Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

NIST develops powerful method of suppressing errors in many types of quantum computers

24.04.2009
Researchers at the National Institute of Standards and Technology (NIST) have demonstrated a technique for efficiently suppressing errors in quantum computers. The advance could eventually make it much easier to build useful versions of these potentially powerful but highly fragile machines, which theoretically could solve important problems that are intractable using today's computers.

The new error-suppression method, described in the April 23 issue of Nature,* was demonstrated using an array of about 1,000 ultracold beryllium ions (electrically charged atoms) trapped by electric and magnetic fields.

Each ion can act as a quantum bit (qubit) for storing information in a quantum computer. These ions form neatly ordered crystals, similar to arrays of qubits being fabricated by other researchers using semiconducting and superconducting circuitry. Arrays like this potentially could be used as multi-bit quantum memories.

The new NIST technique counteracts a major threat to the reliability of quantum memories: the potential for small disturbances, such as stray electric or magnetic fields, to create random errors in the qubits. The NIST team applied customized sequences of microwave pulses to reverse the accumulation of such random errors in all qubits simultaneously.

"Simulations show that under appropriate conditions this method can reduce the error rate in quantum computing systems up to a hundred times more than comparable techniques. Our measurement results validate these predictions," says Hermann Uys, a NIST guest researcher who is a lead author of the paper. Uys is visiting from the Council for Scientific and Industrial Research, Pretoria, South Africa.

Co-lead author Michael J. Biercuk, a NIST post-doc, notes that correcting qubit errors after they occur will require extraordinary resources, whereas early suppression of errors is far more efficient, and improves the performance of subsequent error correction. The new NIST error-suppression method could enable quantum computers of various designs to achieve error rates far below the so-called fault-tolerance threshold of about 1 error in 10,000 computational operations (0.01 percent), Biercuk says. If error rates can be reduced below this level, building a useful quantum computer becomes considerably more realistic.

Quantum computers, by relying on the unusual properties of the atomic-scale world to store and process data, could someday break commonly used encryption codes, perform faster searches of enormous databases, and determine the most efficient schedules for everything from airlines to traveling salespeople. They could also simulate complex quantum systems that are too difficult to study using today's computers or through direct experiments. But first, practical quantum computers need to be built, and their components need to be reliable.

Unlike today's computers, which use transistors that are switched on or off to represent bit values of 1 or 0, quantum computers would manipulate the properties of qubits to represent 1 or 0 or-thanks to the peculiarities of the quantum world-both at the same time. But these "quantum states" are so delicate that qubit values would be highly susceptible to errors caused by the slightest electronic noise.

Under ideal conditions, and in the absence of deliberate manipulations, ion qubit states evolve in a predictable way, similar to a spinning top tipped from its vertical axis. Environmental interference can lead to a buildup of error, but the new NIST pulse method can reverse this accumulation, thus preserving the original state.

The NIST method is an adaptation of "spin echo" techniques used for decades to suppress errors in nuclear magnetic resonance (the basis of magnetic resonance imaging). In spin echo, evenly spaced control pulses will nearly reverse the buildup of error, as long as fluctuations are slow relative to the time between pulses.

Recently, scientists at another institution published a theory of how to modify pulse timing in order to improve noise suppression. The NIST team conducted the first experimental demonstration of this theory, and then extended these ideas by generating novel pulse sequences tailored to the ambient noise environment. These novel sequences can be found quickly through an experimental feedback technique, and were shown to significantly outperform other sequences without the need for any knowledge of the noise characteristics. The researchers tested these pulse sequences under realistic noise conditions simulating those appropriate for different qubit technologies, making their results broadly applicable.

The research was conducted in the laboratory of NIST physicist John J. Bollinger, the project lead, and funded in part by the Intelligence Advanced Research Projects Agency.

* M.J. Biercuk, H. Uys, A.P. VanDevender, N. Shiga, W.M. Itano and J.J. Bollinger. Optimized Dynamical Decoupling in a Model Quantum Memory. Nature. April 23.

Laura Ost | EurekAlert!
Further information:
http://www.nist.gov

More articles from Information Technology:

nachricht Study suggests buried Internet infrastructure at risk as sea levels rise
17.07.2018 | University of Wisconsin-Madison

nachricht Microscopic trampoline may help create networks of quantum computers
17.07.2018 | University of Colorado at Boulder

All articles from Information Technology >>>

The most recent press releases about innovation >>>

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

Im Focus: First evidence on the source of extragalactic particles

For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.

To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...

Im Focus: Magnetic vortices: Two independent magnetic skyrmion phases discovered in a single material

For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.

Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...

Im Focus: Breaking the bond: To take part or not?

Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.

A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...

Im Focus: New 2D Spectroscopy Methods

Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.

"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....

Im Focus: Chemical reactions in the light of ultrashort X-ray pulses from free-electron lasers

Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.

Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Leading experts in Diabetes, Metabolism and Biomedical Engineering discuss Precision Medicine

13.07.2018 | Event News

Conference on Laser Polishing – LaP: Fine Tuning for Surfaces

12.07.2018 | Event News

11th European Wood-based Panel Symposium 2018: Meeting point for the wood-based materials industry

03.07.2018 | Event News

 
Latest News

Microscopic trampoline may help create networks of quantum computers

17.07.2018 | Information Technology

In borophene, boundaries are no barrier

17.07.2018 | Materials Sciences

The role of Sodium for the Enhancement of Solar Cells

17.07.2018 | Power and Electrical Engineering

VideoLinks
Science & Research
Overview of more VideoLinks >>>