Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session S36: Spin Qubit Measurement IFocus Recordings Available

Hide Abstracts 
Sponsoring Units: DQI Chair: Thomas Watson, Intel Room: McCormick Place W194A 
Thursday, March 17, 2022 8:00AM  8:12AM 
S36.00001: Theoretical Constructions of ExchangeOnly Entangling and Leakage Control Gates Thaddeus D Ladd It was first shown 22 years ago that composite sequences of exchange pulses generated by computational searching and algorithmic optimization methods allow universal control over qubits encoded in decoherencefree subsystems (DFS) [1]. It was shown 11 years ago, again via computational search, that such control may be done more efficiently and without spinpolarization [2]. In the past decade, increased theoretical understanding of these control strategies have allowed analytic understanding and minimumresourcetheorems for these sequences [3]. This understanding has also yielded tools to derive new sequences which mitigate the spread of leakage out of the DFS, with utility in facilitating quantum error correction. Experiments in arrays of 6 Si/SiGe dots are starting to prove these constructions practical and performant [4,5]. This talk will provide theoretical constructions for exchangegatesynthesis useful for both analytic and computational derivation of new control pathways. I will provide logical understanding of some previous computergenerated sequences [2,6]. Finally, I will provide examples of new leakagemitigation strategies, with brief indication of their experimental implementation and performance expectations in silicon. 
Thursday, March 17, 2022 8:12AM  8:24AM 
S36.00002: Symmetry Protected Entanglement Hassan Shapourian, Kasra Hejazi Symmetry is an important property of quantum mechanical systems which may dramatically influence their behavior in and out of equilibrium. In this talk, we study the effect of symmetry on tripartite entanglement properties of typical states in symmetric sectors of Hilbert space. In particular, we consider Abelian symmetries and derive explicit expression for the logarithmic entanglement negativity of systems with $\mathbb{Z}_N$ and $U(1)$ symmetry groups. To this end, we develop a diagrammatic method to incorporate partial transpose within random matrix theory of symmetric states and formulate a perturbation theory in the inverse of the Hilbert space dimension. We further present entanglement phase diagrams as the subsystem sizes are varied and show that there are qualitative differences between systems with and without symmetries. 
Thursday, March 17, 2022 8:24AM  8:36AM 
S36.00003: Latched readout for the semiconductor quantum dot hybrid qubit Sanghyeok Park, Joelle J Corrigan, John P Dodson, Brandur Thorgrimsson, Samuel Neyens, Trevor Knapp, Thomas W McJunkin, Sue N Coppersmith, Mark A Eriksson We explain and demonstrate a latched readout scheme for the semiconductor quantum dot hybrid qubit (QDHQ), working at the 5electron (4,1)(3,2) charge configuration. This configuration enables latching into either the (3,1) or the (4,2) charge states which can be detected with timeaveraged or singleshot measurement. Here we demonstrate a singleshot measurement fidelity of 90.2% achieved using only a single electron reservoir for the doublequantumdot pair; this will become increasingly important when scaling to larger arrays. We also show that the 5electron QDHQ has an improved readout window in gate voltage space when compared with the 3electron QDHQ, which is sometimes limited by small valley splitting in Si/SiGe heterostructures. This combination of latched readout and an enhanced readout window in gate voltage space makes the 5electron QDHQ a promising semiconductor quantum dot qubit with fast manipulation and a relatively long coherence time. 
Thursday, March 17, 2022 8:36AM  9:12AM 
S36.00004: Operation of quantum dot spin qubits at elevated temperatures Invited Speaker: Arne Laucht Quantum computers are expected to outperform conventional computers for a range of important problems, from molecular simulation to search algorithms, once they can be scaled up to large numbers of quantum bits (qubits), typically millions. Spin qubits in silicon MOS quantum dots are one of the big contenders for a scalable, solid statebased quantum computing platform. Here, the qubits are encoded as the spin states of individual electrons confined in electrostaticallygated quantum dots. The great potential of this system has been demonstrated through various experiments over the last few years, with coherence times of up to T_{2}=28 ms, single qubit control fidelities of 99.96%, and twoqubit control fidelities of 98%. 
