Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session F39: Semiconductor Qubits IIIFocus Recordings Available
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Sponsoring Units: DQI DCMP Chair: Vanita Srinivasa, URI Room: McCormick Place W-196A |
Tuesday, March 15, 2022 8:00AM - 8:36AM Withdrawn |
F39.00001: Coupling semiconductor electron and hole spin qubits to superconducting resonators Invited Speaker: Monica Benito The latest experimental progress in fabrication of one- and two-dimensional sizable arrays of QDs suggest that quantum information science applications are feasible in these devices, as originally envisioned by Loss and DiVincenzo. Spin qubits in Si and Ge are considered strong candidates for realizing a large-scale quantum processor due to the small qubit dimensions, compatibility with CMOS technology, long coherence times and possibility to operate beyond 1 Kelvin. Important challenges concerning scalability of spin qubits defined on QDs can be overcome by turning the qubits electrically addressable. In the case of electrons one can take advantage of the intrinsic spin-orbit (SO) coupling or gradients of magnetic field (for example created by external micromagnets). The physics of holes, dictated by the Luttinger-Kohn Hamiltonian, has attracted much attention lately because it naturally brings the electrical handle thanks to a strong SO coupling without analogous in electron systems. |
Tuesday, March 15, 2022 8:36AM - 8:48AM |
F39.00002: Spin decoherence due to Ampere field fluctuation from acoustic phonons Xiaoliang Zhang, Yu Yue, Jia Chen, Sam Dillon, Yiyuan Chen, Haiping Cheng, Xiaoguang Zhang We compute the decoherence time of electron spin under the magnetic field produced by the phonon motion of the ions. By using the linear dispersion relation in elastic mediums, the magnetic field due to acoustic phonon motion and the time correlation function of the magnetic field are calculated numerically. We then solve the Redfield equation of motion for the reduced density matrix, which yields the decoherence time of electron spin from the time correlation function of the magnetic field. The calculations are carried out for both in NV center and in semiconductor quantum dots. The NV center result of SiC shows the onsite field dominates the decoherence time. The quantum dot calculation of GaAs, InSb, and InAs shows all atoms in dot contribute. |
Tuesday, March 15, 2022 8:48AM - 9:00AM |
F39.00003: Anisoptropy and Mixing of Surface Acoustic Waves Zongye Wang
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Tuesday, March 15, 2022 9:00AM - 9:12AM |
F39.00004: Towards High-Impedance Surface Acoustic Wave Resonators for Quantum Information Processing Tze Yu Li, Yadav P Kandel, John Nichol Inspired by quantum circuit electrodynamics systems, quantum acoustic devices, like surface acoustic wave (SAW) resonators have emerged as powerful tools for quantum information processing in the gigahertz frequency range. Specifically, piezoelectric SAW resonators could be used to couple distant spin qubits in semiconductor quantum dots. Potential benefits of SAW resonators as quantum interconnects include the ability to operate in high magnetic fields and at elevated temperatures. However, strong spin-phonon coupling requires a large characteristic impedance associated with the SAW resonator. We discuss our efforts toward realizing SAW resonators with characteristic impedances exceeding 50Ω. To reach such levels of impedance, we use Gaussian SAW resonators on LiNbO3 to generate tightly confined phonon modes with strong piezoelectric coupling. Apart from the possibility of coupling distant spin qubits, these high-impedance SAW resonators may also be useful for interfacing microwave and optical photons for quantum information processing. |
Tuesday, March 15, 2022 9:12AM - 9:24AM |
F39.00005: Configuration interaction modeling of Si resonant exchange qubits for spin-photon coupling Samuel Quinn Future platforms for scalable quantum information processing, such as spin qubits, will require the capability to entangle qubits over long physical distances. A tantalizing proposal in this space is the capacity to couple triple-quantum-dot (TQD) spin qubits via a microwave resonator. This is possible in so-called “resonant exchange” (RX) voltage regimes, wherein the system possesses a non-vanishing transverse dipole moment, giving rise to a fast spin-photon coupling rate. In this talk, we detail how numerical simulations of such regimes using configuration interaction (CI) techniques reveal qualitative insights not captured in simpler models. In particular, we show how a distinct RX regime, which we term “XRX,” may be a good candidate for real-world TQD-resonator coupling [1]. Our results demonstrate how detailed modeling of the exact multi-electron wavefunctions is critical for realistic implementation of spin-photon coupling protocols, as well as exchange operation in general. |
Tuesday, March 15, 2022 9:24AM - 9:36AM |
