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 A74: Spin Qubit Arrays IFocus
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Sponsoring Units: DQI Chair: Andre Saraiva, Diraq Room: Room 403/404 |
Monday, March 6, 2023 8:00AM - 8:36AM |
A74.00001: Adaptive real-time operations in small spin qubit arrays Invited Speaker: Ferdinand Kuemmeth Gate-controlled spin qubits offer tunability and programmable operation by voltage signals. Maturing devices from simple single- and two-qubit geometries to arrays of interconnected quantum dots poses challenges that arise for example from cross coupling and gate-offset drifts, necessitating efficient and autonomous operations in the high-dimensional control parameter space associated with qubit arrays. |
Monday, March 6, 2023 8:36AM - 8:48AM |
A74.00002: Quiver: quantum dot device control software Ian Jenkins For quantum dot qubit device technology to mature, we must develop improved methods for control, tune-up, and quantum characterization, verification, and validation (QCVV). A flexible software framework is required for both exploring methods to control growing arrays of devices and automating those methods to efficiently generate device statistics. Our newest generation of quantum control software, dubbed Quiver, meets these needs by providing flexible device control interfaces, automated tune-up routines, and reliable QCVV methods. In this talk we demonstrate the efficacy of Quiver by using it to automate a complex tune-up sequence on an array of 6 Si/SiGe quantum dots implemented with the SLEDGE architecture. |
Monday, March 6, 2023 8:48AM - 9:00AM |
A74.00003: An automated measurement sequence for the calibration of quantum dot arrays Reed Andrews Sequencing automated measurement routines in a way that is both efficient and optimal remains a notable challenge in the tune-up of real-world quantum dot devices that are subject to disorder. Here we describe a generally-applicable process for tuning both the charge occupancy and inter-dot coupling of an array of quantum dots, compensating for disorder and building towards coherent operation. We demonstrate the process on an array of 6 Si/SiGe quantum dots in the SLEDGE architecture [1]. We’ll show that using neural-network based analysis tools, physically-motivated voltage reconfigurations can be implemented to strategically traverse standard characterization techniques, with the explicit goal of conditioning a device’s physical state for qubit initialization, measurement, and control. |
Monday, March 6, 2023 9:00AM - 9:12AM |
A74.00004: Charge control in a 2x2 semiconductor quantum-dot array with shared control electrodes. Emmanuel Chanrion, Pierre-André Mortemousque, Baptiste Jadot, Martin Nurizzo, Arne Ludwig, Andreas D Wieck, Christopher Bäuerle, Matias Urdampilleta, Tristan Meunier Quantum computing offers a way to solve physics and computing problems that cannot be solved in reasonable times by classical computers. However, quantum computers are prone to errors, which require encoding the information of a single logical quantum-bit (qubit) into many physical qubits. Consequently, a universal quantum computer outperforming current supercomputers involves controlling millions of qubits. In this context, spin qubit in quantum-dot (QD) arrays are a good candidate thanks to their compatibility with standard semiconductor manufacturing. |
Monday, March 6, 2023 9:12AM - 9:24AM |
A74.00005: Reliable Fabrication of Multi-Spin Qubit Devices in 28Si/SiGe Heterostructures Sergey V Amitonov, Larysa Tryputen, Amir Sammak, Saurabh Karwal, Önder Gül, Yoram Vos, Tumi Makinwa, Rick N Wasserman, Delphine B Brousse, David J Michalak, Nodar Samkharadze, Giordano Scappucci, Lieven M Vandersypen, Rabah Hanfoug Well-controlled and reliably operated multi-quantum-dot devices are key component of future spin-based quantum computers. We report state-of-the-art fabrication methods of multi-quantum dot linear arrays that are defined in isotopically purified in-house grown 28Si/SiGe heterostructures for spin qubit applications. |
Monday, March 6, 2023 9:24AM - 9:36AM |
