Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Quantum computers may be easier to build than predicted

03.03.2005


The new NIST architecture for quantum computing relies on several levels of error checking to ensure the accuracy of quantum bits (qubits). The image above illustrates how qubits are grouped in blocks to form the levels. To implement the architecture with three levels, a series of operations is performed on 36 qubits (bottom row)each one representing either a 1, a 0, or both at once. The operations on the nine sets of qubits produce two reliably accurate qubits (top row). The purple spheres represent qubits that are either used in error detection or in actual computations. The yellow spheres are qubits that are measured to detect or correct errors but are not used in final computations.


A full-scale quantum computer could produce reliable results even if its components performed no better than today’s best first-generation prototypes, according to a paper in the March 3 issue in the journal Nature* by a scientist at the Commerce Department’s National Institute of Standards and Technology (NIST).

In theory, such a quantum computer could be used to break commonly used encryption codes, to improve optimization of complex systems such as airline schedules, and to simulate other complex quantum systems.

A key issue for the reliability of future quantum computers--which would rely on the unusual properties of nature’s smallest particles to store and process data--is the fragility of quantum states. Today’s computers use millions of transistors that are switched on or off to reliably represent values of 1 or 0. Quantum computers would use atoms, for example, as quantum bits (qubits), whose magnetic and other properties would be manipulated to represent 1 or 0 or even both at the same time. These states are so delicate that qubit values would be unusually susceptible to errors caused by the slightest electronic "noise."



To get around this problem, NIST scientist Emanuel Knill suggests using a pyramid-style hierarchy of qubits made of smaller and simpler building blocks than envisioned previously, and teleportation of data at key intervals to continuously double-check the accuracy of qubit values. Teleportation was demonstrated last year by NIST physicists, who transferred key properties of one atom to another atom without using a physical link.

"There has been a tremendous gap between theory and experiment in quantum computing," Knill says. "It is as if we were designing today’s supercomputers in the era of vacuum tube computing, before the invention of transistors. This work reduces the gap, showing that building quantum computers may be easier than we thought. However, it will still take a lot of work to build a useful quantum computer."

Use of Knill’s architecture could lead to reliable computing even if individual logic operations made errors as often as 3 percent of the time--performance levels already achieved in NIST laboratories with qubits based on ions (charged atoms). The proposed architecture could tolerate several hundred times more errors than scientists had generally thought acceptable.

Knill’s findings are based on several months of calculations and simulations on large, conventional computer workstations. The new architecture, which has yet to be validated by mathematical proofs or tested in the laboratory, relies on a series of simple procedures for repeatedly checking the accuracy of blocks of qubits. This process creates a hierarchy of qubits at various levels of validation.

For instance, to achieve relatively low error probabilities in moderately long computations, 36 qubits would be processed in three levels to arrive at one corrected pair. Only the top-tier, or most accurate, qubits are actually used for computations. The more levels there are, the more reliable the computation will be.

Knill’s methods for detecting and correcting errors rely heavily on teleportation. Teleportation enables scientists to measure how errors have affected a qubit’s value while transferring the stored information to other qubits not yet perturbed by errors. The original qubit’s quantum properties would be teleported to another qubit as the original qubit is measured.

The new architecture allows trade-offs between error rates and computing resource demands. To tolerate 3 percent error rates in components, massive amounts of computing hardware and processing time would be needed, partly because of the "overhead" involved in correcting errors. Fewer resources would be needed if component error rates can be reduced further, Knill’s calculations show.

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

More articles from Physics and Astronomy:

nachricht Smallest transistor worldwide switches current with a single atom in solid electrolyte
17.08.2018 | Karlsruher Institut für Technologie (KIT)

nachricht Protecting the power grid: Advanced plasma switch for more efficient transmission
17.08.2018 | DOE/Princeton Plasma Physics Laboratory

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

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

Im Focus: Color effects from transparent 3D-printed nanostructures

New design tool automatically creates nanostructure 3D-print templates for user-given colors
Scientists present work at prestigious SIGGRAPH conference

Most of the objects we see are colored by pigments, but using pigments has disadvantages: such colors can fade, industrial pigments are often toxic, and...

Im Focus: Unraveling the nature of 'whistlers' from space in the lab

A new study sheds light on how ultralow frequency radio waves and plasmas interact

Scientists at the University of California, Los Angeles present new research on a curious cosmic phenomenon known as "whistlers" -- very low frequency packets...

Im Focus: New interactive machine learning tool makes car designs more aerodynamic

Scientists develop first tool to use machine learning methods to compute flow around interactively designable 3D objects. Tool will be presented at this year’s prestigious SIGGRAPH conference.

When engineers or designers want to test the aerodynamic properties of the newly designed shape of a car, airplane, or other object, they would normally model...

Im Focus: Robots as 'pump attendants': TU Graz develops robot-controlled rapid charging system for e-vehicles

Researchers from TU Graz and their industry partners have unveiled a world first: the prototype of a robot-controlled, high-speed combined charging system (CCS) for electric vehicles that enables series charging of cars in various parking positions.

Global demand for electric vehicles is forecast to rise sharply: by 2025, the number of new vehicle registrations is expected to reach 25 million per year....

Im Focus: The “TRiC” to folding actin

Proteins must be folded correctly to fulfill their molecular functions in cells. Molecular assistants called chaperones help proteins exploit their inbuilt folding potential and reach the correct three-dimensional structure. Researchers at the Max Planck Institute of Biochemistry (MPIB) have demonstrated that actin, the most abundant protein in higher developed cells, does not have the inbuilt potential to fold and instead requires special assistance to fold into its active state. The chaperone TRiC uses a previously undescribed mechanism to perform actin folding. The study was recently published in the journal Cell.

Actin is the most abundant protein in highly developed cells and has diverse functions in processes like cell stabilization, cell division and muscle...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

LaserForum 2018 deals with 3D production of components

17.08.2018 | Event News

Within reach of the Universe

08.08.2018 | Event News

A journey through the history of microscopy – new exhibition opens at the MDC

27.07.2018 | Event News

 
Latest News

Smallest transistor worldwide switches current with a single atom in solid electrolyte

17.08.2018 | Physics and Astronomy

Robots as Tools and Partners in Rehabilitation

17.08.2018 | Information Technology

Climate Impact Research in Hannover: Small Plants against Large Waves

17.08.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>