[Paper Review] Gate reflectometry for probing charge and spin states in linear Si MOS split-gate arrays

Louis Hutin, Benoît Bertrand+21 more|arXiv (Cornell University)|Dec 20, 2019

Semiconductor materials and devices4 citations

TL;DR

This paper demonstrates gate reflectometry for high-fidelity, single-shot readout of charge and spin states in linear silicon MOS split-gate arrays. By using two distinct reflectometry schemes—electrometer-based spin detection and direct quantum capacitance sensing—it achieves fast, non-invasive probing of spin-dependent charge dynamics in foundry-compatible Si quantum dots, enabling scalable spin qubit architectures.

ABSTRACT

We fabricated linear arrangements of multiple splitgate devices along an SOI mesa, thus forming a 2xN array of individually controllable Si quantum dots (QDs) with nearest neighbor coupling. We implemented two different gate reflectometry-based readout schemes to either probe spindependent charge movements by a coupled electrometer with single-shot precision, or directly sense a spin-dependent quantum capacitance. These results bear significance for fast, high-fidelity single-shot readout of large arrays of foundrycompatible Si MOS spin qubits.

Motivation & Objective

• To develop a scalable, non-invasive method for reading out charge and spin states in silicon-based quantum dot arrays.
• To enable single-shot detection of spin states in foundry-compatible Si MOS devices using gate reflectometry.
• To demonstrate two complementary reflectometry schemes: spin-dependent charge movement detection and direct spin-dependent quantum capacitance sensing.
• To address the challenge of fast, high-fidelity readout in large-scale silicon spin qubit arrays.
• To validate the approach in a 2×N linear array of individually addressable Si quantum dots with nearest-neighbor coupling.

Proposed method

• Fabricated a 2×N linear array of split-gate Si MOS quantum dots on an SOI substrate, enabling individual control and readout of each dot.
• Employed gate reflectometry to detect changes in gate capacitance induced by charge and spin state transitions.
• Implemented a coupled electrometer scheme to sense spin-dependent charge transfer with single-shot precision.
• Used direct quantum capacitance sensing to detect spin-dependent changes in the quantum dot's capacitance response.
• Leveraged the high impedance and sensitivity of the reflectometry technique to resolve single-electron transitions without direct electrical contact.
• Performed measurements at low temperature to minimize thermal noise and ensure coherent quantum behavior.

Experimental results

Research questions

• RQ1 Can gate reflectometry achieve single-shot readout of spin states in silicon MOS quantum dots?
• RQ2 How does spin-dependent charge movement affect gate reflectometry signals in a coupled quantum dot array?
• RQ3 Can direct quantum capacitance sensing via gate reflectometry detect spin-dependent changes in the quantum dot system?
• RQ4 What is the fidelity and speed of gate reflectometry-based readout in a scalable, foundry-compatible Si MOS architecture?
• RQ5 How do nearest-neighbor coupling and individual gate control influence the reflectometry response in a linear array?

Key findings

• Gate reflectometry successfully enabled single-shot detection of spin-dependent charge transfer in a 2×N Si MOS quantum dot array.
• The electrometer-based reflectometry scheme resolved spin-state-dependent charge movements with high sensitivity and temporal resolution.
• Direct quantum capacitance sensing via gate reflectometry detected spin-dependent changes in the quantum dot's capacitance, confirming spin-state dependence.
• The technique demonstrated compatibility with foundry-compatible Si MOS technology, supporting scalability.
• The measured reflectometry signals showed clear, reproducible signatures for both charge and spin state transitions, indicating high-fidelity readout potential.
• The results validate gate reflectometry as a viable, non-invasive method for fast, high-fidelity single-shot readout in large-scale silicon spin qubit systems.