Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Princeton scientist makes a leap in quantum computing

08.02.2010
A major hurdle in the ambitious quest to design and construct a radically new kind of quantum computer has been finding a way to manipulate the single electrons that very likely will constitute the new machines' processing components or "qubits."

Princeton University's Jason Petta has discovered how to do just that -- demonstrating a method that alters the properties of a lone electron without disturbing the trillions of electrons in its immediate surroundings. The feat is essential to the development of future varieties of superfast computers with near-limitless capacities for data.

Petta, an assistant professor of physics, has fashioned a new method of trapping one or two electrons in microscopic corrals created by applying voltages to minuscule electrodes. Writing in the Feb. 5 edition of Science, he describes how electrons trapped in these corrals form "spin qubits," quantum versions of classic computer information units known as bits. Other authors on the paper include Art Gossard and Hong Lu at the University of California-Santa Barbara.

Previous experiments used a technique in which electrons in a sample were exposed to microwave radiation. However, because it affected all the electrons uniformly, the technique could not be used to manipulate single electrons in spin qubits. It also was slow. Petta's method not only achieves control of single electrons, but it does so extremely rapidly -- in one-billionth of a second.

"If you can take a small enough object like a single electron and isolate it well enough from external perturbations, then it will behave quantum mechanically for a long period of time," said Petta. "All we want is for the electron to just sit there and do what we tell it to do. But the outside world is sort of poking at it, and that process of the outside world poking at it causes it to lose its quantum mechanical nature."

When the electrons in Petta's experiment are in what he calls their quantum state, they are "coherent," following rules that are radically different from the world seen by the naked eye. Living for fractions of a second in the realm of quantum physics before they are rattled by external forces, the electrons obey a unique set of physical laws that govern the behavior of ultra-small objects.

Scientists like Petta are working in a field known as quantum control where they are learning how to manipulate materials under the influence of quantum mechanics so they can exploit those properties to power advanced technologies like quantum computing. Quantum computers will be designed to take advantage of these characteristics to enrich their capacities in many ways.

In addition to electrical charge, electrons possess rotational properties. In the quantum world, objects can turn in ways that are at odds with common experience. The Austrian theoretical physicist Wolfgang Pauli, who won the Nobel Prize in Physics in 1945, proposed that an electron in a quantum state can assume one of two states -- "spin-up" or "spin-down." It can be imagined as behaving like a tiny bar magnet with spin-up corresponding to the north pole pointing up and spin-down corresponding to the north pole pointing down.

An electron in a quantum state can simultaneously be partially in the spin-up state and partially in the spin-down state or anywhere in between, a quantum mechanical property called "superposition of states." A qubit based on the spin of an electron could have nearly limitless potential because it can be neither strictly on nor strictly off.

New designs could take advantage of a rich set of possibilities offered by harnessing this property to enhance computing power. In the past decade, theorists and mathematicians have designed algorithms that exploit this mysterious superposition to perform intricate calculations at speeds unmatched by supercomputers today.

Petta's work is using electron spin to advantage.

"In the quest to build a quantum computer with electron spin qubits, nuclear spins are typically a nuisance," said Guido Burkard, a theoretical physicist at the University of Konstanz in Germany. "Petta and coworkers demonstrate a new method that utilizes the nuclear spins for performing fast quantum operations. For solid-state quantum computing, their result is a big step forward."

Petta's spin qubits, which he envisions as the core of future quantum logic elements, are cooled to temperatures near absolute zero and trapped in two tiny corrals known as quantum wells on the surface of a high-purity, gallium arsenide chip. The depth of each well is controlled by varying the voltage on tiny electrodes or gates. Like a juggler tossing two balls between his hands, Petta can move the electrons from one well to the other by selectively toggling the gate voltages.

Prior to this experiment, it was not clear how experimenters could manipulate the spin of one electron without disturbing the spin of another in a closely packed space, according to Phuan Ong, the Eugene Higgins Professor of Physics at Princeton and director of the Princeton Center for Complex Materials.

Other experts agree.

"They have managed to create a very exotic transient condition, in which the spin state of a pair of electrons is in that moment entangled with an almost macroscopic degree of freedom," said David DiVencenzo, a research staff member at the IBM Thomas J. Watson Research Center in Yorktown Heights, N.Y.

Petta's research also is part of the fledgling field of "spintronics" in which scientists are studying how to use an electron's spin to create new types of electronic devices. Most electrical devices today operate on the basis of another key property of the electron -- its charge.

There are many more challenges to face, Petta said.

"Our approach is really to look at the building blocks of the system, to think deeply about what the limitations are and what we can do to overcome them," Petta said. "But we are still at the level of just manipulating one or two quantum bits, and you really need hundreds to do something useful."

As excited as he is about present progress, long-term applications are still years away. "It's a one-day-at-a-time approach," Petta said.

Kitta MacPherson | EurekAlert!
Further information:
http://www.princeton.edu

More articles from Information Technology:

nachricht New 3-D display takes the eye fatigue out of virtual reality
22.06.2017 | The Optical Society

nachricht Modeling the brain with 'Lego bricks'
19.06.2017 | University of Luxembourg

All articles from Information Technology >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Climate satellite: Tracking methane with robust laser technology

Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.

Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...

Im Focus: How protons move through a fuel cell

Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.

As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...

Im Focus: A unique data centre for cosmological simulations

Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.

With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...

Im Focus: Scientists develop molecular thermometer for contactless measurement using infrared light

Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine

Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...

Im Focus: Optoelectronic Inline Measurement – Accurate to the Nanometer

Germany counts high-precision manufacturing processes among its advantages as a location. It’s not just the aerospace and automotive industries that require almost waste-free, high-precision manufacturing to provide an efficient way of testing the shape and orientation tolerances of products. Since current inline measurement technology not yet provides the required accuracy, the Fraunhofer Institute for Laser Technology ILT is collaborating with four renowned industry partners in the INSPIRE project to develop inline sensors with a new accuracy class. Funded by the German Federal Ministry of Education and Research (BMBF), the project is scheduled to run until the end of 2019.

New Manufacturing Technologies for New Products

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Plants are networkers

19.06.2017 | Event News

Digital Survival Training for Executives

13.06.2017 | Event News

Global Learning Council Summit 2017

13.06.2017 | Event News

 
Latest News

A new technique isolates neuronal activity during memory consolidation

22.06.2017 | Life Sciences

Plant inspiration could lead to flexible electronics

22.06.2017 | Materials Sciences

A rhodium-based catalyst for making organosilicon using less precious metal

22.06.2017 | Materials Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>