Quantum network with two kinds of atoms: Oxford keeps entanglement for over ten seconds
Physicists in Oxford entangle strontium and calcium ions at two separate locations. Calcium acts as memory and preserves the quantum state for more than ten seconds.
Archive image · Photo: Jpbowen / Wikimedia Commons, CC BY-SA 4.0 (cropped and resized)
Researchers at the University of Oxford have, for the first time, controlled entanglement between atoms of different elements in a quantum network. Each of two separate nodes holds one strontium ion and one calcium ion. The strontium ions are entangled with each other via light, and local operations then extend the entanglement to the calcium ions. This produced shared quantum states of up to four atoms. The work was published on 13 October in Physical Review Letters (DOI 10.1103/qpsf-nlp9).
The advantage of this division of labour: the calcium states used are less sensitive to magnetic-field noise than the strontium states that handle the network link. As a result, the lifetime of the entanglement increased from milliseconds to more than ten seconds.
"In this paper, we show for the first time that we can control the entanglement between different types of atoms," said lead author Dougal Main. According to co-author Gabriel Araneda, this could make future quantum networks useful for tasks in which several distant atoms need to share and preserve the same quantum state – for example quantum computing, more sensitive measurements across remote locations or comparisons between different types of atomic clocks.