Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Fast Quantum Computer Building Block Created

22.08.2008
The fastest quantum computer bit that exploits the main advantage of the qubit over the conventional bit has been demonstrated by researchers at University of Michigan, U.S. Naval Research Laboratory and the University of California at San Diego.

The fastest quantum computer bit that exploits the main advantage of the qubit over the conventional bit has been demonstrated by researchers at University of Michigan, U.S. Naval Research Laboratory and the University of California at San Diego.

The scientists used lasers to create an initialized quantum state of this solid-state qubit at rates of about a gigahertz, or a billion times per second. They can also use lasers to achieve fundamental steps toward programming it.

A conventional bit can be a 0 or a 1. A quantum bit, or qubit, can be both at the same time. Until now, scientists couldn't stabilize that duality.

Physics professor Duncan Steel, doctoral student Xiaodong Xu and their colleagues used lasers to coherently, or stably, trap the spin of one electron confined in a single semiconductor quantum dot. A quantum dot is like a transistor in a conventional computer.

The scientists trapped the spin in a dark state in which they can arbitrarily adjust the amount of 0 and 1 the qubit represents. They call this state "dark" because it does not absorb light. Therefore, light does not cause loss of coherence between the two states. In other words, the light does not destabilize the qubit. A paper on these findings will be published in Nature Physics and is available early in the online edition.

"We are the first to show that you can do this to a single electron in a self-assembled quantum dot," Steel said. "If you're going to do quantum computing, you have to be able to work with one electron at a time."

Spin is an intrinsic property of the electron that isn't a real rotation. Steel compares it to the magnetic poles. Electrons are said to have spin up or down. In quantum computing, the up and down directions represent the 0s and 1s of conventional computing.

Steel's approach to developing a quantum computer is to use ultrafast lasers to manipulate arrays of semiconductor quantum dots, each containing one electron. Quantum logic gates are formed by quantum mechanical interactions between the dots.

Previously in Steel's lab, researchers have used a laser to produce an electron in a state representative of a 1 or a 0 and a small amount of the other state. Now, using two laser frequencies, they have trapped it as a 0 and a 1 at the same time, and they can adjust the amount of each.

Because the electron is trapped in a dark state, applied light can't destroy the coherence. Energy from light can flip the spin of electrons, or quantum bits, which would jumble any information being stored in the bit.

"This dark state is a place where information can be stored without any error," Steel said.

Because of their ability to represent multiple states simultaneously, quantum computers could theoretically factor numbers dramatically faster and with smaller computers than conventional computers. For this reason, they could vastly improve computer security.

"The National Security Agency has said that based on our present technology, we have about a 20-year window of security," Steel said. "That means if we sent up a satellite today, it would take somebody about 20 years to crack the code. Quantum computers will let you develop a code that would be impossible to crack with a conventional computer."

Physicists achieved this by using two continuous wave lasers.

Steel is the Robert J. Hiller Professor of Engineering in the Department of Electrical Engineering and Computer Science as well as a professor in the Physics Department. Xu, a doctoral student in Physics, is first author of the Nature Physics paper. Steel is also an author. The principal investigators include Dan Gammon of the Naval Research Laboratory and physics professor Lu Jeu Sham at the University of California at San Diego.

The paper is called "Coherent Population Trapping of an Electron Spin in a Single Negatively Charged Quantum Dot." It is available online at http://www.nature.com/nphys/journal/vaop/ncurrent/full/nphys1054.html.

For more information:
Duncan Steel: http://www.ns.umich.edu/htdocs/public/experts/ExpDisplay.php?ExpID=1226
Michigan Engineering:
The University of Michigan College of Engineering is ranked among the top engineering schools in the country. At more than $130 million annually, its engineering research budget is one of the largest of any public university. Michigan Engineering is home to 11 academic departments and a National Science Foundation Engineering Research Center. The college plays a leading role in the Michigan Memorial Phoenix Energy Institute and hosts the world class Lurie Nanofabrication Facility. Find out more at http://www.engin.umich.edu/.

Nicole Casal Moore | Newswise Science News
Further information:
http://www.umich.edu
http://www.ns.umich.edu/htdocs/public/experts/ExpDisplay.php?ExpID=1226
http://www.nature.com/nphys/journal/vaop/ncurrent/full/nphys1054.html.

More articles from Information Technology:

nachricht Cloud technology: Dynamic certificates make cloud service providers more secure
15.01.2018 | Technische Universität München

nachricht New discovery could improve brain-like memory and computing
10.01.2018 | University of Minnesota

All articles from Information Technology >>>

The most recent press releases about innovation >>>

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

Im Focus: Artificial agent designs quantum experiments

On the way to an intelligent laboratory, physicists from Innsbruck and Vienna present an artificial agent that autonomously designs quantum experiments. In initial experiments, the system has independently (re)discovered experimental techniques that are nowadays standard in modern quantum optical laboratories. This shows how machines could play a more creative role in research in the future.

We carry smartphones in our pockets, the streets are dotted with semi-autonomous cars, but in the research laboratory experiments are still being designed by...

Im Focus: Scientists decipher key principle behind reaction of metalloenzymes

So-called pre-distorted states accelerate photochemical reactions too

What enables electrons to be transferred swiftly, for example during photosynthesis? An interdisciplinary team of researchers has worked out the details of how...

Im Focus: The first precise measurement of a single molecule's effective charge

For the first time, scientists have precisely measured the effective electrical charge of a single molecule in solution. This fundamental insight of an SNSF Professor could also pave the way for future medical diagnostics.

Electrical charge is one of the key properties that allows molecules to interact. Life itself depends on this phenomenon: many biological processes involve...

Im Focus: Paradigm shift in Paris: Encouraging an holistic view of laser machining

At the JEC World Composite Show in Paris in March 2018, the Fraunhofer Institute for Laser Technology ILT will be focusing on the latest trends and innovations in laser machining of composites. Among other things, researchers at the booth shared with the Aachen Center for Integrative Lightweight Production (AZL) will demonstrate how lasers can be used for joining, structuring, cutting and drilling composite materials.

No other industry has attracted as much public attention to composite materials as the automotive industry, which along with the aerospace industry is a driver...

Im Focus: Room-temperature multiferroic thin films and their properties

Scientists at Tokyo Institute of Technology (Tokyo Tech) and Tohoku University have developed high-quality GFO epitaxial films and systematically investigated their ferroelectric and ferromagnetic properties. They also demonstrated the room-temperature magnetocapacitance effects of these GFO thin films.

Multiferroic materials show magnetically driven ferroelectricity. They are attracting increasing attention because of their fascinating properties such as...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

10th International Symposium: “Advanced Battery Power – Kraftwerk Batterie” Münster, 10-11 April 2018

08.01.2018 | Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

 
Latest News

Thanks for the memory: NIST takes a deep look at memristors

22.01.2018 | Materials Sciences

Radioactivity from oil and gas wastewater persists in Pennsylvania stream sediments

22.01.2018 | Earth Sciences

Saarland University bioinformaticians compute gene sequences inherited from each parent

22.01.2018 | Life Sciences

VideoLinks Wissenschaft & Forschung
Overview of more VideoLinks >>>