Quantum Computing with Acceptor Spins in Silicon

TL;DR

This paper demonstrates that acceptor spins in silicon can serve as highly controllable qubits for quantum computing, utilizing interface-induced spin-orbit interactions for initialization, manipulation, and entanglement with high fidelity.

Contribution

It provides analytical and numerical evidence that heavy-hole spin qubits in acceptors can be reliably controlled electrically, highlighting their potential for scalable silicon-based quantum computers.

Findings

Heavy-hole spin qubits can be initialized, rotated, and entangled electrically.

Interface-induced spin-orbit interactions enable high-fidelity control.

Sweet spots in dephasing time T2* are linked to EDSR strength maxima.

Abstract

The states of a boron acceptor near a Si/SiO2 interface, which bind two low-energy Kramers pairs, have exceptional properties for encoding quantum information and, with the aid of strain, both heavy hole and light hole-based spin qubits can be designed. Whereas a light-hole spin qubit was introduced recently [Phys. Rev. Lett. 116, 246801 (2016)], here we present analytical and numerical results proving that a heavy-hole spin qubit can be reliably initialised, rotated and entangled by electrical means alone. This is due to strong Rashba-like spin-orbit interaction terms enabled by the interface inversion asymmetry. Single qubit rotations rely on electric-dipole spin resonance (EDSR), which is strongly enhanced by interface-induced spin-orbit terms. Entanglement can be accomplished by Coulomb exchange, coupling to a resonator, or spin-orbit induced dipole-dipole interactions. By analysing the qubit sensitivity to charge noise, we demonstrate that interface-induced spin-orbit terms are responsible for sweet spots in the dephasing time T2* as a function of the top gate electric field, which are close to maxima in the EDSR strength, where the EDSR gate has high fidelity. We show that both qubits can be described using the same starting Hamiltonian, and by comparing their properties we show that the complex interplay of bulk and interface-induced spin-orbit terms allows a high degree of electrical control and makes acceptors potential candidates for scalable quantum computation in Si.