# The exchange-only singlet-only spin qubit

## TL;DR

This paper introduces a scalable, exchange-only singlet-only spin qubit in quantum dots that is highly resistant to nuclear spin-induced magnetic noise, significantly enhancing coherence times.

## Contribution

It presents a novel implementation of a singlet-only spin qubit that is inherently insensitive to nuclear spin fluctuations, improving qubit coherence without complex shielding.

## Key findings

- Dephasing time T2* improved by several orders of magnitude.
- Qubit can be initialized, manipulated, and read out electrically.
- Intrinsic insensitivity to nuclear magnetic field fluctuations.

## Abstract

We propose a feasible and scalable quantum-dot-based implementation of a singlet-only spin qubit which is to leading order intrinsically insensitive to random effective magnetic fields set up by fluctuating nuclear spins in the host semiconductor. Our proposal thus removes an important obstacle for further improvement of spin qubits hosted in high-quality III-V semiconductors such as GaAs. We show how the resulting qubit could be initialized, manipulated, and read out by electrical means only, in a way very similar to a triple-dot exchange-only spin qubit. Due to the intrinsic elimination of the effective nuclear fields from the qubit Hamiltonian, we find an improvement of the dephasing time $T_2^*$ of several orders of magnitude as compared to similar existing spin qubits.