Quantum Computers May Be Easier To Build Than Predicted

PHYSICS

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.

Gaithersburg MD (SPX) Mar 03, 2005
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.

*Knill, E. 2005. "Quantum computing with realistically noisy devices." Nature. March 3.

TECH SPACE

Scientists Entice Superconducting Devices To Act Like Atoms

Gaithersburg MD (SPX) Feb 28, 2005
Two superconducting devices have been coaxed into a special, interdependent state that mimics the unusual interactions sometimes seen in pairs of atoms, according to a team of physicists at the National Institute of Standards and Technology (NIST) and University of California, Santa Barbara (UCSB).

Thanks for being here; We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain. With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords. Our news coverage takes time and effort to publish 365 days a year. If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.
SpaceDaily Contributor $5 Billed Once credit card or paypal		SpaceDaily Monthly Supporter $5 Billed Monthly paypal only

The content herein, unless otherwise known to be public domain, are Copyright 1995-2016 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement All images and articles appearing on Space Media Network have been edited or digitally altered in some way. Any requests to remove copyright material will be acted upon in a timely and appropriate manner. Any attempt to extort money from Space Media Network will be ignored and reported to Australian Law Enforcement Agencies as a potential case of financial fraud involving the use of a telephonic carriage device or postal service.