Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


NIST demonstrates data ’repair kit’ for quantum computers


A practical method for automatically correcting data-handling errors in quantum computers has been developed and demonstrated by physicists at the National Institute of Standards and Technology (NIST).

An ion’s quantum state can be spin up (top), spin down (middle) or a superposition state, represented graphically as any one of many possible spin directions in between up and down (bottom). Superposition states in which the spin is depicted as horizontal will be measured as spin up 50 percent of the time and spin down 50 percent of the time. Graphic credit: Kelly Talbott/NIST

Described in the Dec. 2, 2004, issue of the journal Nature, the NIST work is the first demonstration of all the steps of error correction for quantum computers, a futuristic, potentially very powerful form of computing that uses the quantum properties of atoms or other particles as 1s and 0s for processing data. The method was implemented using ions (electrically charged atoms) as quantum bits (qubits). Ions are arguably the leading candidate for use as qubits in a quantum computer.

Conventional computers use electronic switches that are either on or off to represent 1s and 0s that then can be stored or manipulated to make calculations. Quantum computing would use the quantum states of matter (such as magnetic properties) as 1s, 0s---or even both at once. The unusual features of the quantum world provide extra computational power, offering the prospect of carrying out a massive number of simultaneous calculations to solve problems that are impossible to solve today. Specific applications could include code-breaking of unprecedented power, faster database searching, fraud-proof digital signatures and optimization of everything from communications systems to airline schedules. But unless data-handling errors are corrected, "noise" caused by environmental disturbances, such as fluctuating magnetic fields associated with electrical equipment, could diminish any gains over today’s computers.

The new NIST method helps to ensure the correctness of data during computations by creating redundant data sets, or what might be called quantum backup copies. "The basic concept is a familiar one: If someone doesn’t understand what you say, you repeat it several times, and eventually they’ll get it," explains physicist Dietrich Leibfried, who developed the approach and helped to demonstrate its feasibility in NIST’s Boulder, Colo., laboratories.

Direct copying of qubits is prohibited by the rules of quantum mechanics, nature’s instruction book for the smallest particles of matter. Like all known quantum error correction methods, the NIST method gets around this obstacle by exploiting a famously spooky (the term used by Einstein) feature of quantum mechanics that allows the "entanglement" of physically separated atoms to link their quantum properties in predictable ways. The atoms also are prepared in a special "superposition" state in which they represent both 1 and 0 at the same time.

The demonstration used three beryllium ions as qubits. One "primary" ion is entangled with two "helper" ions as part of a series of encoding steps. The primary qubit is essential to the computation; the other two are expendable. Because the three are entangled, errors in one affect the others, a condition that is reflected in the joint quantum state of all three qubits. If the quantum state of the primary qubit is accidentally changed, the mistake can be detected and corrected by reversing the steps to decode the data, and then measuring the values of the two extra qubits.

Unlike other demonstrations of quantum error correction, the NIST approach makes corrections based on actual measurements, allows qubits to be "reset" on the fly, and could be scaled up for use in quantum computers of practical size and utility. Previous demonstrations by other groups have involved correction of errors in qubits made of molecules in a liquid, without the ability to measure or reset and reuse the extra qubits needed to detect errors. The ability to "empty the trash bin," rather than simply storing mistakes somewhere in the computer, makes the NIST approach more practical.

The NIST error correction process could be incorporated into the programs executed by quantum computers. In principle, the approach could be used to maintain the fragile quantum states of ions or atoms by repeated error correction during data processing, an essential step toward scalable, reliable quantum computers. The same NIST research group previously demonstrated other essential components for a quantum computer based on atomic-ion traps.

Error correction is routine in today’s computing and communications systems. For instance, a sender might periodically add up a series of sent bit values and transmit the total to the receiver. Once the same bits are received, the values are also summed at the receiver and the two totals are compared. If the totals match, there is a high probability that the bits arrived in the correct state. If the totals differ, then the data were corrupted, and the original bits are re-sent. This approach would fail in quantum information systems because measuring a qubit destroys its quantum state and effectively stops the computation. Therefore, errors need to be detected indirectly, as in the NIST method. It is not necessary to know the value of the primary qubit in order to detect an error and correct it.

To verify that the method works, NIST scientists performed many experiments with beryllium ion qubits and compared the corrected quantum states to the initial and uncorrected states. The instrumentation and procedures for manipulating qubits need to be improved to build reliable quantum computers, but such improvements seem feasible, Leibfried says. In addition, more ions and a more complex approach would be needed to correct all possible types of errors.

Laura Ost | EurekAlert!
Further information:

More articles from Physics and Astronomy:

nachricht Researchers at Fraunhofer monitor re-entry of Chinese space station Tiangong-1
21.03.2018 | Fraunhofer-Institut für Hochfrequenzphysik und Radartechnik FHR

nachricht Taming chaos: Calculating probability in complex systems
21.03.2018 | American Institute of Physics

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: Researchers Discover New Anti-Cancer Protein

An international team of researchers has discovered a new anti-cancer protein. The protein, called LHPP, prevents the uncontrolled proliferation of cancer cells in the liver. The researchers led by Prof. Michael N. Hall from the Biozentrum, University of Basel, report in “Nature” that LHPP can also serve as a biomarker for the diagnosis and prognosis of liver cancer.

The incidence of liver cancer, also known as hepatocellular carcinoma, is steadily increasing. In the last twenty years, the number of cases has almost doubled...

Im Focus: Researchers at Fraunhofer monitor re-entry of Chinese space station Tiangong-1

In just a few weeks from now, the Chinese space station Tiangong-1 will re-enter the Earth's atmosphere where it will to a large extent burn up. It is possible that some debris will reach the Earth's surface. Tiangong-1 is orbiting the Earth uncontrolled at a speed of approx. 29,000 km/h.Currently the prognosis relating to the time of impact currently lies within a window of several days. The scientists at Fraunhofer FHR have already been monitoring Tiangong-1 for a number of weeks with their TIRA system, one of the most powerful space observation radars in the world, with a view to supporting the German Space Situational Awareness Center and the ESA with their re-entry forecasts.

Following the loss of radio contact with Tiangong-1 in 2016 and due to the low orbital height, it is now inevitable that the Chinese space station will...

Im Focus: Alliance „OLED Licht Forum“ – Key partner for OLED lighting solutions

Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP, provider of research and development services for OLED lighting solutions, announces the founding of the “OLED Licht Forum” and presents latest OLED design and lighting solutions during light+building, from March 18th – 23rd, 2018 in Frankfurt a.M./Germany, at booth no. F91 in Hall 4.0.

They are united in their passion for OLED (organic light emitting diodes) lighting with all of its unique facets and application possibilities. Thus experts in...

Im Focus: Mars' oceans formed early, possibly aided by massive volcanic eruptions

Oceans formed before Tharsis and evolved together, shaping climate history of Mars

A new scenario seeking to explain how Mars' putative oceans came and went over the last 4 billion years implies that the oceans formed several hundred million...

Im Focus: Tiny implants for cells are functional in vivo

For the first time, an interdisciplinary team from the University of Basel has succeeded in integrating artificial organelles into the cells of live zebrafish embryos. This innovative approach using artificial organelles as cellular implants offers new potential in treating a range of diseases, as the authors report in an article published in Nature Communications.

In the cells of higher organisms, organelles such as the nucleus or mitochondria perform a range of complex functions necessary for life. In the networks of...

All Focus news of the innovation-report >>>



Industry & Economy
Event News

Virtual reality conference comes to Reutlingen

19.03.2018 | Event News

Ultrafast Wireless and Chip Design at the DATE Conference in Dresden

16.03.2018 | Event News

International Tinnitus Conference of the Tinnitus Research Initiative in Regensburg

13.03.2018 | Event News

Latest News

Modular safety concept increases flexibility in plant conversion

22.03.2018 | Trade Fair News

New interactive map shows climate change everywhere in world

22.03.2018 | Earth Sciences

New technologies and computing power to help strengthen population data

22.03.2018 | Earth Sciences

Science & Research
Overview of more VideoLinks >>>