Inspire SDK. Since its launch in 2018, Quantum Inspire has been expanding in scope through, for example, the implementation of additional quantum technologies (Starmon-5) and more powerful hardware for its simulator backend. |
Friday, March 10, 2023 10:12AM - 10:24AM |
Y74.00010: Fast singlet-triplet qubit driven by magnetic field gradient in isotopically purified silicon Younguk Song, Jonginn Yun, Jehyun Kim, hyeongyu jang, Jaemin Park, Wonjin Jang, Hanseo Sohn, Satoru Miyamoto, Kohei M Itoh, Dohun Kim The Micromagnet technique has proven effective for manipulating spins in semiconductor quantum dot (QD) nanostructures, especially in silicon. Although the placement of on-chip micromagnets has enabled single-spin qubits in silicon with gate fidelity to reach surface code-based error correction threshold, corresponding results using encoded spin qubits, for example, single-triplet qubits with high-quality quantum oscillations, have not been demonstrated. Instead, the spin-valley coupling has been recently used to enhance the electrical controllability of two-electron spin qubits in silicon at the expense of increased susceptibility to charge noise. Here, we demonstrate fast singlet-triplet qubit oscillation (>100MHz) in isotopically purified 28-Si/SiGe substrate with an on-chip micromagnet in the regime where valley-splitting in each quantum dot exceeds 300 ueV. Combining rf-reflectometry-based single-shot readout and adaptive initialization, we show that the oscillation quality factor of an encoded spin qubit over 300 can be achieved. We further present the measurement of single-triplet qubit oscillation and variation of coherence time near the micro-magnet's magnetization reversal, offering a route to in-situ tune magnetic field gradient and hence the Larmor frequency of the singlet-triplet qubit in silicon. |
Friday, March 10, 2023 10:24AM - 10:36AM |
Y74.00011: Flip-Chip Gating of Heterostructure Quantum Materials Jay C LeFebvre, Tzu-Ming Lu, Matthew Jordan, Michael P Lilly, John Nogan, Dwight R Luhman, Martin Rudolph Semiconductor qubits are achieving circuits of greater complexity, but due to overhead requirements in fabrication, few groups have the capability to develop this technology. One approach to increase the rate of development of semiconductor-based quantum computing is to ease the barrier to entry for researchers through a simplified, yet generalized, device architecture. This, in turn, will provide faster materials characterization, currently a significant limiter in semiconductor qubits. We propose to develop a flip-chip device platform containing all control and readout elements for characterization of lateral quantum dots in materials of interest without discrimination. The gap between the chips is engineered via precise etching of mesas and hard stop posts and is attached via indium bump bonds. The proposed architecture of flip-chip-based qubit control and readout has applications in advancing to higher density quantum circuits and reducing surface preparation complexity. Progress towards achieving a flip-chip gated quantum dot with charge sensing via dispersive gate readout will be presented. We demonstrate the flip-chip gating of a Hall bar structure to qualify the fabrication process by directly comparing to a conventional fabrication-on-die process and estimate gate coupling to the quantum well. |
Friday, March 10, 2023 10:36AM - 10:48AM |
Y74.00012: High bandwith high sensitivity electronic thermometry in SiMOS transistors Victor Champain, Victor Champain, Vivien Schmitt, Benoit Bertrand, Heimanu Niebojewski, Louis Hutin, Maud Vinet, Xavier Jehl, Clemens Winkelmann, Silvano De Franceschi, Boris Brun-Barriere In the worldwide efforts to build the first useful quantum processor, semiconductor quantum dots are attracting increasing interest owing to their scalability prospects. In this approach, the qubits can be encoded in the spin degree of freedom of individual electronic charges localized in gate-defined potential wells. Recent work indicates that the heat generated by the manipulation and read-out of qubits constitutes a bottleneck for the efficient operation of large-scale quantum processors. |
Friday, March 10, 2023 10:48AM - 11:00AM |
Y74.00013: Andreev bound state dynamics in phase- and gate-tunable InAs Nanowire Josephson weak links Manas Ranjan Sahu, Cyril Metzger, Francisco Matute-Cañadas, Peter Krogstrup, Jesper Nygard, Alfredo L Yeyati, Marcelo F Goffman, Cristian Urbina, Hugues Pothier Localized fermionic modes called Andreev bound states (ABSs) in InAs nanowire - superconductor weak links have been utilized in the past to realize Andreev pair and spin qubits [1, 2]. The occupation of ABSs is not only controlled by microwave drive tones, it also varies due to pair recombination, quasiparticle poisoning, relaxation and excitation. In general, several configurations of the ABS occupations are involved. From the measurement of how Andreev qubits relax to the steady state after an excitation pulse, we extract the transition rates between configurations and analyse their dependence on the phase across the weak link and on the gate voltage controlling the electronic properties of the nanowire weak link. |
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