Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Advancing secure communications: A better single-photon emitter for quantum cryptography

10.04.2013
In a development that could make the advanced form of secure communications known as quantum cryptography more practical, University of Michigan researchers have demonstrated a simpler, more efficient single-photon emitter that can be made using traditional semiconductor processing techniques.

Single-photon emitters release one particle of light, or photon, at a time, as opposed to devices like lasers that release a stream of them. Single-photon emitters are essential for quantum cryptography, which keeps secrets safe by taking advantage of the so-called observer effect: The very act of an eavesdropper listening in jumbles the message. This is because in the quantum realm, observing a system always changes it.

For quantum cryptography to work, it's necessary to encode the message—which could be a bank password or a piece of military intelligence, for example—just one photon at a time. That way, the sender and the recipient will know whether anyone has tampered with the message.

While the U-M researchers didn't make the first single-photon emitter, they say their new device improves upon the current technology and is much easier to make.

"This thing is very, very simple. It is all based on silicon," said Pallab Bhattacharya, the Charles M. Vest Distinguished University Professor of Electrical Engineering and Computer Science, and the James R. Mellor Professor of Engineering.

Bhattacharya, who leads this project, is a co-author of a paper on the work published in Nature Communications on April 9.

Bhattacharya's emitter is a single nanowire made of gallium nitride with a very small region of indium gallium nitride that behaves as a quantum dot. A quantum dot is a nanostructure that can generate a bit of information. In the binary code of conventional computers, a bit is a 0 or a 1. A quantum bit can be either or both at the same time.

The semiconducting materials the new emitter is made of are commonly used in LEDs and solar cells. The researchers grew the nanowires on a wafer of silicon. Because their technique is silicon-based, the infrastructure to manufacture the emitters on a larger scale already exists. Silicon is the basis of modern electronics.

"This is a big step in that it produces the pathway to realizing a practical electrically injected single-photon emitter," Bhattacharya said.

Key enablers of the new technology are size and compactness.

"By making the diameter of the nanowire very small and by altering the composition over a very small section of it, a quantum dot is realized," Bhattacharya said. "The quantum dot emits single-photons upon electrical excitation."

The U-M emitter is fueled by electricity, rather than light—another aspect that makes it more practical. And each photon it emits possesses the same degree of linear polarization. Polarization refers to the orientation of the electric field of a beam of light. Most other single-photon emitters release light particles with a random polarization.

"So half might have one polarization and the other half might have the other," Bhattacharya said. "So in cryptic message, if you want to code them, you would only be able to use 50 percent of the photons. With our device, you could use almost all of them."

This device operates at cold temperatures, but the researchers are working on one that operates closer to room temperature.

The paper is titled "Electrically-driven polarized single-photon emission from an InGaN quantum dot in a GaN nanowire." The first author is Saniya Deshpande, a graduate student in electrical engineering and computer science. The work is supported by the National Science Foundation. The device was fabricated at the U-M Lurie Nanofabrication Facility.

Pallab Bhattacharya:
https://www.eecs.umich.edu/eecs/etc/fac/facsearchform.cgi?pkb+

Nicole Casal Moore | EurekAlert!
Further information:
http://www.umich.edu

More articles from Physics and Astronomy:

nachricht Light-emitting bubbles captured in the wild
28.02.2017 | Georg-August-Universität Göttingen

nachricht Scientists reach back in time to discover some of the most power-packed galaxies
28.02.2017 | Clemson University

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: Safe glide at total engine failure with ELA-inside

On January 15, 2009, Chesley B. Sullenberger was celebrated world-wide: after the two engines had failed due to bird strike, he and his flight crew succeeded after a glide flight with an Airbus A320 in ditching on the Hudson River. All 155 people on board were saved.

On January 15, 2009, Chesley B. Sullenberger was celebrated world-wide: after the two engines had failed due to bird strike, he and his flight crew succeeded...

Im Focus: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

New technology offers fast peptide synthesis

28.02.2017 | Life Sciences

WSU research advances energy savings for oil, gas industries

28.02.2017 | Power and Electrical Engineering

Who can find the fish that makes the best sound?

28.02.2017 | Information Technology

VideoLinks
B2B-VideoLinks
More VideoLinks >>>