A quantum network using atomic qubits: three-way entanglement achieved for the first time
A research team from Duke University, in collaboration with engineers from IonQ, has announced a breakthrough in the field of distributed quantum computing. They have, for the first time, successfully formed a three-party entangled state — the so-called Greenberger-Horne-Zeilinger (GHZ) state — between three remote atomic qubits connected via photonic channels.
Quantum entanglement is a fundamental phenomenon where a change in the state of one particle instantly affects the state of another, regardless of the distance between them. This effect is the foundation of future quantum networks and the quantum internet. Previously, two-party entanglement between remote nodes had already been demonstrated, as had three-node networks on other physical platforms. However, this case involves individual atomic qubits that can be independently controlled and read out, which is critically important for building scalable computing systems.
Why This Is a Breakthrough
The main headache for the quantum industry is scaling. Creating a single giant quantum processor with zero error rates is practically impossible. Therefore, more and more developers are moving toward a modular architecture: instead of a monolithic computer, a network of many quantum nodes connected by photons is built. This resembles the evolution of the classical internet, where resources are distributed across thousands of servers.
The new experiment is a direct step in this direction. The researchers showed that individual atomic memories can form a common quantum state through photonic connections while maintaining high operational fidelity. During tests, the fidelity of the entangled state reached 84–88%. Additionally, 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 for genuine quantum correlations.
A Step Toward the Quantum Internet
This work continues a series of IonQ studies on photonic quantum connections. Previously, the company demonstrated entanglement between two remote ion systems, and now it has expanded the architecture to three full-fledged nodes. Although the technology is still far from commercial implementation, such experiments lay the foundation for distributed quantum computers, secure communication networks, and, ultimately, the quantum internet.
My analysis: Achieving 84–88% fidelity for a three-node network on atomic qubits is an impressive result, especially with the closure of the "detection loophole." However, for practical application, not only will an increase in accuracy to 99%+ be required, but also solving the problem of decoherence when scaling to dozens and hundreds of nodes. Nevertheless, this is a clear signal to the market: modular architecture on atomic qubits is becoming a real alternative to superconducting solutions.