Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Scientists find flaw in quantum dot construction

11.02.2005


Nanoscientists dream of developing a quantum computer, a device the size of a grain of sand that could be faster and more powerful than today’s PCs. They’ve identified tiny artificial atoms – called "quantum dots" – as the most likely materials to build these machines, but have been puzzled by the dots’ unpredictable behavior at the nanoscale.



Now a team of Ohio University physicists thinks it’s found the problem – and has proposed a blueprint for building a better quantum dot. The researchers, who published their findings in this week’s issue of Physical Review Letters, argue that defects formed during creation of the quantum dots operate as a barrier to scientific experimentation.

Experimental scientists in Germany had blasted the quantum dots with light to create the quantum mechanical state needed to run a quantum computer. But they couldn’t consistently control that state, explained Sergio Ulloa, an Ohio University professor of physics and astronomy. Jose Villas-Boas, a postdoctoral fellow at Ohio University, Ulloa and Associate Professor Alexander Govorov developed theoretical models to learn what went wrong.


The problem, they argued, happens during the creation of the type of quantum dots under study. Using a molecular beam epitaxy chamber, scientists spray paint a surface with atoms under high temperatures, creating an atomic coating. As more layers are added, the quantum dots bead up on the surface like droplets of water, Ulloa said. But a fine residue left behind on the surface that Ulloa calls the "wetting layer" can cause problems during experiments. When experimental scientists blasted the quantum dots with a beam of light in previous studies, the wetting layer caused interference, instead of allowing the light to enter the dot and trigger the quantum state, he explained.

The study suggests that scientists could tweak the process by re-focusing the beam of light or changing the duration of the light pulses to negate the effects of the wetting layer, Villas-Boas said. One experimental physicist already has used the theoretical finding to successfully manipulate a quantum dot in the lab, he added. "Now that they know the problem, they realize there are a few ways to avoid it," Villas-Boas said.

The new finding ultimately could lead to the creation of a better quantum dot and can help scientists understand more about quantum states, Ulloa added. "It’s one more step towards the holy grail of finding a better quantum bit, which hopefully will lead to a quantum computer," he said.

Nanoscientists are creating quantum dots in many different ways, Ulloa noted, for use in various applications. The self-assembled type under study could be used in optical electronics and quantum computers. Other types, such as dots grown in a solution, might be used for solar energy applications.

The study also will help the Ohio University team better understand how to control the spin of electrons – a property that could be the underlying mechanism behind faster, more efficient future electronic devices, he added.

Andrea Gibson | EurekAlert!
Further information:
http://www.ohio.edu

More articles from Physics and Astronomy:

nachricht Studying fundamental particles in materials
17.01.2017 | Max-Planck-Institut für Struktur und Dynamik der Materie

nachricht Seeing the quantum future... literally
16.01.2017 | University of Sydney

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: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

Im Focus: How to inflate a hardened concrete shell with a weight of 80 t

At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).

Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...

Im Focus: Bacterial Pac Man molecule snaps at sugar

Many pathogens use certain sugar compounds from their host to help conceal themselves against the immune system. Scientists at the University of Bonn have now, in cooperation with researchers at the University of York in the United Kingdom, analyzed the dynamics of a bacterial molecule that is involved in this process. They demonstrate that the protein grabs onto the sugar molecule with a Pac Man-like chewing motion and holds it until it can be used. Their results could help design therapeutics that could make the protein poorer at grabbing and holding and hence compromise the pathogen in the host. The study has now been published in “Biophysical Journal”.

The cells of the mouth, nose and intestinal mucosa produce large quantities of a chemical called sialic acid. Many bacteria possess a special transport system...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

Nothing will happen without batteries making it happen!

05.01.2017 | Event News

 
Latest News

Water - as the underlying driver of the Earth’s carbon cycle

17.01.2017 | Earth Sciences

Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

17.01.2017 | Materials Sciences

Smart homes will “LISTEN” to your voice

17.01.2017 | Architecture and Construction

VideoLinks
B2B-VideoLinks
More VideoLinks >>>