A74.00006: Large-scale characterization workflow of industrial grade Si-based qubit devices Pierre A Mortemousque On-going efforts in scaling-up solid-state spin qubits are hindered by the need for a characterization workflow that assesses the correct device operation at low temperature, and for the associated quality and variability metrics. We present here our fast characterization methodology for qubit devices, and present wafer-level (WL) measurements on qubit-array structures at both 300K and 1K. Transistor-like metrics and material characterization provide feedbacks to process integration. They must be enriched by WL measurements at 1K that contain specific information about the electron confinement in a quantum dot. As such, they are crucial for process evaluation as well as device screening before continuing to mK characterization. We measure and automatically extract for the first time WL quantum dot metrics. |
Monday, March 6, 2023 9:36AM - 9:48AM |
A74.00007: An elongated quantum dot as a distributed charge sensor Sofia M Patomäki, James Williams, Fabrizio Berritta, Constance Lainé, Michael A Fogarty, Ross Leon, Anasua Chatterjee, Julien Jussot, Stefan Kubicek, Bogdan Govoreanu, Ferdinand Kuemmeth, John Morton, Fernando Gonzalez-Zalba Elongated quantum dots have been explored as a way to mediate a spin-spin interaction between spatially separated semiconductor quantum dots. Increasing the separation between quantum dots has potential advantages for the scalability of dense two-dimensional arrays, in gate routing and the integration of sensors and reservoirs. Here, we study a metal-oxide-silicon (MOS) device where two quantum dot arrays are separated by an elongated quantum dot (340 nm long, 50 nm wide). We monitor charge transitions of the elongated quantum dot by measuring radiofrequency single-electron currents to a reservoir to which we connect a lumped-element resonator. This elongated `single electron box' is used to achieve charge sensing of remote quantum dots in each array, separated by a distance of over 0.5 μm. Simultaneous charge detection on both ends of the elongated dot demonstrates that the charge is well distributed across its nominal length, supported by the simulated quantum-mechanical electron density. Our results illustrate how single-electron boxes can be realised with versatile footprints to enable compact qubit processors, offering remote sensing as well as the possibility of mediated coupling. |
Monday, March 6, 2023 9:48AM - 10:00AM |
A74.00008: Quantum dot arrays in linear and two-dimension geometries in silicon Saurabh Karwal, Sergey V Amitonov, Larysa Tryputen, Amir Sammak, David J Michalak, Marcel Meyer, Florian K Unseld, Corentin Déprez, Timo v Abswoude, Lieven M Vandersypen, Giordano Scappucci, Menno Veldhorst The performance of quantum computers can be traced back to the quality of quantum devices. Quantum states are fragile and may lose their state due to decoherence caused by a noisy environment [1,2,3]. The growth of low defect, and low disorder materials and reliable device fabrication is required. In this work, we report on state-of-the-art fabrication methods of spin qubit devices that are defined in isotopically purified in-house grown 28Si/SiGe heterostructures. We report developments in the fabrication process of two-dimensional quantum dot arrays in 28Si/SiGe heterostructures as a promising way forward for scaling up [4]. Such a device architecture also allows for tunnel coupling between two adjacent quantum dots in two-dimensions. Furthermore, scalable quantum processor might also require the use of shared plunger and barrier gates as has been demonstrated in the Ge/SiGe material platform [5], which entails very high level of device uniformity in terms of control voltages required per qubit. Here, we also report on fabrication process of linear quantum dot array devices that were used to demonstrate the electrical tuning of plunger gates to achieve higher degree of electrical uniformity, thereby significantly reducing variations in the turn-on voltages [6]. |
Monday, March 6, 2023 10:00AM - 10:12AM |
A74.00009: Modelling the electronic structure of many electrons (> 100) with self-consistent Hartree-Fock Simulations MengKe Feng, Dylan Liang, Zeheng Wang, Jesus D Cifuentes Pardo, Philip Mai, Andrew S Dzurak, Arne Laucht, Andre Saraiva In moving towards building a scalable quantum computer, it becomes important to consider the role of long-range interconnects between local arrays in scalable architectures. In particular, we are interested in building a multi-electron mediator as an interconnect on silicon MOS heterostructures. Due to the unique properties of silicon, the physics of such a mediator has to be understood for us to fully utilize it to its best. We demonstrate here that we are able to simulate multi-electron systems of up to hundreds of electrons using the Hartree-Fock method. We show the non-trivial formation of multi-electron wavefunctions and also the formation of systems with well-defined spin, paving the way for multi-electron mediators in silicon MOS systems. |
