Australasian Science: Australia's authority on science since 1938

Quantum Entanglement Secured

A team of Australian and New Zealand physicists has extended the storage time for a quantum hard drive prototype by a factor of more than 100.

The record storage time of 6 hours, reported in Nature, is a major step towards a secure worldwide data encryption network based on quantum information that could be used for banking transactions and other information requiring secure data transmission.

The physicists stored quantum information in atoms of the rare earth element europium embedded in a crystal. After writing a quantum state onto the nuclear spin of the europium using laser light, the team subjected the crystal to a combination of fixed and oscillating magnetic fields to preserve the fragile quantum information.

“The two fields isolate the europium spins and prevent the quantum information leaking away,” said Dr Jevon Longdell of the University of Otago.

It has long been hoped that scientists will eventually come up with a way to store data in a state of quantum entanglement, but such states can only be maintained for a short time before the entanglement fails. “Quantum states are very fragile and normally collapse in milliseconds,” says lead author Ms Manjin Zhong of the Australian National University.

“Our goal is to extend this storage time out past a day,” Longdell continues. “Once we reach this target we believe it will be possible to physically distribute entangled quantum states between any two points on the globe.”

While photonic systems can currently create quantum networks around 100 km long, Zhong says “we can now imagine storing entangled light in separate crystals and then transporting them to different parts of the network thousands of kilometres apart. So, we are thinking of our crystals as portable optical hard drives for quantum entanglement.”