F39.00006: Si/SiGe Single Spin Qubit Devices Enabled by Advanced Semiconductor Fabrication Lester F Lampert, Stephanie A Bojarski, Felix Borjans, Hubert C George, Eric M Henry, Roza Kotlyar, Florian Luthi, Samuel Neyens, Ravi Pillarisetty, Mick Ramsey, Simon Schaal, Thomas F Watson, Guoji Zheng, otto k zietz, Jeanette M Roberts, James S Clarke Reaching quantum practicality, where a quantum computer can solve useful problems, will likely require a million qubits. Semiconductor-based quantum computers can use advanced semiconductor manufacturing, making this a promising approach for scaling qubit count. But to take full advantage of this we need to take all the tools used to make massively scaled transistors devices and apply them to spin-qubit devices. However, quantum bits are more fragile than classical bits and require cryogenic systems for operation and testing. To enable the fast feedback methodology used in industry, the 300mm cryoprober was developed; it measures entire wafers at 1.6K. This tool allows down-selection of spin qubit devices for measurements in a dilution fridge and also provides critical feedback on fabrication processing. This has led to highly coherent Si/SiGe spin qubit devices fabricated using EUV lithography. Here, we'll discuss bringing high-volume tools and methods to the fabrication of spin qubit devices, including extending these to cryogenic temperatures. We observe well-controlled, stable, quantum dot devices with independent barrier control. Qubit control is achieved using EDSR with on-chip micromagnets. The results are reproducible on multiple devices and fridges. |
Tuesday, March 15, 2022 9:36AM - 9:48AM |
F39.00007: Electron-to-Nuclear Spectral Mapping via "Galton board" Dynamic Nuclear Polarization Arjun Pillai, Moniish Elanchezhian, Teemu Virtanen, Sophie Conti, Ashok Ajoy We report on a strategy to indirectly readout the spectrum of an electronic spin via polarization transfer to nuclear spins in its local environment. The nuclear spins are far more abundant and have longer lifetimes, allowing repeated polarization accumulation in them. Subsequent nuclear interrogation can reveal information about the electronic spectral density of states. We experimentally demonstrate the method for reading out the ESR spectrum of Nitrogen-Vacancy center electrons in diamond via readout of lattice 13C nuclei. Spin-lock control on the 13C nuclei yields significantly enhanced signal-to-noise for the nuclear readout. Spectrally mapped readout presents operational advantages in being background-free and immune to crystal orientation and optical scattering. We harness these advantages to demonstrate applications in underwater magnetometry. The physical basis for the “one-to-many” spectral map is itself intriguing. To uncover its origin, we develop a theoretical model that maps the system dynamics, involving traversal of a cascaded structure of Landau-Zener anti-crossings, to the operation of a tilted “Galton board”. This work points to new opportunities for “ESR-via-NMR” in dilute electronic systems, and in hybrid electron-nuclear quantum memories and sensors |
Tuesday, March 15, 2022 9:48AM - 10:00AM |
F39.00008: Tunable interdot coupling in SiMOS architectures over more than nine orders of magnitude Vivien Schmitt, Boris Brun-Barriere, Yann-Michel Niquet, Nicolas Piot, Simon Zihlmann, Xavier Jehl, Tristan Meunier, Maud Vinet, Romain Maurand, Silvano De Franceschi Silicon MOS and Silicon-Germanium heterostructures have been proven as a viable route for scalable solid-state quantum computing [1]. Single-qubits operation can routinely exceed 99% [2,3] and have coherence time exceeding few ms. For two-qubit gates, fidelities reaching 98% for electrons in Silicon have been shown [4], but the strength of the Heisenberg exchange interaction, mainly controlled by the tunnel rate between the two hosting dots, remains hard to control. |
Tuesday, March 15, 2022 10:00AM - 10:12AM |
F39.00009: Proposal for a cavity-mediated measurement of the exchange interaction in a triple quantum dot Florian Ginzel, Guido Burkard In spin qubit arrays the exchange coupling can be harnessed to implement two-qubit gates and to realize intermediate-range qubit connectivity along a spin bus. In this work, we propose a scheme to characterize the exchange coupling between electrons in adjacent quantum dots. We investigate theoretically the transmission of a microwave resonator coupled to a triple quantum dot occupied by two electrons. We assume that the right quantum dot (QD) is always occupied by one electron while the second electron can tunnel between the left and center QD. If the two electrons are in adjacent dots they interact via the exchange coupling. By means of exact analytical expressions we show that the transmission profile of the resonator directly reveals the value of the exchange coupling strength between two electrons. From perturbation theory up to second order we conclude that the exchange can still be identified in the presence of magnetic gradients. In case of a lifted valley degeneracy prior knowledge about the valley splitting and valley phase differences is important to correctly identify the transmission dips and thus the exchange coupling. |
