In the laboratory of Oxford University, two groups of strontium and calcium ions, separated by optical fibers, preserved quantum entanglement for more than ten seconds. This is not just a record — it is the first case in which remote entanglement has been successfully "transferred" into long-term atomic memory within a distributed network.
The team led by Gabriel Araneda used two nodes. Each contained one strontium ion and one calcium ion, held by electromagnetic fields. The strontium ions emitted photons, which were collected at a central station and measured according to the Bell protocol. A coincidence of detections meant that the strontium ions had become entangled over a distance. Then the entanglement was transferred to the calcium ions — their states turned out to be less sensitive to magnetic noise.
Imagine two coins that always land the same side up, even if they were tossed in different cities and no one was watching. That is exactly how entanglement behaves: the state of one particle instantly determines the state of the other, regardless of distance. Here, moreover, this state was "frozen" in the calcium ions so that it would not decay within milliseconds.
As a result, the researchers obtained entangled states involving up to four ions of two different elements, distributed between two nodes. The storage time in the calcium memory exceeded ten seconds — orders of magnitude longer than that of network qubits on strontium. The work was published in Physical Review Letters on 21 October 2026.
This opens the way to distributed quantum computers, where individual processors work together as a single system, to remote quantum sensors, and to the comparison of atomic clocks. The next step is more complex protocols with error correction and secure quantum communication.
Such memory turns ephemeral quantum communication into a stable resource that can be managed and stored.
