A single hole spin with enhanced coherence in natural silicon

Abstract

Semiconductor spin qubits based on spin–orbit states are responsive to electric field excitations, allowing for practical, fast and potentially scalable qubit control. Spin electric susceptibility, however, renders these qubits generally vulnerable to electrical noise, which limits their coherence time. Here we report on a spin–orbit qubit consisting of a single hole electrostatically confined in a natural silicon metal-oxide-semiconductor device. By varying the magnetic field orientation, we reveal the existence of operation sweet spots where the impact of charge noise is minimized while preserving an efficient electric-dipole spin control. We correspondingly observe an extension of the Hahn-echo coherence time up to 88 μs, exceeding by an order of magnitude existing values reported for hole spin qubits, and approaching the state-of-the-art for electron spin qubits with synthetic spin–orbit coupling in isotopically purified silicon. Our finding enhances the prospects of silicon-based hole spin qubits for scalable quantum information processing.

Compilation and scaling strategies for a silicon quantum processor with sparse two-dimensional connectivity

“…In the case of hole spin qubits, the larger spin-orbit coupling when compared to electron spins allows for all-electrical control via individual microwave voltage signals applied directly to the relevant QD gates 72,73 . The spin coherence is relatively lower, with T Ã 2 values of up to 7.1 μs reported 74 , but the faster Rabi frequencies, of up to 150 MHz, have enabled X and Y rotation with fidelity in excess of 99% 73,75 .…”

Recent advances in hole-spin qubits

“…In Ge/Si core/shell nanowires, the g-factor can be strongly quenched along the direction of the nanowire [57,58]. A recent detailed analysis of g-factors in a silicon nanowire device, together with their dependence on various gate potentials, can be found in [59]. A thorough characterization of the gate dependence and anisotropy is important to determine suitable sweet spots, at which the hole-spin qubit is less sensitive to charge noise [41,[59][60][61].…”

“…(electrons) (holes) reason, hole-spin dephasing is often related to the spectral properties of the classical charge noise (see, for example [20,59,68]). We also note that the EDSR strength is linear in the spin-orbit coupling, while the relaxation and dephasing rates are quadratic.…”

“…In all of them, the quantum dots are formed by charge accumulation at the Si/oxide interface, induced by top metallic gates. Panel (a) represents a planar geometry [185][186][187], while in panel (b) the quantum dots are based on a nanowire field-effect transistor (FET) [22,59,[188][189][190][191][192]. In the FinFET geometry of panel (c), similar to a nanowire, holes are confined at the top of a Si extrusion with a triangular cross-section [81,184,193].…”

“…The effective g-tensor in these Si quantum dots is anisotropic, although not as strongly as for other types of hole-spin qubits, and can be significantly affected by small variations of the gate voltages [59,187,190,191]. For example, in a quantum dot based on a nanowire FET, it is possible to modulate the g-factor in the in-plane direction perpendicular to the channel from g = 1.85 to 2.6 [190].…”