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

Industrial Nanotech, Inc. Announces Next Large Order from the Oil and Gas Industry March 26th, 2015

Quantum compute this -- WSU mathematicians build code to take on toughest of cyber attacks: Revamped knapsack code offers online security for the future March 26th, 2015

Thousands of atoms entangled with a single photon: Result could make atomic clocks more accurate March 26th, 2015

Square ice filling for a graphene sandwich March 26th, 2015

Possible Futures

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

Nanocomposites Market Growth, Industry Outlook To 2020 by Grand View Research, Inc. March 21st, 2015

Nanotechnology Drug Delivery Market in the US 2012-2016 : Latest Report Available by Radiant Insights, Inc March 16th, 2015

Announcements

Industrial Nanotech, Inc. Announces Next Large Order from the Oil and Gas Industry March 26th, 2015

Quantum compute this -- WSU mathematicians build code to take on toughest of cyber attacks: Revamped knapsack code offers online security for the future March 26th, 2015

Thousands of atoms entangled with a single photon: Result could make atomic clocks more accurate March 26th, 2015

Square ice filling for a graphene sandwich March 26th, 2015

Military

Thousands of atoms entangled with a single photon: Result could make atomic clocks more accurate March 26th, 2015

Carbon nanotube fibers make superior links to brain: Rice University invention provides two-way communication with neurons March 25th, 2015

Tiny bio-robot is a germ suited-up with graphene quantum dots March 24th, 2015

UW scientists build a nanolaser using a single atomic sheet March 24th, 2015

Quantum Dots/Rods

Tiny bio-robot is a germ suited-up with graphene quantum dots March 24th, 2015

Rice fine-tunes quantum dots from coal: Rice University scientists gain control of electronic, fluorescent properties of coal-based graphene March 18th, 2015

Ghent University leads large-scale European training project on quantum dots March 13th, 2015

Optical nanoantennas set the stage for a NEMS lab-on-a-chip revolution February 24th, 2015

Quantum nanoscience

Thousands of atoms entangled with a single photon: Result could make atomic clocks more accurate March 26th, 2015

Bar-Ilan U. researchers identify 'tipping point' between quantum and classical worlds: Study sheds new light on 'spooky' quantum optics March 24th, 2015

Nanospheres cooled with light to explore the limits of quantum physics March 17th, 2015

Nanotechnology Helps Increasing Rate of Digital Data Processing, Storage March 9th, 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







© Copyright 1999-2015 7th Wave, Inc. All Rights Reserved PRIVACY POLICY :: CONTACT US :: STATS :: SITE MAP :: ADVERTISE