Fast quantum computer building block created
August 20, 2008(PhysOrg.com) -- 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.
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. … hys1054.html .
Provided by University of Michigan
-
Lab team develops capability for atomistic simulations
Jan 27, 2012 |
5 / 5 (3) |
0
-
The world's smallest magnetic data storage unit
Jan 12, 2012 |
4.7 / 5 (21) |
24
-
Rice's 'quantum critical' theory gets experimental boost
Jan 11, 2012 |
4.1 / 5 (14) |
2
-
Researchers prepare cheap quantum dot solar paint
Dec 16, 2011 |
4.5 / 5 (22) |
15
-
Discovery of a 'dark state' could increase maximum theoretical efficiency of solar cells from 31 to 44 percent
Dec 15, 2011 |
4.8 / 5 (23) |
12
-
Engineers build first sub-10-nm carbon nanotube transistor
Feb 01, 2012 |
4.9 / 5 (33) |
30
-
Something old, something new: Evolution and the structural divergence of duplicate genes
Jan 31, 2012 |
4.6 / 5 (7) |
1
-
The hidden nanoworld of ice crystals: Revealing the dynamic behavior of quasi-liquid layers
Jan 30, 2012 |
5 / 5 (4) |
1
-
Stock market network reveals investor clustering
Jan 27, 2012 |
3.9 / 5 (23) |
8
-
Of microchemistry and molecules: Electronic microfluidic device synthesizes biocompatible probes
Jan 26, 2012 |
5 / 5 (2) |
0
-
Can Plasma Be Solid
2 hours ago
-
What is delta Δ ?
3 hours ago
-
Need some help understanding HertzĀKnudsen formula
3 hours ago
-
Anatomy of Fat man: implosion-critical bomb
5 hours ago
-
what makes two sounds similar???
6 hours ago
-
What would happen when a jet travelling at Mach 10 experiences engine failure
12 hours ago
- More from Physics Forums - General Physics
More news stories
Explained: Sigma
It's a question that arises with virtually every major new finding in science or medicine: What makes a result reliable enough to be taken seriously? The answer has to do with statistical significance -- but ...
Feb 09, 2012 |
5 / 5 (20) |
76
Quantum physicist explains $100K offer for proof scaled-up quantum computing is impossible
(PhysOrg.com) -- MIT researcher Scott Aaronson has certainly riled the physics community with his offer this past Friday, of $100,000 to anyone who can prove that scaled-up quantum computing is impossible. ...
Diamond light, brighter than the sun
Its the size of five football pitches and generates light 10 billion times brighter than the sun. As the Diamond Light Source celebrates its tenth anniversary this year, Penny Bailey visits one of the ...
Feb 07, 2012 |
4.1 / 5 (10) |
18
|
Physicists 'record' magnetic breakthrough
An international team of scientists has demonstrated a revolutionary new way of magnetic recording which will allow information to be processed hundreds of times faster than by current hard drive technology.
Feb 07, 2012 |
4.6 / 5 (43) |
15
|
Hints of the Higgs - papers are submitted
Back in December 2011, the ATLAS and CMS experiments at CERN presented some exciting results that provided tantalising hints of the Higgs boson.
Feb 08, 2012 |
4.3 / 5 (8) |
10
Scientists discover molecular secrets of 2,000-year-old Chinese herbal remedy
For roughly two thousand years, Chinese herbalists have treated Malaria using a root extract, commonly known as Chang Shan, from a type of hydrangea that grows in Tibet and Nepal. More recent studies suggest that halofuginone, ...
New method to examine batteries -- MRI from the inside
There is an ever-increasing need for advanced batteries for portable electronics, such as phones, cameras, and music players, but also to power electric vehicles and to facilitate the distribution and storage of energy derived ...
A mitosis mystery solved: How chromosomes align perfectly in a dividing cell
Although the process of mitotic cell division has been studied intensely for more than 50 years, Whitehead Institute researchers have only now solved the mystery of how cells correctly align their chromosomes during symmetric ...
Google might launch Drive for cloud storage soon
(PhysOrg.com) -- Google's next big move, according to the Wall Street Journal, is a cloud storage service called Drive. Hardly first to the plate, Google is simply catching up to introducing its cloud reposi ...
Lab study raises questions over nano-particle impact
Tests involving chickens have raised questions about the impact on health from engineered nano-particles, the ultra-fine grains commonly used in drugs and processed foods, scientists said on Sunday.
Overeating may double risk of memory loss
New research suggests that consuming between 2,100 and 6,000 calories per day may double the risk of memory loss, or mild cognitive impairment (MCI), among people age 70 and older. The study was released today and will be ...
Aug 20, 2008
Rank: not rated yet
Aug 20, 2008
Rank: not rated yet
Anyway, This is still experimentation. Has anyone tried making a small memory proto-type??? Any real world usage of this? Have they stored a character or two with this technique?
Pick a technique and try applying it. Sure the technique used may change but maybe we will learn something.
Aug 21, 2008
Rank: 5 / 5 (1)
The purpose of bits and qubits is to store information they have no associated speed.
No, they can use lasers to program it.
Huh? Stabilize what duality? They could set qubits to any state they wanted.
Coherently does not mean stably, and you cannot trap spin, you can set spin.
A quantum dot a completely different thing then a transistor in conventional computer.
Dark things are dark because they DO absorb light. Also if it does not absorb light how can they set it with lasers?
Not true, just today I read about quantum computing with strings of ions in ion traps.
It isn't real magnetic poles either.
And so on...
Aug 21, 2008
Rank: not rated yet
publication in the first quarter of 2009. Interested parties, do feel free to check out the paper submission details at:
http://www.worlds...608).pdf
Thanks and Regards:-)