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 CubeSats prove their worth for scientific missions
17.04.2019 | American Physical Society

nachricht Largest, fastest array of microscopic 'traffic cops' for optical communications
12.04.2019 | University of California - Berkeley

All articles from Information Technology >>>

The most recent press releases about innovation >>>

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

Im Focus: Explosion on Jupiter-sized star 10 times more powerful than ever seen on our sun

A stellar flare 10 times more powerful than anything seen on our sun has burst from an ultracool star almost the same size as Jupiter

  • Coolest and smallest star to produce a superflare found
  • Star is a tenth of the radius of our Sun
  • Researchers led by University of Warwick could only see...

Im Focus: Quantum simulation more stable than expected

A localization phenomenon boosts the accuracy of solving quantum many-body problems with quantum computers which are otherwise challenging for conventional computers. This brings such digital quantum simulation within reach on quantum devices available today.

Quantum computers promise to solve certain computational problems exponentially faster than any classical machine. “A particularly promising application is the...

Im Focus: Largest, fastest array of microscopic 'traffic cops' for optical communications

The technology could revolutionize how information travels through data centers and artificial intelligence networks

Engineers at the University of California, Berkeley have built a new photonic switch that can control the direction of light passing through optical fibers...

Im Focus: A long-distance relationship in femtoseconds

Physicists observe how electron-hole pairs drift apart at ultrafast speed, but still remain strongly bound.

Modern electronics relies on ultrafast charge motion on ever shorter length scales. Physicists from Regensburg and Gothenburg have now succeeded in resolving a...

Im Focus: Researchers 3D print metamaterials with novel optical properties

Engineers create novel optical devices, including a moth eye-inspired omnidirectional microwave antenna

A team of engineers at Tufts University has developed a series of 3D printed metamaterials with unique microwave or optical properties that go beyond what is...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Revered mathematicians and computer scientists converge with 200 young researchers in Heidelberg!

17.04.2019 | Event News

First dust conference in the Central Asian part of the earth’s dust belt

15.04.2019 | Event News

Fraunhofer FHR at the IEEE Radar Conference 2019 in Boston, USA

09.04.2019 | Event News

 
Latest News

New automated biological-sample analysis systems to accelerate disease detection

18.04.2019 | Life Sciences

Explosion on Jupiter-sized star 10 times more powerful than ever seen on our sun

18.04.2019 | Physics and Astronomy

New eDNA technology used to quickly assess coral reefs

18.04.2019 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>