Robust multi-qubit quantum network node with integrated error detection

TL;DR

This paper demonstrates an integrated silicon-vacancy based quantum network node with long-lived nuclear spin memory and error detection capabilities, advancing scalable quantum communication technologies.

Contribution

It introduces a two-qubit quantum network node with integrated error detection using SiV centers in diamond nanophotonics, featuring long coherence times and elevated temperature operation.

Findings

Nuclear spin memory exceeds two seconds.

Electron-photon entangling gates operate up to 1.5 K.

Error detection implemented via electron spin as a flag qubit.

Abstract

Long-distance quantum communication and networking require quantum memory nodes with efficient optical interfaces and long memory times. We report the realization of an integrated two-qubit network node based on silicon-vacancy centers (SiVs) in diamond nanophotonic cavities. Our qubit register consists of the SiV electron spin acting as a communication qubit and the strongly coupled 29Si nuclear spin acting as a memory qubit with a quantum memory time exceeding two seconds. By using a highly strained SiV with suppressed electron spin-phonon interactions, we realize electron-photon entangling gates at elevated temperatures up to 1.5 K and nucleus-photon entangling gates up to 4.3 K. Finally, we demonstrate efficient error detection in nuclear spin-photon gates by using the electron spin as a flag qubit, making this platform a promising candidate for scalable quantum repeaters.