Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session M39: Semiconductor Qubits VIFocus Recordings Available

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Sponsoring Units: DQI DCMP Chair: Guoji Zheng, Intel Corporation Room: McCormick Place W196A 
Wednesday, March 16, 2022 8:00AM  8:36AM 
M39.00001: Quantum state transfer in quantumdot spin chains Invited Speaker: John Nichol Electron spins in semiconductor quantum dots are a leading platform for quantum computing because they have extremely long coherence times and are compatible with advanced semiconductor manufacturing techniques. In recent years, largescale arrays of electron spins in gatedefined quantum dots have emerged as key elements of spinbased quantum information processors. Electron spin qubits naturally interact with each other via nearestneighbor exchange coupling. However, the ability to transmit quantum states over long distances is beneficial for faulttolerant quantum computing. In this talk, we discuss the experimental realization of various ways to transfer spin states in quantum dots and how such methods of state transfer might be useful for quantum computing. 
Wednesday, March 16, 2022 8:36AM  8:48AM 
M39.00002: Quantum simulation of Thouless pump on quantum hardware Xiao Xiao, Efekan Kokcu, James K Freericks, Alexander F Kemper We demonstrate the simulation of Thouless pump in a XY spin chain in the presence of staggered field on IonQ quantum hardware. The important ingredient of the Thouless pump is that the system should be evolving adiabatically. Therefore, the conventional quantum simulations based on Trotter decomposition would result in a circuit with large depth, which complicates achieving good results even for a short chain formed from several qubits. Here we map the original spin model to a free fermion model, which is identical to the RiceMele model, so that we can utilize a powerful compiling method to construct fixed depth circuits and simulate the Thouless pump with arbitrary small Trotter step. We show that with this technique, the clear features of Thouless pump can be identified on quantum hardware. 
Wednesday, March 16, 2022 8:48AM  9:00AM 
M39.00003: Collective coherent scattering from quantum dots in a photonic crystal waveguide Joel Q Grim, Ian Welland, Samuel G Carter, Allan S Bracker, Andrew L Yeats, Chul Soo Kim, Mijin Kim, Kha X Tran, Igor Vurgaftman, Thomas L Reinecke The lightmatter interface of a coherent field scattering from a quantum dot coupled to a nanophotonic waveguide enables efficient nonlinear photonphoton interactions and the realization of exotic states of light, such as twophoton bound states. The exploration of collective quantum phenomena with multiple dots within a waveguide is also of great interest, but the spectral inhomogeneity of quantum dots has been a persistent challenge. We overcome this inhomogeneity by straintuning InAs quantum dots into resonance, and experimentally demonstrate collective coherent scattering in a photonic crystal waveguide. We show that collective scattering results in an enhanced optical nonlinearity, demonstrated with both the intensity and photon statistics of transmitted coherent light. In addition to providing a means of manipulating quantum optical nonlinearities, collective coherent scattering in this platform may also allow the creation of highfidelity twoqubit gates, the study of nonMarkovian effects, and the creation of subradiant states. 
Wednesday, March 16, 2022 9:00AM  9:12AM 
M39.00004: Antisite defect qubits in monolayer transition metal dichalcogenides JengYuan Tsai, Jinbo Pan, Hsin Lin, Arun Bansil, Qimin Yan Quantum bit as the heart of quantum information technology brings unprecedented capability of computation that is expected to transform science and society in unimaginable ways. Being atomically thin and amendable to external controls, twodimensional (2D) materials offer a new paradigm for the realization of patterned qubit fabrication and operation at room temperature. Using highthroughput atomistic simulations and a symmetrybased hypothesis, we identify six neutral anionantisite defects in transition metal dichalcogenide (TMD) monolayers that host a paramagnetic triplet ground state. Our indepth analysis reveals the nature of optical transitions and tripletsinglet intersystem crossings in the qubit, which provides a complete cycle for initialization, manipulation and redout of the qubit. As an illustrative example, the operational principles of the antisite qubit in WS_{2} are discussed in details. We also demonstrate that the antisite defect qubit system is stable against interlayer interactions in a multilayer structure for qubit isolation and protection in future defectbased devices. The key characters of host materials that give rise to defects with a triplet ground state are discussed, which suggests a feasible strategy for continued discovery of promising defect qubits in diverse classes of 2D materials. Our study opens a new pathway for creating scalable and controllable spin qubits in 2D TMDs. 
Wednesday, March 16, 2022 9:12AM  9:24AM 
M39.00005: Alloptical Ramanbased noise spectroscopy of a solidstate spin Demitry Farfurnik, Harjot Singh, Zhouchen Luo, Allan S Bracker, Samuel G Carter, Robert M Pettit, Edo Waks The development of spin qubits with long coherence times for quantum information processing, communication and sensing requires sources of spin noise to be identified and mitigated. Although microwavebased spin control is typically used for noise spectroscopy of solidstate spin qubits, this approach becomes infeasible when high frequency noise components are stronger than the available microwave powers. Here, we introduce an alloptical approach for noise spectroscopy of spin qubits, which enables the characterization of spin systems for which microwave control is challenging. Our approach involves Ramanbased spin rotations to optically implement the CarrPurcellMeiboomGill pulse sequences inspired by nuclear magnetic resonance spectroscopy. Analyzing the temporal dynamics of a spin of interest under the application of these sequences allows us to extract the spectral densities of the noise sources that interact with the spin and lead to its decoherence. To demonstrate the capabilities of our alloptical approach for noise spectroscopy, we use it to measure the noise spectral density of a single spin confined in an InAs/GaAs quantum dot. By leveraging the high bandwidths (over 100 MHz) provided by the alloptical approach, we extract the high frequency spectral density of the noise of a single spin interacting with a large ensemble of nuclear spins broadened by strain. Our measurements confirm previous theoretical modeling of such hyperfine interactions, and shed light on the ability to extend quantum dot coherence times utilizing dynamical decoupling sequences. As such, our Ramanbased approach for noise spectroscopy provides insights for the development of opticallyactive semiconductor spin qubits with long coherence times for quantum information processing, communication and sensing. 
Wednesday, March 16, 2022 9:24AM  9:36AM 
M39.00006: Spin response in selfassembled quantum dots beyond the gtensor model Arthur Lin, Garnett W Bryant Selfassembled quantum dots, with both electrical tunability and optical addressability, have shown promise as a semiconductor qubit architecture. The use of hole spins as qubit basis increases lifetime for weak nuclear interactions. Furthermore, hole spins in selfassembled dot have strong spinorbit interactions, which we seek to utilize as a control scheme. In this talk, we discuss the interplay of spinorbit effects and higher order magnetic fields terms. The resulting effects, such as atomiclevel spin texture, cannot be fully captured by existing gtensor models. As such, we propose second order diamagnetic corrections to the linear gtensor model. We compare the corrected model to a fully atomistic tightbinding model to show experimentally realizable regimes of said corrections. Finally, we have a brief discussion of double dot systems and alloyed systems, which exhibit a much stronger diamagnetic shift. 
Wednesday, March 16, 2022 9:36AM  9:48AM 
M39.00007: Quantum Simulation of Quantized Plasmons in 1D Systems: The critical role of onsite repulsion and Coulomb exchange Garnett W Bryant, Emily Townsend Linear atomic chains, such as atom chains on surfaces, linear arrays of dopant atoms in semiconductors, or linear molecules, provide ideal testbeds for studying singleparticle, collective (plasmonic) and strongly correlated excitations in the quantum limit for interacting matter systems. We use exact diagonalization to find the manybody excitations of finite (426) atom chains, including hopping, longrange electronelectron repulsion and the corresponding electroncore attraction in an extendedrange Hubbard model. For spinless electrons, we showed previously that quantized plasmonic excitations can be identified in chains as short as 8 atoms and can be launched onebyone by quantum emitters attached to the chain. When spin is included, we find that quantized plasmons still can exist in short chains for a wide range of onsite repulsion of opposite spins U. However, for U large enough that the same spins cluster locally, the excitations cease to be plasmonic. Short range Coulomb exchange also plays a key role. Quantized plasmonic excitations disappear in the absence of this exchange. Systems with and without spin will be compared to highlight the essential physics that determines the quantization of 1D excitations in each regime. 