Monday, March 6, 2023 10:12AM - 10:24AM |
A74.00010: A new approach to simulating electron densities obtained in scanning gate microscopy of Si/SiGe quantum dot devices Gordian Fuchs, Artem O Denisov, Christopher R Anderson, Mark F Gyure, Jason R Petta To advance the understanding of what limits the valley degree of freedom in silicon-based spin qubits, a cryogen-free scanning gate microscope (SGM) has been demonstrated [1]. Along with probing the microscope’s potential to enable spatial mapping of the valley splitting in Si/SiGe quantum dot (QD) devices, semiconductor quantum device simulations were implemented [2]. However, these simulations assume a 2D device gate geometry and omit the role of the tip bias and the 3D overlapping gate architecture [3] in the charge occupation of the QD device. Here, we present recent efforts on using domain decomposition methods to combine an electrostatics model of the tip bias and the 3D overlapping gate structure with an approximate solution to the 3D Schroedinger-Poisson equation [4]. These efforts allow us to explore the effect of the tip bias of the microscope on the electron density of a Si/SiGe quantum dot and compare with experimental data. |
Monday, March 6, 2023 10:24AM - 10:36AM |
A74.00011: Spin Filling in a Silicon Quantum Dot Array Fan Fei, Xiqiao Wang, Ehsan Khatami, Jonathan Wyrick, Pradeep N Namboodiri, Joseph B Fox, Albert F Rigosi, Richard M Silver NIST is using atomically precise fabrication to develop devices for use in quantum information processing. We are using hydrogen-based scanning probe lithography for deterministic placement of individual dopant atoms with atomically aligned gates to fabricate arrayed few-donor devices for analog quantum simulation research. Understanding electron configurations and transport in small arrays is critical to simulating larger systems and exploring the huge parameter space of the Fermi-Hubbard model. |
Monday, March 6, 2023 10:36AM - 10:48AM |
A74.00012: AFM-based Charge-Locking in Silicon Quantum Devices Artem O Denisov, Gordian Fuchs, Pengcheng Chen, seongwoo oh, Jason R Petta We use the tip of an atomic force microscope (AFM) to charge floating metallic gates in multilayer Si/SiGe quantum dot (QD) devices. Acting as a perfect and movable cryogenic switch, the tip provides reproducible and non-destructive charge-locking with single-electron precision on the floating gate. Biasing a gate with an AFM tip allows us to reduce the footprint of a single plunger gate down to an isolated ~100 nm island. By sensing the real-time retention of the locked charge, we show that the discharging of the floating gate proceeds in discreet steps. By measuring the distribution of the single-electron leakage events, we extract the resistance of the tunnel junction between overlapping gate layers R~10^{19} Ohm – a value immeasurable by conventional means. We found the average discharge rate to be of the order of 1 electron per few seconds in overlapping gate architecture and multiple hours for single-layer devices. The random-access nature of the AFM-tip charging approach allows us to reduce the footprint of a single plunger gate down to a fundamental limit with the potential to tune a 2D array of arbitrary size. |
Monday, March 6, 2023 10:48AM - 11:00AM |
A74.00013: Frequency Tunable and Q Switchable Superconducting Resonators for Spin Qubit Control Noah D Johnson, Anthony Sigillito, Mridul Pushp Most Si/SiGe quantum processors depend on coupling to on-chip micromagnets for quantum control via electrically driven spin resonance (EDSR). While electrical control via micromagnets has been shown to yield high fidelity qubit operations [1], they induce a synthetic spin-orbit interaction, which reduces dephasing and relaxation times [2,3], and provides significant scaling challenges. Here, by utilizing high kinetic inductance superconductors, we demonstrate a versatile resonator design that offers the frequency and Q tunability necessary for developing fast, magnetically driven resonant gates in our micromagnet-free architecture. Initial design considerations and device performance will be discussed. |
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