Nanotechnology Now







Heifer International

Wikipedia Affiliate Button


DHgate

Home > Press > Entangled Photons from Quantum Dots

Abstract:
JQI Researchers Create Entangled Photons from Quantum Dots

News from the Public Affairs Office at the National Institute of Standards and Technology

Entangled Photons from Quantum Dots

College Park, MD | Posted on December 4th, 2009

To exploit the quantum world to the fullest, a key commodity is entanglement—the spooky, distance-defying link that can form between objects such as atoms even when they are completely shielded from one another.

Now, physicists at the Joint Quantum Institute have developed a promising new source of entangled photons using quantum dots tweaked with a laser. The JQI technique may someday enable more compact and convenient sources of entangled photon pairs than presently available for quantum information applications such as the distribution of "quantum keys" for encrypting sensitive messages.

Quantum dots are nanometer-scale bits of semiconductor—so small that electrical charges in the dots are confined in all directions. They can be made to emit photons—fluoresce—by pumping in energy to create so-called "excitons," a pairing of an electron and the electron-less "hole." When the electron falls back into the hole, the excess energy is released as a photon. Quantum dots can also host the even more exotic "biexciton," composed of two electrons and two holes.

When a short-lived biexciton decomposes, it undergoes two drops in energy, analogous to descending two rungs of a ladder, and a photon is released at each stage. Physicists have long been trying to use this process to get pairs of entangled photons from quantum dots. What makes entanglement possible is that the biexciton could decay along one of two possible pathways, analogous to two different ladders that both get it to the ground. During its descent it releases a pair of photons with a different kind of polarization (electric field direction) depending on the ladder it descends. If the energy drop at each stage is exactly the same in both pathways, so that the ladders look identical, the pathways become indistinguishable—and as a result the biexciton releases photons with undetermined polarization values. Measuring a photon would both determine its polarization and instantly define its partner's—a hallmark of entanglement.

But imperfections within the structure of the quantum dot create differences in the energy levels (rung heights) between the two pathways, making them distinguishable and creating photons with predetermined, clearly defined polarizations. Except in rare instances, this holds true even for the reliable, widely fabricated indium gallium arsenide (InGaAs) dots that JQI researcher Andreas Muller and his colleagues created at NIST. Muller and his coworkers solved this problem by beaming a laser at the quantum dot. The laser's electric field shifts the energy levels in one of the pathways so that the two pathways match up, resulting in the emission of entangled photons.

Entangled photons have come from individual quantum dots before but they have been spotted by hunting for dots in large samples whose imperfections accidentally gave the two pathways identical energy structure. JQI group leader Glenn Solomon says that this entanglement technique could work for a wide variety of quantum dots. Though the dots must be cooled to cryogenic temperatures, he adds that quantum dots could offer advantages as entanglement sources over their conventional crystal counterparts as they are less bulky and can conveniently produce one pair of entangled photons at a time, instead of in bunches.

A. Muller, W.F.Fang, J. Lawall and G.S. Solomon. "Creating polarization-entangled photons from a quantum dot." Upcoming in Physical Review Letters.

####

About Joint Quantum Institute, University of Maryland
The Joint Quantum Institute is a research partnership between University of Maryland (UMD) and the National Institute of Standards and Technology, with the support and participation of the Laboratory for Physical Sciences.

Created in 2006 to pursue theoretical and experimental studies of quantum physics in the context of information science and technology, JQI is located on UMD's College Park campus.

For more information, please click here

Contacts:
Media Contact at NIST
Ben Stein

(301) 975-3097

Copyright © National Institute of Standards and Technology

If you have a comment, please Contact us.

Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Bookmark:
Delicious Digg Newsvine Google Yahoo Reddit Magnoliacom Furl Facebook

Related News Press

News and information

Feynman Prize Winners Announced! April 26th, 2015

New ASTM Standards Will Help Educate Present and Future Nanotechnology Workforces April 26th, 2015

Heat makes electrons’ spin in magnetic superconductors April 26th, 2015

QD Vision Wins 2015 Bronze Edison Award for Color IQ™ Quantum Dot Technology April 26th, 2015

Possible Futures

Printing Silicon on Paper, with Lasers April 21st, 2015

A glass fiber that brings light to a standstill: By coupling photons to atoms, light in a glass fiber can be slowed down to the speed of an express train; for a short while it can even be brought to a complete stop April 9th, 2015

Nanotechnology in Medical Devices Market is expected to reach $8.5 Billion by 2019 March 25th, 2015

Nanotechnology Enabled Drug Delivery to Influence Future Diagnosis and Treatments of Diseases March 21st, 2015

Announcements

Feynman Prize Winners Announced! April 26th, 2015

New ASTM Standards Will Help Educate Present and Future Nanotechnology Workforces April 26th, 2015

Heat makes electrons’ spin in magnetic superconductors April 26th, 2015

QD Vision Wins 2015 Bronze Edison Award for Color IQ™ Quantum Dot Technology April 26th, 2015

Military

Electron spin brings order to high entropy alloys April 23rd, 2015

Engineer improves rechargeable batteries with MoS2 nano 'sandwich' April 18th, 2015

Cobalt film a clean-fuel find: Rice University discovery is efficient, robust at drawing hydrogen and oxygen from water April 15th, 2015

MIT sensor detects spoiled meat: Tiny device could be incorporated into 'smart packaging' to improve food safety April 15th, 2015

Quantum Dots/Rods

QD Vision Wins 2015 Bronze Edison Award for Color IQ™ Quantum Dot Technology April 26th, 2015

QD Vision Expands Product Line with Two-Millimeter Color LCD Display Optic: Color IQ™ Optic Enables Full-Color Gamut for Ultra-Thin Displays and All-in-One Computers April 16th, 2015

Promising future of quantum dots explored in conference: ‘20 Years of Quantum Dots at Los Alamos’ runs April 12-16 April 13th, 2015

Next important step toward quantum computer: Scientists at the University of Bonn have succeeded in linking 2 different quantum systems March 30th, 2015

Quantum nanoscience

Quantum 'paparazzi' film photons in the act of pairing up April 22nd, 2015

From metal to insulator and back again April 22nd, 2015

Quantum model reveals surface structure of water: National Physical Laboratory, IBM and Edinburgh University have used a new quantum model to reveal the molecular structure of water's liquid surface April 20th, 2015

Quantization of 'surface Dirac states' could lead to exotic applications April 15th, 2015

NanoNews-Digest
The latest news from around the world, FREE




  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoTech-Transfer
University Technology Transfer & Patents
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More










ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project