Thursday, March 17, 2022 9:12AM  9:24AM 
S36.00005: Highfidelity single spinqubit control with an Inteldeveloped AWG Florian Luthi, Felix F Borjans, Nader Khammassi, Robert Flory, Linda Patricia Osuna Ibarra, Adrian Cardoza, Satoshi Suzuki, Ritika Sharma, Eric M Henry, Hubert C George, Lester F Lampert, Ravi Pillarisetty, Stephanie A Bojarski, Jeanette M Roberts, James S Clarke Quantum computing promises to tackle exciting and computationally difficult problems. Intel is leveraging 50 years of experience in semiconductor manufacturing to develop siliconbased spin qubit devices. Whereas the electrons, whose spin states are used as qubit states, are all identical, their surroundings are not. Hence, precise calibration of the signals controlling the qubits is required. Moreover, spin qubits require multiple voltage control lines per qubit, plus potentially shared microwave control lines. To orchestrate these increasingly complex setups, we use an inhouse developed control and calibration software. It allows us to produce hardware agnostic pulse sequences that are interpreted by the control electronics. In particular, we demonstrate that an inhouse developed arbitrary waveform generator (AWG), which relies on direct digital synthesis to translate instructions into precisely timesd pulses (arbitrary waveforms), is a useful tool for coherent qubit control. Leveraging the AWG’s high instruction bandwidth (upload speed), coupled with a large memory, we achieve singlequbit randomized benchmarking fidelities approaching 99.9% in a natural Silicon sample. 
Thursday, March 17, 2022 9:24AM  9:36AM 
S36.00006: Impact of phononmeditated backaction in SiGe spin qubits Rex O Lundgren, Charles Tahan Phonons emitted by semiconducting spin qubit read out devices, such as quantum point contacts or single electron transistors, can be coherently absorbed by the qubit leading to backaction effects. For example, it was experimentally demonstrated that phonons emitted by a quantum point contact can modify the charge stability diagram of a GaAs spin qubit [1]. More specifically, the absorption of the phonons lead to oscillations in the probability of being in different charge states, which produced observable ripples in the charge stability diagram. In this work, we theoretically extend the work of Ref. [1] to a SiGe spin qubit which is readout by a single electron transistor. Using various analytical methods, including Keldysh field theory, we discuss how the charge stability diagram is impacted by the coherent absorption of phonons emitted by the single electron transistor and similarities and differences with the results presented in Ref. [1] for GaAs. We then move beyond a single qubit and investigate how twoqubit gate fidelity is impacted by this phononmediated backaction process. 
Thursday, March 17, 2022 9:36AM  9:48AM 
S36.00007: Dispersive RF Measurement of a Tip Induced Quantum Dot in a mKSTM Jonathan J Marbey, Michael Dreyer, YunPil Shim, Robert E Butera The development of devicebased semiconductor spin qubits is an inherently challenging, multifaceted effort. Such an endeavor requires significant materials overhead coupled with complex, multilayered fabrication processes before any measurement can even take place. This workflow is further complicated when exploring new materials with the goal of determining suitability for implementation in devices. Here, we seek to circumvent the barriers imposed by device fabrication and instead probe semiconducting materials directly via radio frequency (RF) reflectometry combined with a millikelvin scanning tunneling microscope (mKSTM). In this configuration, STM tip induced band bending gives rise to the formation of a quantum dot which can be scanned across a sample surface as a means to study interactions with surrounding defects. Meanwhile, the dispersive RF measurement provided by an integrated LCtank circuit permits the determination of specific dot properties, including charge occupation and size. As a demonstration of this capability, we present spectroscopic measurements on chlorineterminated silicon wafers of various doping levels, in which the STM tipsample bias is swept while small shifts in the tank circuit resonance, due to changes in quantum capacitance, are recorded. The techniques described herein will be extended to more complicated heterostructure materials, while also providing a pathway for nondestructive characterization of semiconductor materials for quantum information science applications. 
Thursday, March 17, 2022 9:48AM  10:00AM 
S36.00008: Hybrid academic/industrial silicon spin qubit devices for spin readout and manipulation Bernhard Klemt, Bruna C Paz, Cameron Spence, Victor ElHomsy, Vivien Thiney, Renan Lethiecq, David J Niegemann, Emmanuel Chanrion, Baptiste Jadot, PierreAndré Mortemousque, Benoit Bertrand, Thomas Bédécarrats, Heimanu Niebojewski, Romain Maurand, Silvano De Franceschi, Maud Vinet, Tristan Meunier, Matias Urdampilleta Silicon based spin qubits are among the leading candidates for a scalable quantum computer. To unveil their full potential regarding scalability and cointegration with classical electronics, these devices have to be fabricated in a ComplementaryMetalOxideSemiconductor (CMOS) process. 
