For years, the idea of a true quantum internet has sounded more like a theoretical promise than something engineers could actually build. That is because one stubborn bottleneck kept getting in the way. Quantum nodes could usually create entanglement only one fragile link at a time, making large scale networks painfully slow. Now, researchers at Caltech have demonstrated a breakthrough that many believed was out of reach.
According to a study published in Nature, Andrei Faraon, a professor at California Institute of Technology and his team successfully linked two quantum processors in a way that allows multiple atomic connections to share entanglement at the same time, rather than sequentially. This approach, known as entanglement multiplexing, dramatically increases how fast quantum information can be shared between nodes.
In simple terms, quantum entanglement is the strange phenomenon where two particles become linked so that measuring one instantly affects the other, no matter how far apart they are. It is the backbone of any future quantum internet, promising ultra secure communication and new forms of distributed computing. Until now, most experimental quantum links relied on a single qubit in each node. Each entanglement attempt had to be prepared, tested, and reset before trying again, which severely limited speed.
The Caltech experiment changes that model. Each node in their network is a tiny nanofabricated chip containing around twenty ytterbium atoms, each acting as its own qubit. Instead of treating differences between these atoms as a problem, the researchers used them as separate channels. Slight variations in the atoms’ optical properties allow multiple entangled links to be attempted in parallel.
The key enabling technique is called quantum feed-forward control. Detectors at a central station monitor when photons from each node arrive and which detectors register a signal. That timing information is immediately fed back into the system, allowing precise quantum operations to be applied to the correct atoms. This ensures the shared quantum state ends up in the desired entangled form, even when photons are not perfectly identical.
Using this method, the team not only created multiple entangled pairs simultaneously, but also demonstrated a more complex three particle W state. In this type of entanglement, a single shared excitation is distributed across several atoms. These multipartite states are especially valuable for advanced quantum networking tasks like routing information securely across multiple nodes.
The hardware itself is also notable. The nodes are built from rare earth ions embedded in nanophotonic cavities. Because the relevant electrons in these atoms are well shielded from their environment, they can store quantum information longer than many other solid state systems. The tiny cavities enhance light emission, making it easier to send photons between nodes.
While this network exists only in a lab and spans just two nodes, the implications are much larger. The same architecture could scale to many nodes, each hosting dozens or even hundreds of qubits. With additional steps like converting photons to telecom wavelengths, such systems could eventually communicate over long distances using existing fiber networks.
The study, published in Nature, marks a shift in how scientists think about building quantum networks. Instead of fighting imperfections and complexity, the Caltech team showed that those very differences can be harnessed to unlock faster, more flexible quantum communication. It does not mean a global quantum internet is imminent, but it does remove one of the biggest technical roadblocks standing in the way.