Jennifer Leman* says scientists have observed entanglement in two quantum memories — a big step in creating an ultra-secure quantum computing network.
Quantum entanglement has mystified physicists for more than a century and is the cornerstone of quantum communication.
Entanglement establishes a mysterious connection between two particles even when they are separated by great distances.
As scientists work to entangle larger and larger particles — across greater and greater distances — it can be difficult to maintain a connection between them.
That’s where quantum memories come in.
Quantum memories, impossibly small bundles of rubidium atoms, capture and store quantum information and will be a critical piece of infrastructure in the development of quantum communication.
In this experiment, each quantum memory was composed of approximately 100 million laser-frozen rubidium atoms, chilling in a vacuum chamber.
The longest distance between two entangled quantum memories had previously been about 1.3 km.
But now, a team of Chinese researchers from the University of Science and Technology of China have broken that record.
They reported the results of their experiments in the journal Nature.
Scientists prodded the atomic clouds with lasers, sparking a photon to shoot off through the fibre-optic cables.
In one experiment, the researchers were able to transmit the photons across a roughly 21-km-long fibre-optic cable buried underground.
In the other experiment, entanglement occurred across a more than 48-km-long cable, which was coiled up in the lab.
From a third location, the scientists performed a Bell measurement, an observation which catches entanglement in the act, on the two photons that were paired with their respective memory.
Scientists have beamed single, entangled photons from even greater distances.
In 2017, researchers sent pairs of entangled photons from a Chinese satellite across a distance of almost 1,050 km to a ground station on Earth.
The goal of quantum computing is to provide a rapid, secure connection that can instantly send packets of quantum information to computers around the world.
The beauty of it is that it’s unhackable — a quality many world leaders find incredibly desirable.
In October, Google announced that it had finally achieved quantum supremacy with its quantum computer chip called Sycamore, which they say within a matter of minutes untangled a fantastically challenging problem that the world’s fastest supercomputers couldn’t solve in less than 10,000 years (though IBM challenged this claim).
While this latest research is an important step in getting quantum communication off the ground, researchers have a long way to go before the technology becomes mainstream.
“Honestly, there is still a long way to go in order to see the quantum repeater working in real long-distance situations,” scientist Xiao-Hui Bao, who led the team, told New Scientist.
* Jennifer Leman is a science journalist and editor. She tweets at @jlorileman. Her website is jenniferleman.com.
This article first appeared at www.popularmechanics.com/science.
