# Tunable coupling and isolation of single electrons in silicon metal-oxide-semiconductor quantum dots

## TL;DR

This paper demonstrates the ability to tune the tunnel coupling between single electrons in silicon MOS quantum dots over a wide frequency range, enabling improved control for quantum computing.

## Contribution

It introduces a method to achieve and control tunable tunnel coupling in silicon quantum dots, a long-standing challenge in the field.

## Key findings

- Tunable coupling up to 13 GHz achieved.
- Tunable tunnel rates below 1 Hz demonstrated.
- Charge sensing effectively discriminates charge states.

## Abstract

Extremely long coherence times, excellent single-qubit gate fidelities and two-qubit logic have been demonstrated with silicon metal-oxide-semiconductor spin qubits, making it one of the leading platforms for quantum information processing. Despite this, a long-standing challenge in this system has been the demonstration of tunable tunnel coupling between single electrons. Here we overcome this hurdle with gate-defined quantum dots and show couplings that can be tuned on and off for quantum operations. We use charge sensing to discriminate between the (2,0) and (1,1) charge states of a double quantum dot and show excellent charge sensitivity. We demonstrate tunable coupling up to 13 GHz, obtained by fitting charge polarization lines, and tunable tunnel rates down to below 1 Hz, deduced from the random telegraph signal. The demonstration of tunable coupling between single electrons in a silicon metal-oxide-semiconductor device provides significant scope for high-fidelity two-qubit logic toward quantum information processing with standard manufacturing.