Tuesday, March 15, 2022 10:12AM - 10:24AM |
F39.00010: Coupling Quantum Dots to 2DEG-Based Superconductor-Semiconductor Hybrids Alisa Danilenko, Andreas S Pöschl, Deividas Sabonis, Tyler Lindemann, Sergei Gronin, Geoffrey C Gardner, Candice Thomas, Michael J Manfra, Charles M Marcus We present experimental results for gate-defined lateral quantum dots coupled to a superconductor-semiconductor nanowire based on InAs/Al two-dimensional electron gas (2DEG). We demonstrate independent voltage control of coupling of multiple quantum dots to the superconducting wire on one side and normal semiconducting leads on the other. This provides experimental control of hybridization of discrete dot states to subgap Andreev states in the wire [1,2] and a tool for high-resolution spectroscopy of Andreev states [3], as well as a possibility to use the dots as filters [4]. A high degree of experimental control as well as extension to a variety of device geometries is made possible by the hybrid 2DEG platform. |
Tuesday, March 15, 2022 10:24AM - 10:36AM |
F39.00011: Theory of coherent spin transfer between two semiconductor quantum dots Jan A Krzywda, Lukasz Cywinski Long-distance transfer of quantum information in quantum dots (QDs) spin qubits will be necessary for their scalability [1]. One way of achieving this goal is to move the electron between tunnel-coupled QDs using a sweep of their energy detuning [2, 3]. We present here an analysis showing how coherent transfer of spin superposition is affected by electron-phonon scattering and charge noise in detuning and tunnel coupling at finite temperature. We have predicted that probability of charge transfer can be non-monotonic function of transfer time, and predicted that the error below 0.001 requires tunnel couplings above 20µeV, as it has been confirmed experimentally in Si/SiGe [3] and SiMOS [4]. Next we analyzed to what extent electron transfer modifies the spin coherence and uncovered that in absence of nuclear spins, main dephasing mechanisms are activated by a difference of Zeeman splittings in the QDs, which leads to: short-term creation of charge qubit and random phase rotation during temporal occupation of higher energy state. |
Tuesday, March 15, 2022 10:36AM - 10:48AM |
F39.00012: Coherent spin-valley oscillations in silicon Xinxin Cai, Elliot J Connors, John Nichol Electron spins in silicon quantum dots are excellent qubits because they have long coherence times, high gate fidelities, and are compatible with advanced semiconductor manufacturing techniques. The valley degree of freedom, which results from the specific character of the Si band structure, is a unique feature of electrons in Si spin qubits. However, the small difference in energy between different valley levels often poses a challenge for quantum computing in Si. Here, we show that the spin-valley coupling in Si, which enables transitions between states with different spin and valley quantum numbers, enables coherent electron-spin manipulation in Si. We demonstrate coherent manipulation of effective single- and two-electron spin states in a Si/SiGe double quantum dot without ac magnetic or electric fields. Our results illustrate that the valley degree of freedom, which is often regarded as an inconvenience, can itself enable quantum manipulation of electron spin states. |
Tuesday, March 15, 2022 10:48AM - 11:00AM Withdrawn |
F39.00013: Balancing coherent and dissipative dynamics in a central-spin system Bill Coish, Alessandro Ricottone, Yinan Fang The average time required for an open quantum system to reach a steady state (the steady-state time) is generally determined through a competition of coherent and incoherent (dissipative) dynamics. Here, we study this competition for a ubiquitous central-spin system, corresponding to a central-spin-1/2 coherently coupled to ancilla spins and undergoing dissipative spin relaxation. The ancilla system can describe N spins-1/2 or, equivalently, a single large spin of length I = N/2. We find exact analytical expressions for the steady-state time in terms of the dissipation rate, resulting in a minimal (optimal) steady-state time at an optimal value of the dissipation rate, according to a universal curve. Due to a collective-enhancement effect, the optimized steady-state time grows only logarithmically with increasing N = 2I, demonstrating that the system size can be grown substantially with only a moderate cost in steady-state time. This paper has direct applications to the rapid initialization of spin qubits in quantum dots or bound to donor impurities, to dynamic nuclear-spin polarization protocols, and may provide key intuition for the benefits of error-correction protocols in quantum annealing. |
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