Bulletin of the American Physical Society
APS March Meeting 2023
Las Vegas, Nevada (March 510)
Virtual (March 2022); Time Zone: Pacific Time
Session W74: Semiconducting Qubits IVFocus

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Sponsoring Units: DQI Chair: Andrey Kiselev, HRL Laboratories, LLC Room: Room 403/404 
Thursday, March 9, 2023 3:00PM  3:36PM 
W74.00001: Building small, fast and hot hole spin qubits in Si and Ge Invited Speaker: Dominik M Zumbuhl Quantum computers hold the potential to solve tasks exponentially faster than classical computers. 
Thursday, March 9, 2023 3:36PM  3:48PM 
W74.00002: Modelling of planar germanium hole qubits in electric and magnetic fields Maximilian Russ, ChienAn Wang, Giordano Scappucci, Menno Veldhorst Holebased spin qubits in strained planar germanium quantum wells have received considerable attention due to their favourable properties and remarkable experimental progress. The sizeable spinorbit interaction in this structure allows for efficient electric qubit operations while also coupling the qubit to electrical noise. 
Thursday, March 9, 2023 3:48PM  4:00PM 
W74.00003: Hole spin qubits in semiconductor quantum dots Jiawei Wang, Xuedong Hu, Herbert F Fotso Hole spin qubits in semiconductor quantum dots allow ultrafast electrical control, and are considered an intriguing candidate as the building block for a scalable quantum computer. Here we develop a theory with the objective of understanding how an alternating electric field can couple the two heavy hole states in a twodimensional quantum dot to allow electric dipole 
Thursday, March 9, 2023 4:00PM  4:12PM 
W74.00004: Hole spin manipulation in inhomogeneous and nonseparable electric fields Esteban Rodriguez, Biel Martinez Diaz, YannMichel Niquet, Jose Carlos AbadilloUriel The usual models for electrical spin manipulation in semiconductor quantum dots assume a separable confinement potential in the spatial dimensions and/or a homogeneous AC driving field. However, the electric field induced by the gates in quantum dot devices is not fully separable and displays inhomogeneities. We address the electrical manipulation of hole spins in semiconductor heterostructures subject to inhomogeneous vertical electric fields and/or inplane AC electric fields. We consider Ge quantum dots electrically confined in a Ge/GeSi quantum well as an illustration. We show that the coupling between the vertical and inplane motions of the hole gives rise to an additional spinorbit coupling mechanism (beyond the usual linear/cubic in momentum Rashba terms) that modulates the principal axes of the hole gyromagnetic gmatrix. This nonseparability mechanism can be of the same order of magnitude as Rashbatype interactions enabling spin manipulation when the magnetic field is applied in the plane of the heterostructure even when the dot is symmetric. More generally, we show that Rabi oscillations in strongly patterned electric fields harness a variety of gfactor modulations. We discuss the implications for the design, modeling and understanding of hole spin qubit devices.

Thursday, March 9, 2023 4:12PM  4:24PM 
W74.00005: Towards Si finFET quantum devices with reproducible behavior Matthias Mergenthaler, Felix Schupp, Noelia VicoTrivino, Konstantinos Tsoukalas, Lisa Sommer, Eoin G Kelly, Michele Aldeghi, Nico Hendrickx, Leonardo Massai, Andreas V Kuhlmann, Ute Drechsler, Antonis Olziersky, Peter Müller, Stephan Paredes, Gian Salis, Patrick HarveyCollard, Andreas J Fuhrer Hole spin qubits in Si finFETs show great promise for a quantum computing platform exhibiting fast and all electrical qubit control, even when operated at temperatures above 1K. While charge noise affects all platforms, disorder is one of the main limitations in current SiMOS qubit technology. 
Thursday, March 9, 2023 4:24PM  4:36PM 
W74.00006: Quantum mechanical modeling of electron spins in realistic gate defined double quantum dots. M.Mohamed El Kordy Shehata, George Simion, Fahd A. Mohiyaddin, Ruoyu Li, Asser Elsayed, Clement Godfrin, Danny Wan, Massimo Mongillo, Kristiaan De Greve, Pol Van Dorpe Spin qubits in semiconductors are front candidates for quantum computation, given their long coherence times [1]. Benefiting from decades of development in CMOS technologies [2], electrons in gatedefined quantum dots promise a platform for large scale integration of spin qubits. With recent demonstrations of high fidelity twoqubit gates[3,4], comes the need for active control over the exchange interaction that drives them. As such, a more comprehensive understanding of the exchange interaction in realistic devices and its dependence on control and environmental parameters is critical for spinbased quantum computation. The conditions for qubits' operation, on a small or large scale, are dictated by the underlying device architecture, choice of material, externally applied voltages and charge noise environment which has been shown to be a limiting factor for spin qubits. In this work, we propose a modelling framework that bridges a devices physical and operational conditions to the qubit energy space. The model combines electrostatic simulations and full configuration interaction (FCI) methods to estimate exchange interaction. Furthermore, the inclusion of any external potentials allows to study the effect of charge noise. This model opens a window for a deeper insight into spin qubit operation in semiconductors by estimating a critical metric represented in exchange coupling, its dependence on a device’s physical parameters and its sensitivity to the performancelimiting charge noise. 
Thursday, March 9, 2023 4:36PM  4:48PM 
W74.00007: Characterization of ultralow charge noise Silicon MOS quantum dots fabricated in a full 300mm CMOS platform Asser Elsayed, Mohamed Shehata, Clement Godfrin, Ruoyu Li, Stefan Kubicek, Shana Massar, Yann Canvel, Arame Thiam, Julien Jussot, Massimo Mongillo, Danny Wan, Pol Van Dorpe, Kristiaan De Greve Silicon spin qubits are among the most promising candidates for large scale quantum computers, due to their excellent coherence and compatibility with CMOS technology for upscaling [14]. Advanced industrial CMOS processes are engineered to allow waferscale uniformity and high device yield. However, these processes cannot be directly carried over to spin qubits due to different designs and operating conditions. 
