Featured Research

from universities, journals, and other organizations

Quantum optical link sets new time records

Date:
August 19, 2011
Source:
University of Copenhagen
Summary:
Quantum communication could be an option for absolutely secure transfer of data. The key component in quantum communication over long distances is entanglement between two atomic systems. Entanglement is very fragile and until now researchers have only been able to maintain the entanglement for a fraction of a second. But researchers have now succeeded in maintaining the entanglement for up to an hour.

The image shows the two clouds of caesium atoms. The atoms have been entangled using laser light. The atoms spontaneously emit photons in all directions. By designing the experiment in a very precise way the NBI team succeeded in maintaining the entanglement for up to an hour.
Credit: Christine Muschik

Quantum communication could be an option for the absolutely secure transfer of data. The key component in quantum communication over long distances is the special phenomenon called entanglement between two atomic systems. Entanglement between two atomic systems is very fragile and up until now researchers have only been able to maintain the entanglement for a fraction of a second. But in new experiments at the Niels Bohr Institute researchers have succeeded in setting new records and maintaining the entanglement for up to an hour.

Related Articles


The results are published in the scientific journal Physical Review Letters.

Entanglement is a curious phenomenon in quantum mechanics which Albert Einstein called "spukhafte Fernwirkung" (spooky action at a distance). Two separate entangled systems have a ghostlike connection even when they are placed at a large distance without being directly connected to each other. It is said that their states are correlated. This means that if you read out the one system, the other system will 'know' about it. In the experiments at the Niels Bohr Institute, the spins of two gas clouds of caesium atoms are entangled.

Control of a spontaneous process

To create the entangled state of the two atomic clouds the researchers use light. Light consists of photons, which are the smallest parts (a quantum) of a light pulse. When you shine a laser beam on atoms the photons are absorbed and subsequently re-emitted spontaneously. This process has been an impediment to the experiments because it is uncontrolled.

"Now we have managed to control this 'spontaneous' process and use it," explains Eugene Polzik, Professor and Director of the Danish National Research Foundation Center, Quantop at the Niels Bohr Institute at the University of Copenhagen.

Maintaining entanglement

In the Quantop laboratories the research group conducted experiments with entanglement using two clouds of caesium atoms placed in separate glass containers. By illuminating both clouds of atoms with laser light, the collective spins of the atoms are manipulated. The two atomic clouds become entangled, which means that some of their properties are correlated.

But the atoms emit photons in all directions and this causes the entanglement to disappear. This usually happens in a fraction of a second.

"What we have done is that we have developed a technique where we renew the entanglement as fast as it disappears. In this way we have been able to maintain the entanglement between the two atomic clouds as long as the experiment lasted, that is to say up to an hour," explains Hanna Krauter, who is a quantum physicist and researcher at Quantop at the Niels Bohr Institute.

From theory to reality

The research has been conducted in collaboration with the Max Planck Institute of Quantum Optics in Germany, where they have been working with the theoretical models. Theoretical physicists have suggested similar techniques for about five years, but it is only now that the NBI team has succeeded in conducting the physical experiments based on these methods and getting them to work.

"The breakthrough has great potential and provides, among other things, a new approach to quantum communication. It is a step towards getting quantum communication to function in practice -- not just in the laboratory, but also in the real world of networking la the Internet. In addition, it means an improvement of ultra-precise measurements of miniscule magnetic fields with atomic magnetometers. Sensitive magnetometers could be used to measure electrical activity in the human brain and heart," explains Professor Eugene Polzik.


Story Source:

The above story is based on materials provided by University of Copenhagen. Note: Materials may be edited for content and length.


Journal Reference:

  1. Hanna Krauter, Christine A. Muschik, Kasper Jensen, Wojciech Wasilewski, Jonas M. Petersen, J. Ignacio Cirac, and Eugene S. Polzik. Entanglement Generated by Dissipation and Steady State Entanglement of Two Macroscopic Objects. Physical Review Letters, Volume 107, Issue 8 DOI: 10.1103/PhysRevLett.107.080503

Cite This Page:

University of Copenhagen. "Quantum optical link sets new time records." ScienceDaily. ScienceDaily, 19 August 2011. <www.sciencedaily.com/releases/2011/08/110817094920.htm>.
University of Copenhagen. (2011, August 19). Quantum optical link sets new time records. ScienceDaily. Retrieved March 6, 2015 from www.sciencedaily.com/releases/2011/08/110817094920.htm
University of Copenhagen. "Quantum optical link sets new time records." ScienceDaily. www.sciencedaily.com/releases/2011/08/110817094920.htm (accessed March 6, 2015).

Share This


More From ScienceDaily



More Matter & Energy News

Friday, March 6, 2015

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Driverless Budii Gives the Wheel Feel

Driverless Budii Gives the Wheel Feel

Reuters - Business Video Online (Mar. 6, 2015) The Rinspeed Budii Concept car is creating a driverless stir at this year&apos;s Geneva car show. It&apos;s an all-electric autonomous vehicle with a difference. Ciara Lee reports. Video provided by Reuters
Powered by NewsLook.com
Star Wars Inspires Mobile Holograms

Star Wars Inspires Mobile Holograms

Reuters - Business Video Online (Mar. 6, 2015) 3D holograms could soon be coming to your mobile phone. Inspired by the famous Princess Leia hologram from Star Wars, a U.S. company is showcasing a prototype display at the Mobile World Congress at Barcelona and says it could be used for real-time video calls. Ivor Bennett reports Video provided by Reuters
Powered by NewsLook.com
Game Makers Lured Into Virtual Worlds

Game Makers Lured Into Virtual Worlds

AFP (Mar. 6, 2015) Some 25,000 people have descended upon San Francisco to show off the latest technologies and video games at the Game Developers Conference. Developers here discuss the future of the industry. Duration: 02:20. Video provided by AFP
Powered by NewsLook.com
Gas Production Cut on Earthquake Fears

Gas Production Cut on Earthquake Fears

Reuters - Business Video Online (Mar. 5, 2015) The Dutch government has cut production at Europe&apos;s largest gas field in Groningen amid concerns over earthquakes which are damaging local churches. As Amy Pollock reports the decision - largely politically-motivated - could have big economic conseqeunces. Video provided by Reuters
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Space & Time

Matter & Energy

Computers & Math

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins