Researchers attain coherent control of a hybrid quantum network node

Quantum technologies, which operate leveraging quantum mechanical phenomena, have the potential to outperform their classical counterparts in some optimization and computational tasks. These technologies include so-called quantum networks, systems designed to transmit information between interconnected nodes and process it, using quantum phenomena such as entanglement and superposition.

Quantum networks could eventually contribute to the advancement of communications, sensing and computing. Before this can happen, however, existing systems will need to be improved and perfected, to ensure that they can transfer and process data both reliably and efficiently, minimizing errors.

Researchers at Tsinghua University, Hefei National Laboratory and the Beijing Academy of Quantum Information Sciences recently demonstrated the coherent control of a hybrid and scalable quantum network node. Their demonstration, outlined in Nature Physics, was realized by combining solutions and techniques that they developed as part of their earlier work.

“Our long-term goal is to establish a scalable quantum network using diamond color centers (here nitrogen-vacancy centers),” Panyu Hou, co-author of the paper, told Phys.org.

“While our team and other research groups in the field have developed various critical techniques, including spin-photon entanglement generation, quantum control of hybrid qubits, and quantum error correction, these ingredients have not been integrated in a single quantum system. Our recent paper pursues this goal.”

Building on their earlier studies, Hou and his colleagues successfully demonstrated the coherent control of three different types of qubits, each of which contributes to the overall activity of their quantum network. In addition, the researchers implemented bit-flip error correction techniques on their network and were able to detect the errors of logical qubits entangled with a single photon.

The successful implementation of these techniques is of key importance, as suppressing errors is central to the reliable operation of all quantum technologies. Their methods could eventually be applied to larger quantum networks, potentially facilitating their future deployment in real-world settings.

“Over the past 10 years, our team has gradually developed various tools for achieving this goal, including individual control of electron spins, nuclear spins, and single photons associated with a nitrogen-vacancy center,” explained Hou.

“We have also entangled the electron spins with nearby nuclear spins and single photons separately. Recent approaches combine these developed techniques and demonstrate the ability to control them all with relatively high fidelity. “

This team’s latest research efforts represent an additional step towards the realization of scalable quantum networks that operate reliably with minimal errors, which could in turn fuel advances in numerous fields. For instance, these networks could help to speed up communications, enhance sensing and support some complex computations that cannot be performed by classical computing systems.

“Our plan for future research is to include more qubits to correct both bit-flip and phase-flip errors, and to further improve the system performance, such as detection fidelity,” added Hou. “Once we are satisfied with the performance of a single node, we may set up one or two more systems and make a small-scale quantum network.”

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