Bulletin of the American Physical Society
2023 APS March Meeting
Volume 68, Number 3
Las Vegas, Nevada (March 510)
Virtual (March 2022); Time Zone: Pacific Time
Session S74: Semiconducting Qubits IIFocus

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Sponsoring Units: DQI Chair: Ferdinand Kuemmeth, Niels Bohr Institute, University of Copenhagen Room: Room 403/404 
Thursday, March 9, 2023 8:00AM  8:36AM 
S74.00001: Quantum computation with hole spin qubits in Si and Ge quantum dots. Invited Speaker: Stefano Bosco Hole spin qubits in silicon and germanium quantum dots are promising platforms for quantum computing because of their large spinorbit interactions, permitting efficient and ultrafast allelectric qubit control. 
Thursday, March 9, 2023 8:36AM  8:48AM 
S74.00002: Influence of charge noise on foundryfabricated spin qubit Victor ElHomsy, Bernhard Klemt, Vivien Thiney, Renan Lethiecq, Cameron Spence, Bruna CardosoPaz, Emmanuel Chanrion, David J Niegemann, Pierre A Mortemousque, Baptiste Jadot, Benoit Bertrand, Heimanu Niebojewski, Christopher Bäuerle, Maud Vinet, YannMichel Niquet, Tristan Meunier, Matias Urdampilleta Semiconductor quantum dots represent a promising platform for quantum information processing [1]. Among the various technologies belonging to this category, silicon has lowspinorbit interaction, and can be purified into its zero nuclear spin isotopes. Electron spins in silicon therefore stand out as potential qubits given their long coherence times and demonstrated faulttolerant single qubit operations [2]. In this context, quantum dots (QDs) formed in CMOS classical electronics offer a path towards scalable quantum computing, by leveraging industrial fabrication foundries [3], and potentially make reliable spin qubits 
Thursday, March 9, 2023 8:48AM  9:00AM 
S74.00003: Si/SiGe quantum devices with full 300mm process Clement Godfrin, Asser Elsayed, Mohamed Shehata, Ruoyu Li, George Simion, Stefan Kubicek, Shana Massar, Yann Canvel, Julien Jussot, Roger Loo, Andriy Hikavyy, Massimo Mongillo, Danny Wan, Kristiaan De Greve Spin qubits in silicon have been considered as one of the most promising candidates for large scale quantum computers due to their long coherence, highfidelity and compatibility with CMOS technology.? In Si/SiGe devices, the electrons are confined at the highquality crystalline interface, which reduces potential disorders and decreases charge noises, making it a very promising platform for qubit array upscaling. However, some challenges remain with the SiGe heterostructure, among which higher trapping density at the upper SiGe interface, crystalline dislocation, low valleysplitting. 
Thursday, March 9, 2023 9:00AM  9:12AM 
S74.00004: Temperature scaling of spin qubit performance in Si/SiGe quantum dots Oriol PietxCasas, Eline Raymenants, Brennan Undseth, Lieven M Vandersypen, Giordano Scappucci, Mateusz T Madzik, Stephan G Philips, Sergey V Amitonov, Amir Sammak Gatebased accumulation devices for quantum information processing are usually operated in the 20mK regime, where charge noise is minimized and phonon processes are almost negligible. In recent years, operation at higher temperatures has gained interest in the community since operating at >1.6K unlocks simpler and more powerful cooling systems, ideal for cointegration with the necessary control electronics. We present the performance of our standard ^{28}Si/SiGe devices [1] as the temperature is increased, a platform yet to be shown at higher temperatures. We report the effects of temperature on singlequbit timescales (T_{1}, T_{2}^{*}, T_{2}^{H}, T_{2}^{CPMG}) and during PSB readout. Additionally, we measure noise at the sensors and qubits. We inspect the temperature response in the 200mK – 850mK regime, limited by readout visibility. Results across the qubit array show: (i) T_{1} scaling better behaved than [2] predicts, (ii) T_{2}^{*} almost flat, with temperature increase and (iii) whitening of the noise spectrum at high frequencies. All in all the device shows remarkable prospects for temperature scaling, especially considering that the heterostructure is not optimized for these temperatures. 
