Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session K39: Semiconductor Qubits VFocus Recordings Available

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Sponsoring Units: DQI DCMP Chair: Guido Burkard, Konstanz Room: McCormick Place W196A 
Tuesday, March 15, 2022 3:00PM  3:36PM 
K39.00001: Phase correction code on spin qubits Invited Speaker: Floor Van Riggelen An important requirement for realizing a useful quantum computer are large numbers of faulttolerant qubits. Spin qubits, based on quantum dots in semiconductor materials such as silicon and germanium, are a promising platform because they resemble transistors and therefore have great potential for scalability. However, implementing error correction codes, to achieve fault tolerance, have not been shown on spin qubits yet. 
Tuesday, March 15, 2022 3:36PM  3:48PM 
K39.00002: Exchange gate between hole spin qubits with Rashba spinorbit coupling YunPil Shim, Omadillo Abdurazakov, Charles Tahan Hole spin qubits in semiconductor quantum dots have seen rapid progress in recent years. We focus on the Rashba spinorbit (SO) coupling, which has been used to implement electric dipole spin resonance (EDSR) without microstructures to create local magnetic fields for singlequbit gate operations. We theoretically study the exchange interaction between localized holes in a double quantum dot system in the planar semiconductor heterostructure, elucidating the effects of the Rashba spinorbit coupling. Effective Hamiltonian of the system and optimal conditions for twoqubit gates based on the exchange interaction between hole spin qubits with the SO coupling are presented. 
Tuesday, March 15, 2022 3:48PM  4:00PM 
K39.00003: A single hole spin with enhanced coherence in natural silicon Nicolas Piot, Boris BrunBarriere, Vivien Schmitt, Simon Zihlmann, Vincent Michal, YannMichel Niquet, Agostino Apra, Xavier Jehl, Benoit Bertrand, Tristan Meunier, Maud Vinet, Romain Maurand, Silvano De Franceschi Spin quantum bits in semiconductor appear to be one of the most promising technologies for the development of the quantum processor. Although electrons are the focus of modern research, holes exhibit many interesting physical properties. In particular, spinorbit interaction allows a fully electrical control of the hole spin qubit state. As a drawback, any external electric perturbation is likely to induce decoherence. Here we demonstrate for a single hole qubit in silicon the existence of sweet spots at which the qubit is decoupled from charge noise while keeping an efficient electrical driving. We first realize spin singleshot readout of the first hole accumulated in a natural silicon quantum dot made from an semiindustrial 300mm CMOS foundry. Subsequently, we characterize the hole spin gtensor and its susceptibility to electric fields by coherent manipulation depending on the external magnetic field orientation. It reveals optimal operation points at which the longitudinal spinelectric susceptibility is minimal. At these sweetspots, we measure an HahnEcho decay time $T2^{echo} = 100us while maintaining Rabi frequencies in the MHz range . This work opens new perspectives for quantum processing based on spinorbit qubits. 
Tuesday, March 15, 2022 4:00PM  4:12PM 
K39.00004: Electricdipole spin resonance for lightholes in germanium quantum well Patrick Del Vecchio, Oussama Moutanabbir Holes in Germanium (Ge) quantum wells (QW) have recently attracted a great deal of attention due to their numerous attractive properties for the realization of quantum processors. In contrast to electrons, holes are affected significantly by the large spinorbit coupling in Ge, enabling fast allelectrical spinmanipulation schemes such as electricdipole spin resonance (EDSR). A novel type of twodimensional hole gas consisting of lightholes can be achieved by applying a significant amount of tensile train (>1%) to the QW. A lighthole based quantum device also benefits of a more efficient photontospin interface. This work discusses the properties of lighthole spins in highly tensile strained Ge QWs, whose strain is caused by coherent growth onto highly relaxed germaniumtin buffer layers. A perturbative framework describing Rabiflopping of a light hole spin in a parabolic isotropic gatedefined quantum dot is derived from 8band k·p theory. A quantitative analysis of the Rabi frequency versus physical parameters shows that lightholes can be manipulated 2 to 3 orders of magnitude faster than heavyholes. The framework explicitly takes in account the spread of the envelope wavefunctions into the barriers and is suitable for any outofplane confining potential. 
Tuesday, March 15, 2022 4:12PM  4:24PM 
K39.00005: Anisotropy of hole spin qubits in a silicon fin fieldeffect transistor Simon Geyer, Leon Camenzind, Andreas Fuhrer, Richard J Warburton, Dominik M Zumbuhl, Andreas V Kuhlmann Hole spin qubits in silicon quantum dots have a great potential for scaling up quantum circuits, due to the small footprint of the devices and their industry compatibility. 
Tuesday, March 15, 2022 4:24PM  4:36PM 
K39.00006: Combining nMOS Charge Sensing with pMOS Silicon Hole Double Quantum Dots in a CMOS platform Ikkyeong Jin, Scott D Liles, Krittika Kumar, Matthew J Rendell, Christopher Escott, Fay E Hudson, Wee Han Lim, Andrew S Dzurak, Alex R Hamilton Silicon hole quantum dots are an interesting complement to conventional electron quantum dots as a way to realise scalable spin qubits. The strong spinorbit interaction in holes allows allelectric spin control [1]. Recent calculations also suggest it is possible to engineer a “sweet spot” for holes, where environmental decoherence is minimised, while simultaneously allowing rapid spin control [2]. However, the fabrication of ptype devices is not as developed as ntype. As such, disorder and device instability are challenges in ptype devices, and isolation of a single hole in a planar silicon quantum dot was demonstrated only recently [3]. 
