Researchers from Duke University and the company IonQ have reported the creation of the first fully distributed three-node quantum network based on individual atomic qubits, Quantum Computing Report writes.

The specialists managed to form a so-called tripartite entangled state (Greenberger–Horne–Zeilinger state) between three remote quantum nodes linked by photonic channels.

What happened

Quantum entanglement allows several particles to remain linked regardless of the distance between them. A change in the state of one particle is instantly reflected in the state of the others, which makes this effect the foundation of future quantum networks and the quantum internet.

Until now, scientists had already demonstrated entanglement between two remote quantum nodes and even three-node networks on other physical platforms. However, this is the first time such a result has been achieved for individual atomic qubits, which can be independently controlled, read out and scaled to build computing systems.

Why it matters

The main problem of quantum computers is scaling. Building a single large quantum processor is extremely difficult because of errors and hardware limitations.

That is why many 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 classic internet, where computing resources are distributed among many servers.

The new experiment was a step in precisely this direction. The researchers showed that individual atomic memories can form a shared quantum state through photonic connections while preserving high accuracy of quantum operations.

During the experiment the scientists achieved a fidelity of the entangled state of 84–88% and, for the first time, closed the so-called «detection loophole» for a fully distributed multipartite quantum state. In addition, the results confirmed a violation of the Mermin inequality — one of the key tests demonstrating the presence of genuine quantum correlations.

A step toward the quantum internet

The work continues the IonQ team's series of studies in the field of photonic quantum connections. Earlier the company's specialists demonstrated entanglement between two remote ion systems, and now they have expanded the architecture to three full-fledged nodes.

Although the technology is still far from commercial use, such experiments are considered important building blocks of future distributed quantum computers, secure communication networks and the quantum internet.

Recall that in June Colt Technology Services and Ciena successfully tested data transmission with quantum-resistant encryption between New York and London.

Source: ForkLog