scholarly journals Optimal operation points for ultrafast, highly coherent Ge hole spin-orbit qubits

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Zhanning Wang ◽  
Elizabeth Marcellina ◽  
Alex. R. Hamilton ◽  
James H. Cullen ◽  
Sven Rogge ◽  
...  
Keyword(s):  
Electric Field ◽  
Optimal Operation ◽  
Group Iv ◽  
Spin Orbit ◽  
Spin Qubits ◽  
Resonance Strength ◽  
Spin Qubit ◽  
Field Noise ◽  
Electrical Spin ◽  
Spin Orbit Interactions

AbstractStrong spin-orbit interactions make hole quantum dots central to the quest for electrical spin qubit manipulation enabling fast, low-power, scalable quantum computation. Yet it is important to establish to what extent spin-orbit coupling exposes qubits to electrical noise, facilitating decoherence. Here, taking Ge as an example, we show that group IV gate-defined hole spin qubits generically exhibit optimal operation points, defined by the top gate electric field, at which they are both fast and long-lived: the dephasing rate vanishes to first order in the electric field noise along with all directions in space, the electron dipole spin resonance strength is maximized, while relaxation is drastically reduced at small magnetic fields. The existence of optimal operation points is traced to group IV crystal symmetry and properties of the Rashba spin-orbit interaction unique to spin-3/2 systems. Our results overturn the conventional wisdom that fast operation implies reduced lifetimes and suggest group IV hole spin qubits as ideal platforms for ultra-fast, highly coherent scalable quantum computing.

scholarly journals Electric field control of spin-orbit torque switching in a spin-orbit ferromagnet single layer

2020 ◽  
Author(s):  
Miao Jiang ◽  
Hirokatsu Asahara ◽  
Shinobu Ohya ◽  
Masaaki Tanaka
Keyword(s):  
Electric Field ◽  
Single Layer ◽  
Field Application ◽  
Spin Orbit ◽  
Interface Quality ◽  
Field Control ◽  
Spin Orbit Interactions ◽  
Switching Efficiency ◽  
A Current ◽  
Strong Spin

Abstract To achieve a desirable magnitude of spin-orbit torque (SOT) switching and realise multifunctional spin logic and memory devices utilising SOT, controlling the SOT manipulation is vitally important. In conventional SOT bilayer systems, researchers have tried to control the switching behaviour via interfacial oxidisation; however, the switching efficiency is limited by the interface quality. A current-induced effective magnetic field in a single layer of a ferromagnet with strong spin-orbit interactions, the so-called spin-orbit ferromagnet, can be utilised to induce SOT. In spin-orbit ferromagnet systems, electric field application has potential for manipulating the spin-orbit interactions via carrier concentration modulation. In this work, we demonstrate that SOT switching can be successfully controlled via an external electric field using a (Ga,Mn)As single layer. By applying a gate voltage, the switching current density can be solidly and reversibly manipulated with a large ratio of 14.5%, which is ascribed to the successful modulation of the interfacial electric field. Our findings help further the understanding of the magnetisation switching mechanism and advance the development of gate-controlled SOT devices.

scholarly journals Ultrafast coherent control of a hole spin qubit in a germanium quantum dot

2022 ◽  
Vol 13 (1) ◽  
Author(s):  
Ke Wang ◽  
Gang Xu ◽  
Fei Gao ◽  
He Liu ◽  
Rong-Long Ma ◽  
...  
Keyword(s):  
Quantum Dot ◽  
Coherent Control ◽  
Coherence Time ◽  
Double Quantum ◽  
Spin Orbit ◽  
Spin Qubits ◽  
Single Spin ◽  
Operation Speed ◽  
Spin Qubit ◽  
Core Measures

AbstractOperation speed and coherence time are two core measures for the viability of a qubit. Strong spin-orbit interaction (SOI) and relatively weak hyperfine interaction make holes in germanium (Ge) intriguing candidates for spin qubits with rapid, all-electrical coherent control. Here we report ultrafast single-spin manipulation in a hole-based double quantum dot in a germanium hut wire (GHW). Mediated by the strong SOI, a Rabi frequency exceeding 540 MHz is observed at a magnetic field of 100 mT, setting a record for ultrafast spin qubit control in semiconductor systems. We demonstrate that the strong SOI of heavy holes (HHs) in our GHW, characterized by a very short spin-orbit length of 1.5 nm, enables the rapid gate operations we accomplish. Our results demonstrate the potential of ultrafast coherent control of hole spin qubits to meet the requirement of DiVincenzo’s criteria for a scalable quantum information processor.

