Nanotechnology Now

Our NanoNews Digest Sponsors

Heifer International

Wikipedia Affiliate Button

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

ICN2 researchers compute unprecedented values for spin lifetime anisotropy in graphene November 17th, 2017

Math gets real in strong, lightweight structures: Rice University researchers use 3-D printers to turn century-old theory into complex schwarzites November 16th, 2017

The stacked color sensor: True colors meet minimization November 16th, 2017

Nanometrics to Participate in the 6th Annual NYC Investor Summit 2017 November 16th, 2017

Physics

Inorganic-organic halide perovskites for new photovoltaic technology November 6th, 2017

Halas wins American Physical Society's Lilienfeld Prize: Rice University nanoscientist honored for pioneering research in plasmonics October 23rd, 2017

A step closer to understanding quantum mechanics: Swansea University’s physicists develop a new quantum simulation protocol October 22nd, 2017

Laboratories

Ames Laboratory, UConn discover superconductor with bounce October 25th, 2017

Nanotube fiber antennas as capable as copper: Rice University researchers show their flexible fibers work well but weigh much less October 23rd, 2017

Govt.-Legislation/Regulation/Funding/Policy

EC Project Aims at Creating and Commercializing Cyber-Physical-System Solutions November 14th, 2017

Nanobiotix presented new clinical and pre-clinical data confirming NBTXR3’s significant potential role in Immuno-Oncology at SITC Annual Meeting November 14th, 2017

Leti Joins DARPA-Funded Project to Develop Implantable Device for Restoring Vision November 9th, 2017

Nanoshells could deliver more chemo with fewer side effects: In vitro study verifies method for remotely triggering release of cancer drugs November 8th, 2017

Discoveries

ICN2 researchers compute unprecedented values for spin lifetime anisotropy in graphene November 17th, 2017

Math gets real in strong, lightweight structures: Rice University researchers use 3-D printers to turn century-old theory into complex schwarzites November 16th, 2017

The stacked color sensor: True colors meet minimization November 16th, 2017

Counterfeits and product piracy can be prevented by security features, such as printed 3-D microstructures: Forgeries and product piracy are detrimental to society and industry -- 3-D microstructures can increase security -- KIT researchers develop innovative fluorescent 3-D stru November 15th, 2017

Announcements

ICN2 researchers compute unprecedented values for spin lifetime anisotropy in graphene November 17th, 2017

Math gets real in strong, lightweight structures: Rice University researchers use 3-D printers to turn century-old theory into complex schwarzites November 16th, 2017

The stacked color sensor: True colors meet minimization November 16th, 2017

Nanometrics to Participate in the 6th Annual NYC Investor Summit 2017 November 16th, 2017

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

ICN2 researchers compute unprecedented values for spin lifetime anisotropy in graphene November 17th, 2017

Math gets real in strong, lightweight structures: Rice University researchers use 3-D printers to turn century-old theory into complex schwarzites November 16th, 2017

The stacked color sensor: True colors meet minimization November 16th, 2017

Counterfeits and product piracy can be prevented by security features, such as printed 3-D microstructures: Forgeries and product piracy are detrimental to society and industry -- 3-D microstructures can increase security -- KIT researchers develop innovative fluorescent 3-D stru November 15th, 2017

Quantum Dots/Rods

Quantum communications bend to our needs: By changing the wavelengths of entangled photons to those used in telecommunications, researchers see quantum technology take a major leap forward September 28th, 2017

Band Gaps, Made to Order: Engineers create atomically thin superlattice materials with precision September 26th, 2017

New approach on research and design for CQD catalysts in World Scientific NANO August 2nd, 2017

Coupling a nano-trumpet with a quantum dot enables precise position determination July 14th, 2017

Research partnerships

EC Project Aims at Creating and Commercializing Cyber-Physical-System Solutions November 14th, 2017

Leti Joins DARPA-Funded Project to Develop Implantable Device for Restoring Vision November 9th, 2017

Nanoshells could deliver more chemo with fewer side effects: In vitro study verifies method for remotely triggering release of cancer drugs November 8th, 2017

Ames Laboratory, UConn discover superconductor with bounce October 25th, 2017

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