Characterization and Suppression of Low-frequency Noise in Si/SiGe Quantum Point Contacts and Quantum Dots

TL;DR

This study investigates how a global top gate influences low-frequency charge noise in Si/SiGe quantum point contacts and dots, demonstrating noise suppression and charge stability improvements crucial for quantum computing applications.

Contribution

It introduces a top-gating technique to suppress low-frequency noise and stabilize charge states in Si/SiGe quantum devices, advancing quantum dot control.

Findings

Top gate voltage reduces charge noise in QPCs and QDs.

Lowering top gate voltage suppresses Lorentzian 1/f2 noise.

Enhanced charge stability down to zero electrons in double QDs.

Abstract

We report on the effects of a global top gate on low-frequency noise in Schottky gate-defined quantum point contacts (QPCs) and quantum dots (QDs) in a modulation-doped Si/SiGe heterostructure. For a relatively large top gate voltage, the QPC current shows frequent switching with 1/f2 Lorentzian type charge noise. As the top gate voltage is decreased, the QPC pinch-off voltage becomes less negative, and the 1/f2 noise becomes rapidly suppressed in a homogeneous background 1/f noise. We apply this top-gating technique to double QDs to stabilize the charge state for the electron number down to zero.