Abstract
The strong spin-orbit coupling in hole spin qubits enables fast and electrically tunable gates, but at the same time enhances the susceptibility of the qubit to charge noise. Suppressing this noise is a significant challenge in semiconductor quantum computing. Here, we show theoretically that hole Si FinFETs are not only very compatible with modern CMOS technology, but they present operational sweet spots where the charge noise is completely removed. The presence of these sweet spots is a result of the interplay between the anisotropy of the material and the triangular shape of the FinFET cross-section, and it does not require an extreme fine-tuning of the electrostatics of the device. We present how the sweet spots appear in FinFETs grown along different crystallographic axes and we study in detail how the behaviour of these devices change when the cross-section area and aspect ratio are varied. We identify designs that maximize the qubit performance and could pave the way towards a scalable spin-based quantum computer.
Highlights
Strong spin-orbit coupling [1] is a desirable ingredient to build a scalable spin-based quantum computer [2,3], enabling fast and fully electrical manipulations of quantum bits [4,5,6]
This model provides an accurate description of SOI fin field-effect transistors (FinFETs), but it is questionable in bulk Si FinFETs, where there is no sharp interface at the bottom of the fin and the wavefunction can leak into the bulk
We present ways of suppressing charge noise in hole Si FinFET qubits
Summary
Strong spin-orbit coupling [1] is a desirable ingredient to build a scalable spin-based quantum computer [2,3], enabling fast and fully electrical manipulations of quantum bits [4,5,6]. To remove charge noise in these systems, one needs the ability to ondemand fully switch on and off the spin-orbit interactions depending on whether the qubit is operational or idle We find that such a spin-orbit switch naturally occurs in p-doped silicon fin field-effect transistors (FinFETs) [40,41,42], making these devices ideal candidates to reliably store quantum information. A crucial feature of the Si FinFETs studied here is their nearly triangular cross section, which results in sweet spots where the spin-orbit coupling can be switched off at finite values of the electric field, removing the charge noise. We show that holes confined in triangular wires present a large spin-orbit coupling even without electric fields and, depending on the design of the fin, an external gate potential can suppress this intrinsic coupling. By including in our analysis the fluctuations of the g factor as a function of the electric field, a charge noise mechanism that is not directly related to the effective spin-orbit coupling of the wire, the exact position of the sweet spot is slightly shifted, but the charge noise can still be exactly canceled, resulting in a system fully resilient against small charge fluctuations
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