Robust quantum-network memory using decoherence-protected subspaces of nuclear spins

TL;DR

This paper demonstrates a quantum network node using NV centers with nuclear spins, achieving decoherence-protected quantum memory that maintains coherence over many entangling attempts, advancing quantum communication technology.

Contribution

It introduces a method to encode quantum information into decoherence-protected subspaces of nuclear spins, significantly extending quantum coherence in NV center-based network nodes.

Findings

Quantum coherence maintained over 1000 entangling repetitions.

Individual control and readout of five nuclear spin qubits.

Storage fidelity limited by electronic spin dephasing.

Abstract

The realization of a network of quantum registers is an outstanding challenge in quantum science and technology. We experimentally investigate a network node that consists of a single nitrogen-vacancy (NV) center electronic spin hyperfine-coupled to nearby nuclear spins. We demonstrate individual control and readout of five nuclear spin qubits within one node. We then characterize the storage of quantum superpositions in individual nuclear spins under repeated application of a probabilistic optical inter-node entangling protocol. We find that the storage fidelity is limited by dephasing during the electronic spin reset after failed attempts. By encoding quantum states into a decoherence-protected subspace of two nuclear spins we show that quantum coherence can be maintained for over 1000 repetitions of the remote entangling protocol. These results and insights pave the way towards remote entanglement purification and the realisation of a quantum repeater using NV center quantum network nodes.