This article comes from WeChat public account: Academic Headline (ID: SciTouTiao)
In the early morning of February 13th, Beijing time, the latest issue of Nature published the latest results of the Pan Jianwei team at the University of Science and Technology of China: Two quantum memories are entangled remotely through optical fibers across tens of kilometers.
In this latest study, Pan Jianwei, Bao Xiaohui, and colleagues used a named cavity-enhanced quantum effect to make entangled atoms and photons, These entangled atoms and photons were then converted into frequencies suitable for telecommunications transmission, and finally entanglement was achieved between two nodes connected by 50 kilometers of fiber.
Research results show that Atomic-photon entanglement between multiple nodes may be more suitable for long-distance transmission of quantum entanglement than entangled photons.
This study demonstrates the entanglement of two quantum memories 50 km apart, a distance sufficient to connect two cities, and much farther than previously reported, or paved the way for multi-node, long-term entanglement. The road has helped the development of the quantum Internet.
Just like a hard drive in a computer, quantum storage stores quantum information. They are buildsA necessary part of the quantum internet and will facilitate the realization of ultra-secure quantum communications, allowing remote quantum computers to work together.
In the past, scientists have achieved entanglement of individual light particles 1200 kilometers apart, but this entanglement cannot be stored, and the maximum physical distance before quantum memory entanglement is only one kilometer away.
Breakthrough of remote entanglement
The realization of the quantum Internet connected to remote quantum processors will be able to support many revolutionary applications, such as distributed quantum computing. To achieve quantum communication, it is a key challenge to establish entanglement between remote quantum memories.
Although related research has made great progress, Due to severe transmission loss, the maximum achievable physical distance between two nodes was 1.3 kilometers, and there are still huge challenges to achieve long-term entanglement.
In order to extend the distance to the scale of the city, in this latest paper, researchers will use atomic group-based quantum storage and efficient quantum frequency conversion. (QFC ) combined and transmitted through tens of kilometers of urban-grade fiber optics to achieve entanglement of two quantum memories.
Schematic illustration of remote entanglement between sets of atoms, two quantum storage nodes (nodes A and B) are connected to a Intermediate station for photon measurement.
Specifically, researchers use cavity enhancement to create a bright source of atom-light quantum entanglement and use differential frequency generation ( DFG) Process Achieve low-loss transmission of optical fiber, and then achieve entanglement of atomic clusters over 22 kilometers through two-photon interference, and entanglement of atomic clusters over 50 kilometers through single-photon interference.
A bird’s eye view of the remote entanglement experiment. The two quantum nodes are located at the University of Science and Technology of China. The telecommunication photons from the two nodes are transmitted to the intermediate station in Hefei Software Park through two parallel deployed optical fibers.
This experiment proves two feasible methods to realize double quantum memory entanglement through long-distance photon transmission in optical fiber. Researchers said that by adding more quantum memories, the experimental results can be extended to entangle multiple quantum memories at long distances through multiphoton interference, and can also generate two pairs of remote atomic entanglements on two sublinks, According to the quantum relay scheme, the distance of entanglement of atoms is extended by entanglement exchange. This process in series can extend the distance sufficiently to exceed the limit of direct transmission.
Researchers believe that Extending these experiments to nodes that are far apart will be able to perform advanced quantum information tasks and pave the way for building large-scale quantum networks over long distances.
Quantum communication-the transmission process without shadows
Two particles in quantum entanglement, no matter how far apart, there is a mysterious relationship between them. This mysterious relationship cannot be understood by classic ideas anyway, which Einstein called “Strange interactions between distant places” .
Quantum information scientists have discovered that besides being mysterious, quantum entanglement is also a kind of ultra-classical power that can be used as a quantum computer with supercomputing power and a “foolproof” quantum security system The basics.
Quantum entanglement
According to common sense, the dissemination of information requires a carrier, and quantum communication does not require the carrier to transmit information.
Quantum teleportation is the use of quantum states as information carriers, and the transmission of large-capacity information through quantum state transmission is a kind of “complete” information transmission without physical objects, which can achieve complete confidentiality in principle < / strong>.
Quantum communication is a new communication method that uses the quantum entanglement effect to transfer information. It is a completely new communication method without shadows.
Based on quantum teleportation, the idea of quantum Internet has been proposed. Quantum Internet uses quantum channels to connect many quantum processors, which can simultaneously realize the transmission and processing of quantum information.
Compared to the classic Internet, Quantum Internet has a series of advantages such as security and confidentiality, which can realize multi-terminal distributed computing and effectively reduce communication complexity.
As one of the pioneers in the field of quantum information experimental research, Pan Jianwei is a scientist with important international influence in this field. In recent years, he has made a series of significant research results.
On August 16, 2016, the world’s first quantum scientific experimental satellite “Mozi” was successfully launched at the China Jiuquan Satellite Launch Center.
As the chief scientist of the “Mozi” quantum science experimental satellite, Pan Jianwei’s “Mozi” quantum science experimental satellite research team was awarded the 2018 Cleveland Award , which was also the establishment of the Cleveland Award For the first time in more than 90 years, the achievements of Chinese scientists in China have won this honor.
Mr. Pan Jianwei
After academician Pan Jianwei led the team to complete the quantum communication satellite scientific research project, he became famous both at home and abroad and is considered to be the top figure in the field of quantum communication in the world today. However, the reputation has also caused some controversy. Many folk scholars have questioned their achievements and even personal expressions. There are also sarcastic satires on the Internet.
In fact, Pan Jianwei ’s achievements in scientific research have left most scientific scholars untouched. During the period of Dr. Pan Jianwei, he studied under the world-class master of quantum experimental research Cai Linge. Selected as the “Top Ten Global Scientific and Technological Advancements of the Year” by the American “Science” magazine, and also rated as “21 Classic Papers in Physics in 100 Years” by Nature Academician, 45 years old, won the first prize of National Natural Science. In 2017, he was named one of the “Top Ten Scientific Persons of the Year in Nature” …
In any case, Pan Jianwei, who has the title of “Father of Quantum” in China, is still questioning the advance and keeping China in a leading position in the world of quantum communication.
Thesis title: Entanglement of two quantum memories via fibres over dozens of kilometres
Paper abstract:
Original paper:
https://nature.com/articles/s41586-020-1976-7
DOI: 10.1038 / s41586-020-1976-7
This article comes from WeChat public account: Academic Headline (ID: SciTouTiao)