FEB 21, 2020 9:28 AM PST

Down the 50km Quantum Memory Lane: Scientists Push the Limit of Quantum Communication

WRITTEN BY: Daniel Duan

(Pixabay)

Quantum communication is also known as the "unhackable" way of transmitting any information. Deeply rooted in quantum mechanics, the state-of-the-art form of communication can empower a super-fast, super-secure global network. 

According to a recent report, a team of scientists at the University of Science and Technology of China (Hefei, China) succeeded in maintaining the entanglement of two quantum memories in fiber optic cables that are over 50 kilometers (31 miles) long. This record-breaking feat surpassed the current limit by almost 50 times.

At the core of quantum communication lies quantum entanglement, a phenomenon involving two particles connected and reliant on each other (also known as the entanglement state), even though they could be light-years apart. 

Say the two particles are photons used to encrypt quantum computer memory (which make them quantum memory), as long as they can stay in the entanglement state, they can store the information in a secretive, quantum state for later retrieval. In contrast, a current computing memory stores information as "1" s and "0" s (bits), giving hackers a wide-open window to intercept the transimission. 

Two years ago, the same group led by Jian-Wei Pan, a revered quantum information expert, set another world record by relaying entangled photon particles at two locations that are 1,200 km (750 mi) apart from each other, using their Quantum Experiments at Space Scale satellite.

Quantum satellite achieves 'spooky action' at record distance (Science)

Before this work, the current maximal distance for transmitting entangled quantum memories was 1.3 km, achieved by a team of European scientists back in 2015.
 
The Chinese group was looking to push the distance limit by adding a different kind of entanglement: they use a technique as cavity enhancement to create atom-photon entanglement. They passed the encrypted quantum memory through successive nodes in their fiber networks, where the nodes provide immobile atoms, and the photons serve as the message carrier. 

In the end, they achieved maintaining entanglement of two quantum memories through 22 km-long fiber cable with two-photon interference, and over 50 km of via single-photon interference. 

"The main significance of this paper lies in extending the entangling distance in (optical) fiber between quantum memories to the city scale," said Jian-Wei Pan, the senior author of the said report and a member of Chinese Academy of Science, in an interview with the Australian Broadcasting Corporation.

The Chinese team published their record-breaking study in the journal Nature.

Source: Science Alert

About the Author
Graduated with a bachelor degree in Pharmaceutical Science and a master degree in neuropharmacology, Daniel is a radiopharmaceutical and radiobiology expert based in Ottawa, Canada. With years of experience in biomedical R&D, Daniel is very into writing. He is constantly fascinated by what's happening in the world of science. He hopes to capture the public's interest and promote scientific literacy with his trending news articles. The recurring topics in his Chemistry & Physics trending news section include alternative energy, material science, theoretical physics, medical imaging, and green chemistry.
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