Swap Test with Quantum-Dot Charge Qubits

TL;DR

This paper proposes implementing the Swap Test using charge qubits in double quantum dots, enabling fast, efficient fidelity estimation crucial for quantum machine learning applications.

Contribution

It introduces a practical method for executing the Swap Test with quantum-dot charge qubits using a natural controlled three-qubit gate.

Findings

Circuit depth of six layers

Gate time estimated below 3 ns

Compatible with quantum dot coherence times

Abstract

We propose the implementation of the Swap Test using a charge qubit in a double quantum dot. The Swap Test is a fundamental quantum subroutine in quantum machine learning and other applications for estimating the fidelity of two unknown quantum states by measuring an auxiliary qubit. Our proposal uses a controlled three-qubit gate which is natural to quantum-dot charge qubits. It allows us to implement a Swap Test with a circuit depth of six layers, and an estimated gate time of less than 3 ns, that is below the coherence time of double quantum dots. This work paves the way for enhancing the toolbox of quantum machine learning developments in semiconductor qubits.