Featured Research

from universities, journals, and other organizations

Fast Quantum Computer Building Block Created

Date:
August 25, 2008
Source:
University of Michigan
Summary:
The fastest quantum computer bit that exploits the main advantage of the qubit over the conventional bit has been demonstrated. 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.

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.


Story Source:

The above story is based on materials provided by University of Michigan. Note: Materials may be edited for content and length.


Journal Reference:

  1. Xu et al. Coherent population trapping of an electron spin in a single negatively charged quantum dot. Nature Physics, 2008; DOI: 10.1038/nphys1054

Cite This Page:

University of Michigan. "Fast Quantum Computer Building Block Created." ScienceDaily. ScienceDaily, 25 August 2008. <www.sciencedaily.com/releases/2008/08/080820162956.htm>.
University of Michigan. (2008, August 25). Fast Quantum Computer Building Block Created. ScienceDaily. Retrieved September 23, 2014 from www.sciencedaily.com/releases/2008/08/080820162956.htm
University of Michigan. "Fast Quantum Computer Building Block Created." ScienceDaily. www.sciencedaily.com/releases/2008/08/080820162956.htm (accessed September 23, 2014).

Share This



More Computers & Math News

Tuesday, September 23, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Company Copies Keys From Photos

Company Copies Keys From Photos

Newsy (Sep. 22, 2014) A new company allows customers to make copies of keys by simply uploading a couple of photos. But could it also be great for thieves? Video provided by Newsy
Powered by NewsLook.com
Cat Lovers Flock to Los Angeles

Cat Lovers Flock to Los Angeles

AFP (Sep. 22, 2014) The best funny internet cat videos are honoured at LA's Feline Film Festival. Duration: 00:56 Video provided by AFP
Powered by NewsLook.com
Raw: SpaceX Rocket Carries 3-D Printer to Space

Raw: SpaceX Rocket Carries 3-D Printer to Space

AP (Sep. 22, 2014) A SpaceX Rocket launched from Cape Canaveral, carrying a custom-built 3-D printer into space. NASA envisions astronauts one day using the printer to make their own spare parts. (Sept. 22) Video provided by AP
Powered by NewsLook.com
What This MIT Sensor Could Mean For The Future Of Robotics

What This MIT Sensor Could Mean For The Future Of Robotics

Newsy (Sep. 20, 2014) MIT researchers developed a light-based sensor that gives robots 100 times the sensitivity of a human finger, allowing for "unprecedented dexterity." Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Space & Time

Matter & Energy

Computers & Math

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins