Dispersively detected Pauli Spin-Blockade in a Silicon Nanowire Field-Effect Transistor

TL;DR

This paper demonstrates dispersive readout of spin states in a silicon nanowire quantum dot device, revealing Pauli spin-blockade and valley-orbit splitting, advancing silicon-based quantum computing prospects.

Contribution

It introduces a gate-based RF reflectometry technique for spin readout in silicon nanowire transistors, eliminating external sensors and enabling compact qubit architectures.

Findings

Observation of Pauli spin-blockade in high-frequency response.

Detection of intra-dot valley-orbit splitting of 145 μeV.

Potential for silicon nanowire devices as singlet-triplet qubits.

Abstract

We report the dispersive readout of the spin state of a double quantum dot formed at the corner states of a silicon nanowire field-effect transistor. Two face-to-face top-gate electrodes allow us to independently tune the charge occupation of the quantum dot system down to the few-electron limit. We measure the charge stability of the double quantum dot in DC transport as well as dispersively via in-situ gate-based radio frequency reflectometry, where one top-gate electrode is connected to a resonator. The latter removes the need for external charge sensors in quantum computing architectures and provides a compact way to readout the dispersive shift caused by changes in the quantum capacitance during interdot charge transitions. Here, we observe Pauli spin-blockade in the high-frequency response of the circuit at finite magnetic fields between singlet and triplet states. The blockade is lifted at higher magnetic fields when intra-dot triplet states become the ground state configuration. A lineshape analysis of the dispersive phase shift reveals furthermore an intradot valley-orbit splitting $\Delta_{vo}$ of 145 $\mu$eV. Our results open up the possibility to operate compact CMOS technology as a singlet-triplet qubit and make split-gate silicon nanowire architectures an ideal candidate for the study of spin dynamics.