Thursday, March 17, 2022 10:00AM  10:12AM 
S36.00009: High Fidelity Spin Readout in a CMOS Device David J Niegemann, Emmanuel Chanrion, Baptiste Jadot, Bernhard Klemt, Victor ElHomsy, Bruna C Paz, PierreAndré Mortemousque, Benoit Bertrand, Romain Maurand, Silvano De Franceschi, Maud Vinet, Franck Balestro, Tristan Meunier, Matias Urdampilleta Following Moore’s law, CMOS electronics is approaching feature sizes of a few nm. At this size, quantum effects become important, posing challenges to classical computer architecture, while creating new research opportunities for quantum information processing. 
Thursday, March 17, 2022 10:12AM  10:24AM 
S36.00010: Electrostatic coupling control of twogate metal levels CMOSbased quantum dots Bruna C Paz, Victor ElHomsy, David J Niegemann, Bernhard Klemt, Emmanuel Chanrion, Vivien Thiney, Baptiste Jadot, PierreAndré Mortemousque, Benoit Bertrand, Thomas Bédécarrats, Heimanu Niebojewski, François Perruchot, Silvano De Franceschi, Maud Vinet, Matias Urdampilleta, Tristan Meunier Recent demonstrations of highfidelity gates using CMOSbased silicon quantum dots (QDs) have boosted the interest of the semiconductor industry to extend their applications to quantum computing. The importance of having individual control of the QD chemical potential and its coupling interactions (QDQD and QDreservoir) motivated the development of different architectures with increased number of metal levels. 
Thursday, March 17, 2022 10:24AM  10:36AM 
S36.00011: Dispersively Probed Microwave Spectroscopy of a Silicon Hole Double Quantum Dot Simon Zihlmann, Rami Ezzouch, Vincent Michal, Jing Li, Agostino Apra, Benoit Bertrand, Louis Hutin, Maud Vinet, Matias Urdampilleta, Tristan Meunier, Xavier Jehl, YannMichel Niquet, Silvano De Franceschi, Romain Maurand Owing to ever increasing gate fidelities and to a potential transferability to industrial CMOS technology, silicon spin qubits have become a compelling option in the strive for quantum computation. In a scalable architecture, each spin qubit will have to be finely tuned and its operating conditions accurately determined. In view of this, spectroscopic tools compatible with a scalable device layout are of primary importance. 
Thursday, March 17, 2022 10:36AM  10:48AM 
S36.00012: Dispersive Sensing of Holes in Silicon Fin FieldEffect Transistors Rafael S Eggli, Taras Patlatiuk, Leon Camenzind, Simon Geyer, Deepankar Sarmah, Jann H Ungerer, Roy Haller, Christian Schonenberger, Richard J Warburton, Dominik M Zumbuhl, Andreas V Kuhlmann Silicon is a promising host material for quantum dot (QD) spin qubits, offering long coherence and short gate times. Moreover, a scalable array of densely packed qubits can be envisaged by leveraging wellestablished industry standard finfieldeffect transistor (FinFET) technology. Recently, a hole spin qubit in FinFETs operating at 4.2K was demonstrated, showcasing fast, allelectrical qubit control [Camenzind et al. arXiv:2103.07369]. The small device footprint and high operation temperature are crucial for future scaling. Here, we report on gatebased reflectometry of holecharge transitions in QDs formed in FinFET devices. For this purpose, a tank circuit on a dotdefining gate is probed resonantly. Tunnelling of holes in the vicinity of the gate alters the gate admittance that causes a dispersive shift of the reflected signal. Varactor diodes are integrated to tune impedance matching [Ares et al. PRA 5, 034011 (2016)]. We benchmark the resonator performance of commercial inductors as well as superconducting thinfilm NbTiN inductors. Our results pave the way towards fast, singleshot readout of FinFET hole spin qubits at fewkelvin temperatures. 
Follow Us 
Engage
Become an APS Member 
My APS
Renew Membership 
Information for 
About APSThe American Physical Society (APS) is a nonprofit membership organization working to advance the knowledge of physics. 
© 2022 American Physical Society
 All rights reserved  Terms of Use
 Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 207403844
(301) 2093200
Editorial Office
1 Research Road, Ridge, NY 119612701
(631) 5914000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 200452001
(202) 6628700