Different kinds of atoms have shared a quantum state across two separate locations in an Oxford experiment. The researchers created entanglement involving up to four atoms, then used calcium atoms to preserve the connection for more than 10 seconds.
Oxford described the work on October 15, following its publication in Physical Review Letters on October 13. The experiment addresses a practical problem in quantum networks: making a connection is not enough if it disappears before other operations finish.
Entanglement links the properties of quantum particles. Networking separate processors requires that shared state to survive while operations take place at different sites.
At each location, the team held one strontium atom and one calcium atom. Light connected the strontium atoms across the network. Local operations then extended the shared state to calcium.
The two elements had different jobs. Strontium provided the network connection. Calcium offered a pair of states less sensitive to magnetic-field noise, which helped preserve the entanglement.
Oxford says transferring the state to calcium extended its lifetime from milliseconds to more than 10 seconds. That is a result from this controlled experiment, not the operating lifetime of a large commercial quantum network.
The work could support efforts to coordinate remote processors, compare atomic clocks or make linked measurements. Those are applications the researchers describe, rather than tasks shown at useful scale in this release.
The demonstration combines connections between different elements with longer storage of the shared state. It involved two locations and up to four atoms.