Thursday, March 9, 2023 9:12AM  9:24AM 
S74.00005: Heating effects and frequency shifts in a sixqubit Si/SiGe quantum processor Brennan Undseth, Oriol PietxCasas, Eline Raymenants, Mohammad Mehmandoost, Mateusz T M?dzik, Stephan G Philips, Sergey V Amitonov, Sander L de Snoo, Larysa Tryputen, Amir Sammak, Giordano Scappucci, Lieven M Vandersypen As spinbased quantum processors grow in size and complexity, maintaining high fidelities and minimizing crosstalk will be essential for the successful implementation of quantum algorithms and errorcorrection protocols. In particular, recent experiments have highlighted pernicious transient qubit frequency shifts associated with microwave qubit control. Workarounds for small devices, including prepulsing with an offresonant microwave burst to bring a device to a steadystate, wait times prior to measurement, and qubitspecific calibrations all bode ill for device scalability. Here, we make substantial progress in understanding and overcoming this effect. First, in a sixqubit silicon quantum processor, we report a surprising nonmonotonic relation between device temperature and qubit frequency, with frequency shifts of a similar magnitude as those induced by microwave driving. Possible mechanisms are discussed. Second, we evaluate the robustness of rfreflectometry in the context of heating. Last, we find a pragmatic solution to the heating effect: raising the device operating temperature to about 200 mK. We show this leads to stable qubit frequencies and eliminates the need for prepulsing and wait times without compromising qubit coherence. 
Thursday, March 9, 2023 9:24AM  9:36AM 
S74.00006: An analysis of spin orbit effects on spin dependent tunnel coupling and gfactor tuning in double quantum dots Arthur Lin, Garnett W Bryant Selfassembled quantum dots have been sought as semiconductor qubit architecture due to their optical addressability and electrical tunability. Double dot systems have the additional tunability of electrically biasing the two dots in and out of energetic resonance. During resonance, the tunnel coupling strength between the two dots depends on the orientation of the spin state, which, in turn, modifies the effective gfactor of the states. The physical mechanism driving spindependent tunneling and the change in effective gfactor has not been well studied. We present results obtained with an atomistic tightbinding model and perturbative analysis of the tightbinding wavefunctions to show that the change in gfactor during resonance arises solely from inclusion of the Peierls contribution. In contrast, the other two magnetic field terms, namely, the spin and atomic orbital contributions do not contribute to the resonance behavior of the gfactor or exhibit and other resonance behavior. Additionally, we contrast electron and holes states, with and without spinorbit terms in the Hamiltonian, to demonstrate the spinorbit nature of resonance gfactor tuning. 
Thursday, March 9, 2023 9:36AM  9:48AM 
S74.00007: Integrating Si/SiGe quantum devices with onchip classical circuitry Michael Wolfe, Thomas W McJunkin, Daniel R Ward, Deanna M Campbell, Lisa A Tracy, Mark Friesen, Mark A Eriksson The rapid acceleration of quantum computing technologies is poised to reach an interconnect bottleneck, where the qubit count in a quantum processor is limited by the number of inputoutput (I/O) connections. We demonstrate the operation of an onchip classical multiplexer on an array of Si/SiGe quantum Hall devices that reduces the I/O connections on the chip by nearly ten fold, with a Rent exponent p = 0. We use the Hall devices to characterize the performance of the integrated switches at 2K and high magnetic fields. We measure the signal bandwidth through the multiplexing circuit and discuss a protocol for multiplexed chargesensing readout of quantumdot qubits equipped with this technology. We discuss the impact of the finite bandwidth on singleshot readout fidelity for an array of N quantum dot charge sensors. 
Thursday, March 9, 2023 9:48AM  10:00AM 
S74.00008: Coherent Conveyor Mode Shuttling of Electrons and their Spin Tom Struck, Lino Visser, Ran Xue, Hendrik Bluhm, Lars Schreiber One and twoqubit manipulation fidelity has been increased to the point at which quantum error correction is possible, if the qubit platform becomes scalable. 
Thursday, March 9, 2023 10:00AM  10:12AM 
S74.00009: A scalable spinshuttling architecture for Si/SiGebased quantum computing Alexander Willmes, Matthias Künne, Harsh Bhardwaj, Max Oberländer, Julian Teske, Ran Xue, Inga Seidler, Eugen Kammerloher, Lars Schreiber, Hendrik Bluhm Si/SiGe spinqubits recently achieved operational fidelities above the error threshold for quantum error correction schemes, shifting the focus to increasing qubit numbers. A viable architecture for a quantum processor needs to provide solutions for scalingup in two dimensions while providing enough space for control lines and potentially locally integrated control electronics. 