Wednesday, March 16, 2022 9:48AM  10:00AM 
M39.00008: LiebRobinson correlation functions in 1D, 2D, and 3D qubit networks Craig S Lent, Brendan J Mahoney The LiebRobinson correlation function provides a stateindependent measure of quantum entanglement between two qubits. An important and wellknown result is that this quantum correlation between qubits is local and its spatial spread in a network of interacting qubits is limited by a finite velocity, the LiebRobinson velocity. We consider qubits inspired by quantumdot cellular automata whose parameters can be electronically tuned. The resulting Hamiltonian is of the transversefield Ising model form, which has been realized in multiple systems including superconducting qubit arrays. Our focus is on the earlytime behavior which grows with a powerlaw dependence on time. The powerlaw exponent increases linearly with distancehere characterized by the number of interacting qubit links connecting the two correlated qubits. We deduce an analytic form for the earlytime correlation function for a network of qubits with arbitrary connectivity in one, two, and three dimensions. For regular square arrays we calculate the dependence of the LiebRobinson velocity on the direction of propagation. 
Wednesday, March 16, 2022 10:00AM  10:12AM 
M39.00009: Spin qubits in carbon nanotubes Matthieu Desjardins, Quentin Schaeverbeke, Sergio De Bonis, Arthur Larrouy, Benoit Neukelmans, Louis Virey, Davide Stefani, Maria El Abassi, Joey Sulpizio, Matthieu Delbecq, Gulbostan Albulizi, Jeanne Becdelievere, Takis Kontos Spin qubits hosted in carbon nanotubes is a promising scalable platform for high fidelity qubits. Carbon nanotubes can be interfaced with onchip microwave circuits [1] and the electronic spin of a double quantum dots coupled to microwave photon [2,3,4,5]. I will present the decoherence mechanisms associated to the hybrid chargespin spectrum [6] and give their estimation in the case of suspended carbon nanotubes. 
Wednesday, March 16, 2022 10:12AM  10:24AM 
M39.00010: Polaron effects on optical properties of semiconductor based spinphoton interfaces Mona I Berciu, Jeff F Young, Leonard Ruocco Understanding the effects of vibrational modes on solidstate quantum bits proves a major challenge in developing robust spinphoton interfaces for semiconductor quantum computing architectures. Donor spins in silicon are known to exhibit remarkably longcoherence times making them attractive candidates for qubits, however the semiconductor environment introduces strong electronphonon couplings which adversely effect the fidelity of the spinphoton interface, and therefore our ability to entangle qubits and perform quantum gate computations. In order to better understand the role of electronphonon couplings in these systems, we study a microscopic model that captures the physical mechanisms inherent to these interactions in indirect bandgap semiconductors like silicon. In particular, we focus on the role played by nonlocal electronphonon couplings which we find to have a substantial effect on the calculated lifetimes of the optical transitions pertaining to the donor atoms. We report on calculated fluorescence emission spectra that closely resemble phonon sideband formation and zerophonon line characteristics in experimentally observed spectra, as well as identifing the physical mechanisms by which nonlocal electronphonon couplings lead to zerophonon line broadening. 
Wednesday, March 16, 2022 10:24AM  10:36AM 
M39.00011: Quantum Information Scrambling in Extended Hubbard Models Nikolaos Petropoulos This study investigates entanglement and quantum information scrambling (QIS) by the example 
Wednesday, March 16, 2022 10:36AM  10:48AM 
M39.00012: Tailoring Quantum Oscillations of Excitonic Schrodinger’s Cats as Qubits Shouvik Datta, Amit Bhunia, Mohit K Singh, Mohamed Henini, Maryam Al Huwayz We report [https://arxiv.org/abs/2107.13518] experimental detection and control of Schrodinger’s Cat like macroscopically large, quantum coherent state of a twocomponent BoseEinstein condensate of spatially indirect electronhole pairs or excitons. Phase coherent periodic oscillations in photo generated capacitance as a function of applied voltage bias and light intensity over a macroscopically large area are measured. Coherent resonant tunneling in this welldot heterostructure restricts the available momentum space of the charge carriers within this quantum well. Consequently, the average electric polarization vector of the associated indirect excitons collectively orients along the direction of applied bias and these excitons undergo BoseEinstein condensation below ~100 K. Finally, we observe collective Rabi oscillations of these macroscopically large, ‘multipartite’, twolevel, coupled and uncoupled quantum states of excitonic condensate as qubits. Moreover, some of these excitons undergoing BEC can be addressed independently of others using applied bias over a localized region to satisfy, in principle, the DiVincenzo’s criteria for scalable quantum computation. 
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