Thursday, March 9, 2023 4:48PM  5:00PM Author not Attending 
W74.00008: Interacting TwoLevel Systems as a Source of 1/f Noise in Semiconductor Quantum Dot Qubits Dan Mickelsen, Herve M Carruzzo, Clare C Yu Charge noise in quantum dots has been observed to have a 1/f spectrum. We propose a model in which a pair of quantum dots are coupled to a 2D bath of fluctuators that have electric dipole moments and that interact with each other, i.e., with the other fluctuators. We simulate the bath of electric dipole fluctuators with a 2D Ising spin glass in the presence of a ground plane representing metal gates above the oxide layer containing the fluctuators. We calculate the resulting fluctuations in the electric potential at the two quantum dots that lie below the oxide layer. We report on the electric potential noise spectra at the quantum dots and the cross correlation in the noise between the two quantum dots. 
Thursday, March 9, 2023 5:00PM  5:12PM 
W74.00009: Energy dissipation in macroscopic quantum tunnel junctions Edgar J Patino, Leonardo Rios E, Neelima Kelkar We study energy dissipation, in large quantum tunnel junctions, by applying voltages just below barrier height up to break down voltages. Moreover, by lowering the temperature and adjusting the applied voltage to the junction, the effect on dissipation caused by the variation in barrier height relative to the energy of the incident particle is empirically examined. Here, we propose a model that considers the energy dissipated during quantum tunneling processes in solid state junctions. 
Thursday, March 9, 2023 5:12PM  5:24PM 
W74.00010: Effects of leakage on the realization of a discrete time crystal in a chain of singlettriplet qubits Robert E Throckmorton We consider the effects of leakage on the ability to realize a discrete time crystal (DTC) in a semiconductor quantum dot linear array being operated as a chain of singlettriplet (ST) qubits. This system realizes an Ising model with an effective applied magnetic field, plus additional terms that can cause leakage out of the computational subspace. We demonstrate that, in the absence of these leakage terms, this model theoretically realizes a DTC phase over a broad parameter regime for six and eight qubits, with a broader parameter range for the eightqubit case. We then reintroduce the leakage terms and find that the DTC phase disappears entirely over the same parameter range if the system is only subject to a uniform magnetic field, which does not suppress leakage. However, we find that the DTC phase can be restored if the system is instead subject to a magnetic field that alternates from qubit to qubit, which suppresses leakage. We thus show that leakage is a serious problem for the realization of a DTC phase in a chain of ST qubits, but is by no means insurmountable. Our work suggests that experiments manifesting smallsystem stable DTC should be feasible with currently existing quantum dot spin qubits. 
Thursday, March 9, 2023 5:24PM  5:36PM 
W74.00011: A realizable time crystal of four silicon quantum dot qubits Nathan L Foulk We demonstrate that exciting possible realizations of quantum Floquet matter are within reach for modern silicon spin qubits based in quantum dots, most notably the discrete time crystal (DTC). 
Thursday, March 9, 2023 5:36PM  5:48PM 
W74.00012: Optimizing charge dynamics in quantum dot systems Brian C Leininger, Mario F Borunda The current mission to design, develop and implement solidstate quantum computing processes invokes the need to control the charge dynamics within a device coherently. Devices built on quantum dot technology can be simulated as combinations of single/manyparticle quantum wells that could be implemented as computational qubits. Here we solve, via exact diagonalization, the states of a singleelectron quantum dot system, utilizing the OCTOPUS software package. Following, we implement from the same software, quantum optimal control theory (QOCT), to determine an optimal laser field that transitions a single charge from an initial state to the desired target state, (i) minimizing the time of transition and (ii) maximizing the overlap between the obtained final state and chosen target state. Both goals can be met while remaining within the range of experimentally accessible frequencies, aiding in bridging the gap between theory and experiment. Consequently, these results can provide insight into the development, initialization, and control of quantum dot systems for use in the design of solidstate quantum information devices. 
Thursday, March 9, 2023 5:48PM  6:00PM 
W74.00013: Entanglement dynamics of an Ising spin chain coupled to a central ancilla Linta Joseph, Joseph C Szabo, Nandini Trivedi, Chandrasekhar Ramanathan Characterizing the spread of entanglement in manybody quantum systems is of both fundamental and applied interest. Coupling a controllable ancilla to a manybody system could allow us to quantify the entanglement dynamics of a system. Two important questions that arise are: 1) what information can we gain about the system by measuring the ancilla? and 2) does the ancilla influence the entanglement dynamics of the system? Szabo and Trivedi have characterized the entanglement dynamics of the transverse field Ising chain with the spins coupled uniformly to a central bosonic ancilla using different entanglement metrics including a novel one called multipartite entanglement loss (MEL) [1]. In this work, we augment this investigation using the eigenstate entanglement spectrum (EES) and the entanglement spectrum statistics (ESS) and compare the insights to those from the MEL. EES characterizes the bipartite entanglement of eigenstates of the manybody Hamiltonian. ESS characterizes the growth of bipartite entanglement during time evolution of an initial product state under the Hamiltonian. We use exact diagonalization to explore the transition of the statistics from a Gaussian Orthogonal Ensemble (GOE) to a Poisson distribution as the transverse field strength and the coupling strength to the ancilla are varied. Finally, we replace the central bosonic ancilla with a spin qubit and explore the consequences of nonuniform spinancilla couplings. 
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