# Phase-tuned entangled state generation between distant spin qubits

## TL;DR

This paper demonstrates a method for generating entanglement between distant semiconductor quantum dot spin qubits using optical techniques, achieving high fidelity and a record entanglement rate, advancing quantum network capabilities.

## Contribution

It introduces a novel protocol for optically entangling distant spin qubits via spin-photon entanglement and quantum erasure, with stabilized phase control.

## Key findings

- Achieved 61.6% Bell-state fidelity for entangled qubits.
- Recorded a high entanglement generation rate of 7.3 kHz.
- Demonstrated interferometrically stabilized and tunable phase control.

## Abstract

Quantum entanglement between distant qubits is an important feature of quantum networks. Distribution of entanglement over long distances can be enabled through coherently interfacing qubit pairs via photonic channels. Here, we report the realization of optically generated quantum entanglement between electron spin qubits confined in two distant semiconductor quantum dots. The protocol relies on spin-photon entanglement in the trionic $\Lambda$-system and quantum erasure of the Raman-photon path. The measurement of a single Raman photon is used to project the spin qubits into a joint quantum state with an interferometrically stabilized and tunable relative phase. We report an average Bell-state fidelity for $|\psi^{(+)}\rangle$ and $|\psi^{(-)}\rangle$ states of $61.6\pm2.3\%$ and a record-high entanglement generation rate of 7.3 kHz between distant qubits.