Thursday, March 9, 2023 10:12AM  10:24AM 
S74.00010: Impact of phonons on Si/SiGe spin qubits Rex O Lundgren, Matthew Brooks, Charles Tahan We theoretically investigate how phonons impact the fidelities of semiconductor spin qubit gate operations as a function of several parameters, including temperature, confinement length, and interdot distance. We consider both LossDiVincenzo and singlettriplet Si/SiGe spin qubits and use a master equation based approach to investigate phononinduced errors, including leakage outside the computational subspace. Phonons generated by spin qubit readout devices also impact the fidelities of semiconductor spin qubit gate operations. Here, we theoretically explore how phonons emitted from a single electron transistor impact LossDiVincenzo and singlettriplet Si/SiGe spin qubit gate operations using several analytical approaches, including Keldysh field theory. 
Thursday, March 9, 2023 10:24AM  10:36AM 
S74.00011: Electrostatic uniformity and twodimensional quantum dot arrays in silicon Marcel Meyer, Florian K Unseld, Corentin Déprez, Timo R van Abswoude, Dingshan Liu, ChienAn Wang, Mateusz T M?dzik, Saurabh Karwal, Stefan Oosterhout, Sergey V Amitonov, Larysa Tryputen, Francesco Borsoi, Amir Sammak, Nico Hendrickx, Giordano Scappucci, Lieven M Vandersypen, Menno Veldhorst Engineering highly uniform twodimensional quantum dot arrays might be an essential requirement for building a scalable quantum processor based on silicon spin qubits. Here we show tuneable tunnel couplings in a silicon 2x2 quantum dot array operated in the single electron regime. In such a device we can compensate fluctuations in the electrostatic environment by applying individual gate voltages for each quantum dot. However, scaling this approach to larger arrays would lead to excessive overheads in tuning and control electronics. Therefore, we developed a method to electrically increase the potential uniformity in heterostructure quantum wells. We demonstrate that pinchoff voltages in quantum dot devices can be tuned over hundreds of millivolts and that they remain stable for hours afterward. Applying our method, we homogenize the pinchoff voltages of the plunger gates in a linear array for four quantum dots and reduce their spread by one order of magnitude. This work offers a new tool for the tuning of spin qubit devices providing perspectives for the implementation of scalable spin qubit arrays. 
Thursday, March 9, 2023 10:36AM  10:48AM 
S74.00012: Characterization of Silicon based Charge and Spin qubits in a 22nm Commercial FDSOI Process IMRAN BASHIR, Dirk R Leipold, Elena Blokhina, Mike Asker, Andrii Sokolov, Conor Mcgeough, Panagiotis Giounanlis, Conor Power, Xutong Wu, Dennis AndradeMiceli, Eoghan O'Shea The monolithic integration of the semiconductor qubit array and its associated classic control circuitry manufactured in a commercial CMOS foundry process is a key enabler of a scalable quantum processor with thousands of Qubits as an alternative to superconducting structures. As a result, the highly integrated single chip solution provides greater flexibility in design space due to the simplified and seamless control interface and low thermal budget compared to a multichip solution where the cryogenic control and qubit substrate are placed at different temperature stages in a cryocooler. While the superiority of analog and digital signal processing of CMOS transistors in Si substrate operating at cryogenic temperatures has been established, the impact on qubit fidelity in a commercial CMOS process has to be understood. In this work, we present our latest measurement results on charge and spin qubits in a double and triple quantum dot structure fabricated in a fully depleted silicononinsulator (FDSOI) process from GlobalFoundries at 3.5K. Based on those results, broader projections and implications on qubit technology and the viability of quantum error correction will be discussed. 
Thursday, March 9, 2023 10:48AM  11:00AM 
S74.00013: Semiconducting qubits with embedded control and readout cryoCMOS circuits Baptiste Jadot, Marcos Zurita, Gérard Billiot, Yvain Thonnart, Loïck Le Guevel, Mathieu Darnas, Candice Thomas, Jean Charbonnier, Tristan Meunier, Maud Vinet, Franck Badets, Gaël Pillonnet The scaling of quantum nanoprocessors requires the development of integrated electronics as close as possible of the quantum chips. In this context, electron spin qubits in semiconductors have been identified as a promising platform due to both its long coherence time and the possibility to leverage the wellestablished fabrication of microelectronic foundries for Si based quantum devices. Their direct compatibility with CMOS electronics would enable a cointegration in a compact manner of quantum devices and control electronics. Studying the compatibility between these two fields is necessary to increase the size of quantum computing arrays beyond a few qubits and solve the connectivity bottleneck. 
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