Spin generation and manipulation based on spin-orbit interaction in semiconductors

2017 ◽  
Author(s):  
J. Nitta
Keyword(s):  
Magnetic Field ◽  
Orbit Interaction ◽  
Degree Of Freedom ◽  
Effective Magnetic Field ◽  
Spin Orbit ◽  
Spin Orbit Interaction ◽  
Spin Degree ◽  
Dimensional Electron Gas ◽  
Spin Orbit Interactions ◽  
Electrical Generation

This chapter focuses on the electron spin degree of freedom in semiconductor spintronics. In particular, the electrostatic control of the spin degree of freedom is an advantageous technology over metal-based spintronics. Spin–orbit interaction (SOI), which gives rise to an effective magnetic field. The essence of SOI is that the moving electrons in an electric field feel an effective magnetic field even without any external magnetic field. Rashba spin–orbit interaction is important since the strength is controlled by the gate voltage on top of the semiconductor’s two-dimensional electron gas. By utilizing the effective magnetic field induced by the SOI, spin generation and manipulation are possible by electrostatic ways. The origin of spin-orbit interactions in semiconductors and the electrical generation and manipulation of spins by electrical means are discussed. Long spin coherence is achieved by special spin helix state where both strengths of Rashba and Dresselhaus SOI are equal.

scholarly journals Intersystem crossing processes in the 2CzPN emitter: a DFT/MRCI study including vibrational spin–orbit interactions

2021 ◽  
Vol 23 (5) ◽  
pp. 3668-3678
Author(s):  
Angela Rodriguez-Serrano ◽  
Fabian Dinkelbach ◽  
Christel M. Marian
Keyword(s):  
Quantum Chemical Calculations ◽  
Quantum Chemical ◽  
Intersystem Crossing ◽  
Spin Orbit ◽  
Spin Orbit Interactions

Multireference quantum chemical calculations were performed in order to investigate the (reverse) intersystem crossing ((R)ISC) mechanisms of 4,5-di(9H-carbazol-9-yl)-phthalonitrile (2CzPN).

scholarly journals Fundamental limits of electron and nuclear spin qubit lifetimes in an isolated self-assembled quantum dot

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
George Gillard ◽  
Ian M. Griffiths ◽  
Gautham Ragunathan ◽  
Ata Ulhaq ◽  
Callum McEwan ◽  
...  
Keyword(s):  
Quantum Dot ◽  
Spin Relaxation ◽  
Nuclear Spin ◽  
Operating Conditions ◽  
External Control ◽  
Spin Qubits ◽  
Fundamental Limits ◽  
Trade Offs ◽  
Wide Range ◽  
Spin Qubit

AbstractCombining external control with long spin lifetime and coherence is a key challenge for solid state spin qubits. Tunnel coupling with electron Fermi reservoir provides robust charge state control in semiconductor quantum dots, but results in undesired relaxation of electron and nuclear spins through mechanisms that lack complete understanding. Here, we unravel the contributions of tunnelling-assisted and phonon-assisted spin relaxation mechanisms by systematically adjusting the tunnelling coupling in a wide range, including the limit of an isolated quantum dot. These experiments reveal fundamental limits and trade-offs of quantum dot spin dynamics: while reduced tunnelling can be used to achieve electron spin qubit lifetimes exceeding 1 s, the optical spin initialisation fidelity is reduced below 80%, limited by Auger recombination. Comprehensive understanding of electron-nuclear spin relaxation attained here provides a roadmap for design of the optimal operating conditions in quantum dot spin qubits.

scholarly journals Effect of Spin-Orbit Interactions on the 0.7 Anomaly in Quantum Point Contacts

2014 ◽  
Vol 113 (26) ◽  
Author(s):  
Olga Goulko ◽  
Florian Bauer ◽  
Jan Heyder ◽  
Jan von Delft
Keyword(s):  
Quantum Point Contacts ◽  
Spin Orbit ◽  
Point Contacts ◽  
Quantum Point ◽  
0.7 Anomaly ◽  
Spin Orbit Interactions

scholarly journals Layer- and gate-tunable spin-orbit coupling in a high-mobility few-layer semiconductor

2021 ◽  
Vol 7 (5) ◽  
pp. eabe2892
Author(s):  
Dmitry Shcherbakov ◽  
Petr Stepanov ◽  
Shahriar Memaran ◽  
Yaxian Wang ◽  
Yan Xin ◽  
...  
Keyword(s):  
Electric Field ◽  
High Mobility ◽  
Orbit Coupling ◽  
Spin Splitting ◽  
Spin Orbit Coupling ◽  
Spin Orbit ◽  
Quantum Oscillations ◽  
Out Of Plane ◽  
Order Of Magnitude ◽  
Spin Degeneracy

Spin-orbit coupling (SOC) is a relativistic effect, where an electron moving in an electric field experiences an effective magnetic field in its rest frame. In crystals without inversion symmetry, it lifts the spin degeneracy and leads to many magnetic, spintronic, and topological phenomena and applications. In bulk materials, SOC strength is a constant. Here, we demonstrate SOC and intrinsic spin splitting in atomically thin InSe, which can be modified over a broad range. From quantum oscillations, we establish that the SOC parameter α is thickness dependent; it can be continuously modulated by an out-of-plane electric field, achieving intrinsic spin splitting tunable between 0 and 20 meV. Unexpectedly, α could be enhanced by an order of magnitude in some devices, suggesting that SOC can be further manipulated. Our work highlights the extraordinary tunability of SOC in 2D materials, which can be harnessed for in operando spintronic and topological devices and applications.

scholarly journals Electric-Field Control of Spin–Orbit Torques in WS2/Permalloy Bilayers

2018 ◽  
Vol 10 (3) ◽  
pp. 2843-2849 ◽  
Author(s):  
Weiming Lv ◽  
Zhiyan Jia ◽  
Bochong Wang ◽  
Yuan Lu ◽  
Xin Luo ◽  
...  
Keyword(s):  
Electric Field ◽  
Spin Orbit ◽  
Field Control
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