Tuesday, March 15, 2022 4:36PM  4:48PM 
K39.00007: Quantum Coherence in Germanium Hole Spin Qubits William Iain L Lawrie, Nico W Hendrickx, Floor Van Riggelen, Maximilian Russ, David Linteau, Pericles Philippopoulos, Sander L de Snoo, Amir Sammak, Giordano Scappucci, William A Coish, Menno Veldhorst The ability to reliably store quantum information is an underpinning assumption for the operation of a quantum computer. This ability is compromised when qubits exchange energy with external systems in a process known as decoherence. In spin qubit systems, decoherence can be quantified by the time the transeverse component of a spin state takes to dephase (T2). For hole spin qubits in planar germanium (Ge/SiGe), pure dephasing times (T2*) have been limited to a few hundred nanoseconds. 
Tuesday, March 15, 2022 4:48PM  5:00PM 
K39.00008: Electrical control of the gtensor of the first holein a silicon MOS quantum dot Scott D Liles, Frederico Martins, Dmitry Miserev, Andrey A Kiselev, Ian Thorvaldson, Matthew J Rendell, Ikkyeong Jin, Fay E Hudson, Menno Veldhorst, Kohei M Itoh, Oleg P Sushkov, Thaddeus D Ladd, Andrew S Dzurak, Alex R Hamilton The spin state of a single hole in a semiconductor device provides a promising platform for a wide range of spin based quantum devices. A primary advantage of using holes, rather than electrons, is the intrinsically strong coupling of hole spins to electric fields. This strong spinelectric coupling allows rapid allelectrical control over the hole spin state, which is advantageous for many spin based devices, such as spin qubits [12]. However, due to the complexity of hole spin physics, gaps remain in our understanding of the mechanisms that enable electrical control of hole spins. 
Tuesday, March 15, 2022 5:00PM  5:12PM 
K39.00009: Towards holespin qubits in Si pMOSFETs within a planar CMOS foundry technology Filippo Troiani, Laura Bellentani, Andrea Secchi, Andrea Bertoni, Matteo Bina, Andrea Padovani, Luca Larcher, Shai Bonen, Sorin Voinigescu Hole spins in semiconductor quantum dots represent a viable route for the implementation of electrically controlled qubits. In particular, the qubit implementation based on Si pMOSFETs offers great potentialities in terms of integration with the control electronics and longterm scalability. 
Tuesday, March 15, 2022 5:12PM  5:24PM 
K39.00010: Allelectrical control of hole singlettriplet spin qubits at low leakage points Philipp M Mutter, Guido Burkard We study the effect of the spinorbit interaction on heavy holes confined in a double quantum dot in the presence of a magnetic field of arbitrary direction. Rich physics arise as the two hole states of different spin are not only coupled by the spinorbit interaction but additionally by the effect of sitedependent anisotropic g tensors. It is demonstrated that these effects may counteract in such a way as to cancel the coupling at certain detunings and tilting angles of the magnetic field. This feature may be used in singlettriplet qubits to avoid leakage errors and implement an electrical spinorbit switch, suggesting the possibility of tasktailored twoaxes control. Additionally, we investigate systems with a strong spinorbit interaction at weak magnetic fields. By exact diagonalization of the dominant Hamiltonian we find that the magnetic field may be chosen such that the qubit ground state is mixed only within the logical subspace for realistic system parameters, hence reducing leakage errors and providing reliable control over the qubit. 
Tuesday, March 15, 2022 5:24PM  5:36PM 
K39.00011: Electron and Hole Spin Qubits Variability in Si MOS Devices Biel Martinez Diaz, YannMichel Niquet Semiconductor spin qubits may show significant devicetodevice variability in the presence of spinorbit coupling mechanisms. Interface roughness, charge traps, layout or process inhomogeneities indeed shape the real space wave functions, hence the spin properties. It is, therefore, important to understand how reproducible the qubits can be in order to assess strategies to cope with this disorder. Here we model the variability of the Larmor/Rabi frequencies and spin lifetimes due to roughness and charge traps at the Si/SiO2 interface in metaloxidesemiconductor devices. We consider both electron qubits (with synthetic spinorbit coupling fields created by micromagnets) and hole qubits (with intrinsic spinorbit coupling). We highlight, in particular, the relations between the characteristic sizes of the disordered dots and their Larmor and Rabi frequencies. We show that the hole qubits are typically more sensitive to interface roughness than electron qubits due to the smaller hole confinement mass. Yet the main source of variability is charged traps, which can scatter the Rabi frequencies of both electron and hole qubits over one order of magnitude in realistic device layouts. We analyze the implications for the design of spin qubits and for the choice of materials. 
Tuesday, March 15, 2022 5:36PM  5:48PM 
K39.00012: Hole spin qubits in Si and Ge quantum dots: Ultrafastgates and noise resilient qubits Stefano Bosco, Daniel Loss Hole spin qubits in Si and Ge quantum dots are frontrunner platforms for scalable quantum computers. In these systems, the spinorbit interactions permit efficient and ultrafast allelectric qubit control, but, at the same time, enhance the susceptibility of the qubit to charge noise. We show that in planar Ge/SiGe heterostructures and in Si fin fieldeffect transistors (FinFETs), these interactions can be fully tuned by the design of the quantum dot and by external electric fields [1], enabling sweet spots where the charge noise can be completely removed [2]. Remarkably, in Si FInFETs, also the noise caused by hyperfine interactions with nuclear spins another leading source of decoherence in spin qubits can be suppressed at these sweet spots [3], greatly enhancing the coherence of these qubits, and reducing the need for expensive isotopically purified materials. 
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