Entanglement, the spooky link that makes disparate quantum objects act as one, can now be topped up for as long as necessary.
In recent years, physicists have learned to exploit entanglement to communicate, compute and even teleport. But these experiments have always been hard because entanglement rapidly leaks into the environment. Blink and it's gone.
Now Hanna Krauter at the Niels Bohr Institute in Copenhagen and colleagues have worked out how to entangle two clouds of caesium atoms and maintain the link for as long as they keep their experiment running.
The team bathe both clouds of atoms in a laser beam, which simultaneously aligns their collective spins. This entangles the clouds. But the clouds emit photons, which allow the entanglement to leak away. Their trick, described in a paper to appear in Physical Review Letters, is to replenish the entanglement as it escapes.
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