Breakthrough in quantum networks: three remote atomic qubits entangled for the first time
The world of quantum technologies is taking another significant step forward. A research group, combining efforts from Duke University and IonQ, has announced the creation of the first fully distributed three-node quantum network of its kind. The key achievement is the formation of the so-called Greenberger-Horne-Zeilinger (GHZ) state among three remote quantum nodes connected by photonic channels.
Essence of the Experiment
Quantum entanglement is a phenomenon where multiple particles remain inextricably linked, regardless of the distance between them. A change in the state of one particle instantly affects the others, making this effect a fundamental basis for future quantum networks and the quantum internet.
Previously, scientists had demonstrated entanglement between two remote nodes and even three-node networks on other physical platforms. However, this is the first time such a result has been achieved specifically for individual atomic qubits. These qubits can be independently controlled, read out, and, critically, scaled to build computational systems.
Why This Is a Breakthrough
The main challenge for modern quantum computers is scaling. Building a single large quantum processor is extremely difficult due to error accumulation and hardware limitations. That is why more and more developers are betting on a modular architecture: instead of one giant computer, a network of many quantum nodes connected by photons is created. This approach resembles the development of the classical internet, where computing resources are distributed across many servers.
The new experiment is a crucial step precisely in this direction. The researchers showed that individual atomic memories can form a shared quantum state through photonic connections while maintaining high fidelity of quantum operations.
During the experiment, the scientists achieved a fidelity of the entangled state at the level of 84–88%. Moreover, for the first time, they managed to close the so-called "detection loophole" for a fully distributed multi-component quantum state. The results also confirmed the violation of the Mermin inequality — one of the key tests demonstrating the presence of genuine quantum correlations.
Path to the Quantum Internet
This work continues a series of studies by the IonQ team in the field of photonic quantum connections. Previously, the company's specialists demonstrated entanglement between two remote ion systems, and now they have expanded the architecture to three full nodes.
Although the technology is still far from commercial application, such experiments are considered crucial building blocks for future distributed quantum computers, secure communication networks, and the quantum internet.
Expert Opinion: This experiment is not just a demonstration of capabilities, but practical proof that the modular approach to building quantum systems is viable. Closing the "detection loophole" is especially important, as it eliminates one of the main arguments of skeptics regarding the unreliability of quantum correlations in distributed networks. We are witnessing fundamental science turning into engineering reality.