Nanotechnology Now







Heifer International

Wikipedia Affiliate Button


DHgate

Home > Press > Researchers create quantum dots with single-atom precision

This image shows quantized electron states, for quantum numbers n = 1 to 6, of a linear quantum dot consisting of 22 indium atoms positioned on the surface of an InAs crystal.Image: Stefan Fölsch/PDI
This image shows quantized electron states, for quantum numbers n = 1 to 6, of a linear quantum dot consisting of 22 indium atoms positioned on the surface of an InAs crystal.

Image: Stefan Fölsch/PDI

Abstract:
A team of physicists from the Paul-Drude-Institut für Festkörperelektronik (PDI) in Berlin, Germany, NTT Basic Research Laboratories in Atsugi, Japan, and the U.S. Naval Research Laboratory (NRL) has used a scanning tunneling microscope to create quantum dots with identical, deterministic sizes. The perfect reproducibility of these dots opens the door to quantum dot architectures completely free of uncontrolled variations, an important goal for technologies from nanophotonics to quantum information processing as well as for fundamental studies. The complete findings are published in the July 2014 issue of the journal Nature Nanotechnology.

Researchers create quantum dots with single-atom precision

Washington, DC | Posted on June 30th, 2014

Quantum dots are often regarded as artificial atoms because, like real atoms, they confine their electrons to quantized states with discrete energies. But the analogy breaks down quickly, because while real atoms are identical, quantum dots usually comprise hundreds or thousands of atoms - with unavoidable variations in their size and shape and, consequently, in their properties and behavior. External electrostatic gates can be used to reduce these variations. But the more ambitious goal of creating quantum dots with intrinsically perfect fidelity by completely eliminating statistical variations in their size, shape, and arrangement has long remained elusive.

Creating atomically precise quantum dots requires every atom to be placed in a precisely specified location without error. The team assembled the dots atom-by-atom, using a scanning tunneling microscope (STM), and relied on an atomically precise surface template to define a lattice of allowed atom positions. The template was the surface of an InAs crystal, which has a regular pattern of indium vacancies and a low concentration of native indium adatoms adsorbed above the vacancy sites. The adatoms are ionized +1 donors and can be moved with the STM tip by vertical atom manipulation. The team assembled quantum dots consisting of linear chains of N = 6 to 25 indium atoms; the example shown here is a chain of 22 atoms.

Stefan Fölsch, a physicist at the PDI who led the team, explained that "the ionized indium adatoms form a quantum dot by creating an electrostatic well that confines electrons normally associated with a surface state of the InAs crystal. The quantized states can then be probed and mapped by scanning tunneling spectroscopy measurements of the differential conductance." These spectra show a series of resonances labeled by the principal quantum number n. Spatial maps reveal the wave functions of these quantized states, which have n lobes and n - 1 nodes along the chain, exactly as expected for a quantum-mechanical electron in a box. For the 22-atom chain example, the states up to n = 6 are shown.

Because the indium atoms are strictly confined to the regular lattice of vacancy sites, every quantum dot with N atoms is essentially identical, with no intrinsic variation in size, shape, or position. This means that quantum dot "molecules" consisting of several coupled chains will reflect the same invariance. Steve Erwin, a physicist at NRL and the team's theorist, pointed out that "this greatly simplifies the task of creating, protecting, and controlling degenerate states in quantum dot molecules, which is an important prerequisite for many technologies." In quantum computing, for example, qubits with doubly degenerate ground states offer protection against environmental decoherence. By combining the invariance of quantum dot molecules with the intrinsic symmetry of the InAs vacancy lattice, the team created degenerate states that are surprisingly resistant to environmental perturbations by defects. In the example shown here, a molecule with perfect three-fold rotational symmetry was first created and its two-fold degenerate state demonstrated experimentally. By intentionally breaking the symmetry, the team found that the degeneracy was progressively removed, completing the demonstration. The reproducibility and high fidelity offered by these quantum dots makes them excellent candidates for studying fundamental physics that is typically obscured by stochastic variations in size, shape, or position of the chains. Looking forward, the team also anticipates that the elimination of uncontrolled variations in quantum dot architectures will offer many benefits to a broad range of future quantum dot technologies in which fidelity is important.

