Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Physicists demonstrate storage and retrieval of single photons between remote memories

08.12.2005


Quantum memory



A series of publications in the journal Nature highlights the race among competing research groups toward the long-anticipated goal of quantum networking.

In one of three papers published the journal’s December 8 issue, a group of physicists from the Georgia Institute of Technology led by Professors Alex Kuzmich and Brian Kennedy describes the storage and retrieval of single photons transmitted between remote quantum memories composed of rubidium atoms. The work represents a significant step toward quantum communication and computation networks that would store and process information using both photons and atoms.


But the researchers caution that even with their rudimentary network operation, practical applications for quantum networking remain a long way off.

"The controlled transfer of single quanta between remote quantum memories is an important step toward distributed quantum networks," said Alex Kuzmich, the Cullen-Peck Assistant Professor in Georgia Tech’s School of Physics. "But this is still a building block. It will take a lot of steps and several more years for this to happen in a practical way."

Slightly more than a year ago in a paper published in the journal Science, Kuzmich and collaborator Dzmitry Matsukevich described transferring atomic state information from two different clouds of rubidium atoms onto a single photon. That work was the first time that quantum information had been transferred from matter to light.

In the new paper in Nature, Kuzmich, Kennedy and collaborators Thierry Chaneliere, Dzmitry Matsukevich, Stewart Jenkins, Shau-Yu Lan carry the earlier operation one step farther by storing and retrieving single photons from clouds of ultra-cold rubidium atoms – demonstrating the storage of light-based information in matter.

From an applications perspective, the storage and retrieval of a qubit state in an atomic quantum memory node is an important step towards a "quantum repeater." Such a device would be necessary for transmitting quantum information long distances through optical fibers.

Existing telecommunications networks use classical light to transmit information through optical fibers. To carry information long distances, such signals must be periodically boosted by repeater stations that cannot be used for quantum networking.

The Georgia Tech researchers began their experiment by exciting a cloud of rubidium atoms stored in a magneto-optical trap at temperatures approaching absolute zero. The excitation can generate a photon – but only infrequently, perhaps once every five seconds. Because it is in resonance with the atoms from which it was created, the photon carries specific quantum information about the excitation state of the atoms.

The photon was sent down approximately 100 meters of optical fiber to a second very cold cloud of trapped rubidium atoms. The researchers controlled the velocity of the photon in the second cloud by an intense control laser beam. Once the photon was inside the cloud, the control beam was switched off, allowing the photon to come to a halt inside the dense ensemble of atoms.

"The information from the photon is stored in the state of excitation of many atoms of the second ensemble," explained Jenkins, a graduate student who specializes in quantum optics theory. "Each atom in the ensemble is slightly flipped, so the atomic ensemble is sharing this information – which is really information about spin."

After allowing the photon to be stored in the atomic cloud for time periods that exceeded 10 microseconds, the control beam was turned back on, allowing the photon to re-emerge from the atomic cloud. The researchers then compared the quantum information carried on the photon to verify that it matched the information carried into the cloud.

"When the single photon is generated, the first atomic ensemble is in an excited state," explained Chaneliere, a postdoctoral fellow in the Kuzmich lab. "When we read the information from the second ensemble and find a coincidence between its excitation and the excitation of the first ensemble, we have demonstrated storage of the photon."

To confirm the single photon character of the storage, the researchers used anti-correlation measurements involving three single photon detectors.

Storage of the photon for even a brief period of time within the atomic ensemble depends on careful control of potentially-interfering magnetic fields. And it works only because the rubidium atoms are so cold that their motion is limited.

"Quantum information is very fragile," said Chaneliere. "If you have a magnetic field, the atoms spin out of phase, and you can lose the information. For the moment, that is certainly a limitation on the use of this for quantum networking."

For the future, the team hopes to add additional nodes to their rudimentary quantum network and encode useful information onto their photons.

They must also increase the probability of creating single photons from the first atomic cloud. While gathering data, the researchers excited the first cloud of atoms approximately 200 times a second. A single photon was created about once every five seconds, reported Matsukevich, a graduate student in the Kuzmich lab.

Highlighting the speed at which progress is being made toward quantum networking, Kuzmich, Kennedy and their team have more recently demonstrated entanglement between two atomic qubits separated by a distance of 5.5 meters. The work is described in a paper submitted to the journal Physical Review Letters.

"This entanglement would be important to a number of applications, including quantum cryptography," said Kuzmich. "We have generated entanglement of atomic qubits. We also showed that we can take this entanglement and map it from atoms to photons."

John Toon | EurekAlert!
Further information:
http://www.edi.gatech.edu

More articles from Physics and Astronomy:

nachricht Smallest transistor worldwide switches current with a single atom in solid electrolyte
17.08.2018 | Karlsruher Institut für Technologie (KIT)

nachricht Protecting the power grid: Advanced plasma switch for more efficient transmission
17.08.2018 | DOE/Princeton Plasma Physics Laboratory

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: It’s All in the Mix: Jülich Researchers are Developing Fast-Charging Solid-State Batteries

There are currently great hopes for solid-state batteries. They contain no liquid parts that could leak or catch fire. For this reason, they do not require cooling and are considered to be much safer, more reliable, and longer lasting than traditional lithium-ion batteries. Jülich scientists have now introduced a new concept that allows currents up to ten times greater during charging and discharging than previously described in the literature. The improvement was achieved by a “clever” choice of materials with a focus on consistently good compatibility. All components were made from phosphate compounds, which are well matched both chemically and mechanically.

The low current is considered one of the biggest hurdles in the development of solid-state batteries. It is the reason why the batteries take a relatively long...

Im Focus: Color effects from transparent 3D-printed nanostructures

New design tool automatically creates nanostructure 3D-print templates for user-given colors
Scientists present work at prestigious SIGGRAPH conference

Most of the objects we see are colored by pigments, but using pigments has disadvantages: such colors can fade, industrial pigments are often toxic, and...

Im Focus: Unraveling the nature of 'whistlers' from space in the lab

A new study sheds light on how ultralow frequency radio waves and plasmas interact

Scientists at the University of California, Los Angeles present new research on a curious cosmic phenomenon known as "whistlers" -- very low frequency packets...

Im Focus: New interactive machine learning tool makes car designs more aerodynamic

Scientists develop first tool to use machine learning methods to compute flow around interactively designable 3D objects. Tool will be presented at this year’s prestigious SIGGRAPH conference.

When engineers or designers want to test the aerodynamic properties of the newly designed shape of a car, airplane, or other object, they would normally model...

Im Focus: Robots as 'pump attendants': TU Graz develops robot-controlled rapid charging system for e-vehicles

Researchers from TU Graz and their industry partners have unveiled a world first: the prototype of a robot-controlled, high-speed combined charging system (CCS) for electric vehicles that enables series charging of cars in various parking positions.

Global demand for electric vehicles is forecast to rise sharply: by 2025, the number of new vehicle registrations is expected to reach 25 million per year....

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

LaserForum 2018 deals with 3D production of components

17.08.2018 | Event News

Within reach of the Universe

08.08.2018 | Event News

A journey through the history of microscopy – new exhibition opens at the MDC

27.07.2018 | Event News

 
Latest News

Quantum bugs, meet your new swatter

20.08.2018 | Information Technology

A novel synthetic antibody enables conditional “protein knockdown” in vertebrates

20.08.2018 | Life Sciences

Metamolds: Molding a mold

20.08.2018 | Information Technology

VideoLinks
Science & Research
Overview of more VideoLinks >>>