Fast quantum computer building block createdAugust 21, 2008ANN ARBOR, Mich.---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. University of Michigan | |||||||||||||||||||||
|
Related Quantum Computer Current Events and Quantum Computer News Articles Quantum computers could excel in modeling chemical reactions Quantum computers would likely outperform conventional computers in simulating chemical reactions involving more than four atoms, according to scientists at Harvard University, the Massachusetts Institute of Technology, and Haverford College. News Bits About Qubits: Scientists Store and Retrieve Data Inside an Atom Another step towards quantum computing - the Holy Grail of data processing and storage - was achieved when an international team of scientists that included researchers with the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) were able to successfully store and retrieve information using the nucleus of an atom. New JILA technique reveals hidden properties of ultracold atomic gases Physicists at JILA, a joint institute of the National Institute of Standards and Technology (NIST) and the University of Colorado at Boulder, have demonstrated a powerful new technique that reveals hidden properties of ultracold atomic gases. UCSB researchers make milestone discovery in quantum mechanics Researchers at UC Santa Barbara have recently reached what they are calling a milestone in experimental quantum mechanics. The fight for the best quantum bit (qubit) Our results give us, for the first time, the possibility to understand the interaction between just two electrons placed next to each other in a carbon nanotube. UBC physicists develop 'impossible' technique to study and develop superconductors A team of University of British Columbia researchers has developed a technique that controls the number of electrons on the surface of high-temperature superconductors, a procedure considered impossible for the past two decades. Weizmann Institute Scientists Find New 'Quasiparticles' Weizmann Institute physicists have demonstrated, for the first time, the existence of 'quasiparticles' with one quarter the charge of an electron. This finding could be a first step toward creating exotic types of quantum computers that might be powerful, yet highly stable. McCormick Researchers Take Step Toward Creating Quantum Computers For now, full-fledged quantum computers are the stuff of science fiction - in last summer's blockbuster movie Transformers, the bad guys use quantum computing to break into the U.S. Army's secure files in just 10 seconds flat. Silicon chips for optical quantum technologies A team of physicists and engineers has demonstrated exquisite control of single particles of light - photons - on a silicon chip to make a major advance towards the long sought after goal of a super-powerful quantum computer. The future of computing -- carbon nanotubes and superconductors to replace the silicon chip The future of computing is under the spotlight at the Institute of Physics' Condensed Matter and Materials Physics conference at the Royal Holloway College of the University of London on 26-28 March. More Quantum Computer Current Events and Quantum Computer News Articles |
|||||||||||||||||||||
|
|||||||||||||||||||||
|
|||||||||||||||||||||