Quantum-network nodes with real-time noise mitigation using spectator qubits

TL;DR

This paper presents a method using spectator qubits with real-time decision making to mitigate dephasing in quantum network nodes, demonstrated with NV centers in diamond.

Contribution

The authors introduce a novel protocol employing spectator qubits and real-time feedback to enhance quantum memory fidelity during entanglement generation.

Findings

Improved memory fidelity using spectator qubits.

Demonstrated protocol with NV centers in diamond.

Minimal overhead for noise mitigation.

Abstract

Quantum networks might enable quantum communication and distributed quantum computation. Solid-state defects are promising platforms for such networks, because they provide an optical interface for remote entanglement distribution and a nuclear-spin register to store and process quantum information. A key challenge towards larger networks is to improve the storage of previously generated entangled states during new entanglement generation. Here, we introduce a method that uses `spectator' qubits combined with real-time decision making and feedforward to mitigate dephasing of stored quantum states during remote entanglement sequences. We implement the protocol using a single NV center in diamond and demonstrate improved memory fidelity. Our results show that spectator qubits can improve quantum network memory using minimal overhead and naturally present resources, making them a promising addition for near-term testbeds for quantum networks.