Hybrid entanglement and error correction in a scalable quantum network node

TL;DR

This paper demonstrates a hybrid quantum node based on diamond color centers that integrates multiple qubit types, enabling complex control, entanglement, and active error correction, advancing scalable quantum networks.

Contribution

It introduces a hybrid quantum node with multi-qubit control, entanglement, and real-time error correction, crucial for scalable quantum network development.

Findings

Successfully entangled electron, nuclear, and photonic qubits across different regimes.

Implemented three-qubit error correction with repeated syndrome readout and feedback.

Achieved active error correction over twelve rounds, improving fidelity.

Abstract

Recent breakthroughs have ushered the quantum network into a new era, where quantum information can be stored, transferred, and processed across multiple nodes on a metropolitan scale. A key challenge in this new era is enhancing the capabilities of individual nodes, providing precise and robust control over multiple qubits and advanced functionality for scalable quantum networks. Here, we report on precise and complex control in a hybrid quantum node based on a diamond color center. We demonstrate hybrid coherent control by entangling three types of qubits: an electron spin as an interface qubit, a nuclear spin with long memory time, and a flying photonic qubit, with their qubit frequencies spanning three distinct regimes from the optical domain to the rf domain. By incorporating two additional memory qubits, we encode three memory qubits into a logical state using the three-qubit repetition code and entangle this logical qubit with a photonic qubit. Leveraging hybrid qubits and precise control, we repeatedly read out the error syndromes of memory qubits through the electron spin, serving as an auxiliary qubit, then apply a real-time feedback operation to correct bit-flip errors. We execute and verify active error correction for up to twelve rounds and demonstrate the improvement over the uncorrected counterpart. Our results demonstrate the feasibility of several key functionalities for next-generation quantum repeaters, paving the way towards full-fledged metropolitan-scale quantum networks for a wide range of practical applications.