####

About Naval Research Laboratory
The U.S. Naval Research Laboratory is the Navy's full-spectrum corporate laboratory, conducting a broadly based multidisciplinary program of scientific research and advanced technological development. The Laboratory, with a total complement of nearly 2,800 personnel, is located in southwest Washington, D.C., with other major sites at the Stennis Space Center, Miss., and Monterey, Calif. NRL has served the Navy and the nation for over 90 years and continues to meet the complex technological challenges of today's world. For more information, visit the NRL homepage or join the conversation on Twitter, Facebook, and YouTube.

For more information, please click here

Contacts:
Donna McKinney

202-404-3322

Copyright © Naval Research Laboratory

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

Nanoscale worms provide new route to nano-necklace structures March 29th, 2015

Solving molybdenum disulfide's 'thin' problem: Research team increases material's light emission by twelve times March 29th, 2015

A first glimpse inside a macroscopic quantum state March 28th, 2015

DFG to Establish One Clinical Research Unit and Five Research Units: New Projects to Investigate Complications in Pregnancy, Particle Physics, Nanoparticles, Implants and Transport Planning / Approximately 13 Million Euros in Funding for an Initial Three-Year Period March 28th, 2015

State-of-the-art online system unveiled to pinpoint metrology software accuracy March 27th, 2015

Physics

A first glimpse inside a macroscopic quantum state March 28th, 2015

Using magnetic fields to understand high-temperature superconductivity: Los Alamos explores experimental path to potential 'next theory of superconductivity' March 27th, 2015

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

Laboratories

Using magnetic fields to understand high-temperature superconductivity: Los Alamos explores experimental path to potential 'next theory of superconductivity' March 27th, 2015

Govt.-Legislation/Regulation/Funding/Policy

Nanoscale worms provide new route to nano-necklace structures March 29th, 2015

UT Dallas engineers twist nanofibers to create structures tougher than bulletproof vests March 27th, 2015

Novel nanoparticle therapy promotes wound healing March 27th, 2015

Designer's toolkit for dynamic DNA nanomachines: Arm-waving nanorobot signals new flexibility in DNA origami March 27th, 2015

Discoveries

Nanoscale worms provide new route to nano-necklace structures March 29th, 2015

Solving molybdenum disulfide's 'thin' problem: Research team increases material's light emission by twelve times March 29th, 2015

A first glimpse inside a macroscopic quantum state March 28th, 2015

Designer's toolkit for dynamic DNA nanomachines: Arm-waving nanorobot signals new flexibility in DNA origami March 27th, 2015

Announcements

Nanoscale worms provide new route to nano-necklace structures March 29th, 2015

Solving molybdenum disulfide's 'thin' problem: Research team increases material's light emission by twelve times March 29th, 2015

A first glimpse inside a macroscopic quantum state March 28th, 2015

DFG to Establish One Clinical Research Unit and Five Research Units: New Projects to Investigate Complications in Pregnancy, Particle Physics, Nanoparticles, Implants and Transport Planning / Approximately 13 Million Euros in Funding for an Initial Three-Year Period March 28th, 2015

Interviews/Book Reviews/Essays/Reports/Podcasts/Journals/White papers

Nanoscale worms provide new route to nano-necklace structures March 29th, 2015

Solving molybdenum disulfide's 'thin' problem: Research team increases material's light emission by twelve times March 29th, 2015

A first glimpse inside a macroscopic quantum state March 28th, 2015

Novel nanoparticle therapy promotes wound healing March 27th, 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

Research partnerships

SUNY Poly & M+W Make Major Announcement: Major Expansion To Include M+W Owned Gehrlicher Solar America Corporation That Will Create up to 400 Jobs to Develop Solar Power Plants at SUNY Poly Sites Across New York State March 26th, 2015

ORNL-led team demonstrates desalination with nanoporous graphene membrane March 25th, 2015

New kind of 'tandem' solar cell developed: Researchers combine 2 types of photovoltaic material to make a cell that harnesses more sunlight March 24th, 2015

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