Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Physicists measure individual electrons in real time

22.05.2003


Ultracold experiment opens door for basic studies in quantum computing


A ring-shaped electric field runs round the tips of the five (light-colored) gold wires, creating a central island where some 80 electrons are isolated from electrons in the rest of the structure.



Physicists at Rice University have completed the first real-time measurement of individual electrons, creating an experimental method that for the first time allows scientists to probe the dynamic interactions between the smallest atomic particles.

The research, which appears in the May 22 issue of the journal Nature, is important for researchers developing quantum computers, a revolutionary type of computer that is orders of magnitude more powerful than any computer ever built.


To date, computers have used the binary bit -- represented by either a one or zero -- as their fundamental unit of information. In a quantum computer, the fundamental unit is a quantum bit, or qubit. Because qubits can have more than two states, calculations that would take a supercomputer years to finish will take a quantum computer mere seconds.

Due to the complexities of quantum dynamics, electrons can serve as qubits. They can exist in "up" and "down" states -- single points that are analogous to the ones and zeroes in classical computers -- or in "superposition" states, which are not single points but patterns of probability that exist in several places at once.

The Rice experiments took place in an ultracold chamber chilled to temperatures below those found in deep space. There, for the first time, scientists were able to observe individual electrons as they moved onto and off of a nanoscopic piece of a semiconductor known as a quantum dot.

"Since no one has measured single electron dynamics before, the door is wide open for new investigations," said lead researcher Alex Rimberg, assistant professor of physics and astronomy and of electrical and computer engineering. "These include studies of the interactions between individual electrons, as well as the quantum phenomena that engineers must understand if they ever want to build a working quantum computer."

Rimberg’s group, which includes graduate students Wei Lu and Zhongqing Ji, built its quantum dot using an ultra-thin layer of semiconducting gallium arsenide. Using gold wiring, they created a ring-shaped electrostatic field, isolating a small pool of electrons on a 300-nanometer piece of gallium arsenide inside the ring. An extremely sensitive charge-sensing device called a radio-frequency single-electron transistor (RF-SET) was placed next to the pool. Operating in a fashion akin to an AM radio, the RF-SET registered changes in the amplitude modulation of radio waves reflected by the pool. The modulations changed as electrons entered and left the pool.

"We were able to tune this system so that our pool was equally happy with, say, 79 or 80 electrons," said Rimberg. "By raising the power of the electric field, we raised the barrier around the pool, making it very difficult for electrons to enter or leave the pool. That allowed us to slow down the electron motion enough to measure the coming and going of individual electrons."

Though physicists have used SET technology to measure the movement of single electrons for several years, the response time in previous experiments was about 1,000 times slower. Rimberg likened the difference to a system that could detect commuters moving in and out of Grand Central Station.

"Before, you could say that individual people were coming and going from the station, and you knew the average number of people in the station, but each measurement took several minutes, so you could never say precisely when a particular individual arrived or left," said Rimberg.

Like commuters jockeying for position on a railway platform, electrons also interact with one another in close proximity. Rimberg hopes physicists can use the ultracold RF-SET system to test competing theories that explain how electrons influence each another.


The research was sponsored by the National Science Foundation, the Army Research Office and the Robert A. Welch Foundation.


Jade Boyd | EurekAlert!
Further information:
http://chico.rice.edu/

More articles from Physics and Astronomy:

nachricht Computer model predicts how fracturing metallic glass releases energy at the atomic level
20.07.2018 | American Institute of Physics

nachricht What happens when we heat the atomic lattice of a magnet all of a sudden?
18.07.2018 | Forschungsverbund Berlin

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: Future electronic components to be printed like newspapers

A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.

The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...

Im Focus: First evidence on the source of extragalactic particles

For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.

To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...

Im Focus: Magnetic vortices: Two independent magnetic skyrmion phases discovered in a single material

For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.

Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...

Im Focus: Breaking the bond: To take part or not?

Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.

A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...

Im Focus: New 2D Spectroscopy Methods

Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.

"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Leading experts in Diabetes, Metabolism and Biomedical Engineering discuss Precision Medicine

13.07.2018 | Event News

Conference on Laser Polishing – LaP: Fine Tuning for Surfaces

12.07.2018 | Event News

11th European Wood-based Panel Symposium 2018: Meeting point for the wood-based materials industry

03.07.2018 | Event News

 
Latest News

A smart safe rechargeable zinc ion battery based on sol-gel transition electrolytes

20.07.2018 | Power and Electrical Engineering

Reversing cause and effect is no trouble for quantum computers

20.07.2018 | Information Technology

Princeton-UPenn research team finds physics treasure hidden in a wallpaper pattern

20.07.2018 | Materials Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>