Universal set of quantum gates for double-dot spin qubits with fixed interdot coupling

TL;DR

This paper introduces a universal set of quantum gates for double-dot spin qubits that operate with fixed interdot coupling, using electrical bias control, simplifying quantum gate implementation.

Contribution

It presents a novel approach to implement universal quantum gates for singlet-triplet qubits without requiring dynamic control of tunnel coupling.

Findings

Effective qubit rotation angles are calculated as a function of electric bias.

Explicit sequences for single-qubit rotations are provided.

A CNOT gate sequence is demonstrated, enabling universal quantum computation.

Abstract

We propose a set of universal gate operations for the singlet-triplet qubit realized by two electron spins in a double quantum dot, in the presence of a fixed inhomogeneous magnetic field. All gate operations are achieved by switching the potential offset between the two dots with an electrical bias, and do not require time-dependent control of the tunnel coupling between the dots. We analyze the two-electron dynamics and calculate the effective qubit rotation angle as a function of the applied electric bias. We present explicit gate sequences for single-qubit rotations about two orthogonal axes, and a CNOT gate sequence, completing the universal gate set.