Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Quantum Computation: Fragile yet Error-free

13.06.2014

In a close collaborative effort, Spanish and Austrian physicists have experimentally encoded one quantum bit (qubit) in entangled states distributed over several particles and for the first time carried out simple computations on it. The 7-qubit quantum register could be used as the main building block for a quantum computer that corrects any type of error. The researchers’ results have now been published in Science.

Even computers are error-prone. The slightest disturbances may alter saved information and falsify the results of calculations. To overcome these problems, computers use specific routines to continuously detect and correct errors.


The 7-ion system applied for encoding one logical quantum bit can be used as a building block for much larger quantum systems. The bigger the lattice, the more robust it becomes. Illustration: IQOQI/Harald Ritsch

This also holds true for a future quantum computer, which will require procedures for error correction as well: “Quantum phenomena are extremely fragile and error-prone. Errors can spread rapidly and severely disturb the computer,” says Thomas Monz, member of Rainer Blatt’s research group at the Institute for Experimental Physics at the University of Innsbruck.

Together with Markus Müller and Miguel Angel Martin-Delgado from the Department for Theoretical Physics at the Complutense University in Madrid, the physicists in Innsbruck developed a new quantum error-correcting method and tested it experimentally. “A quantum bit is extremely complex and cannot be simply copied.

... more about:
»7-ion System »Fragile »Physics »Qubit »lattice »quantum bit »steps

Moreover, errors in the microscopic quantum world are more manifold and harder to correct than in conventional computers,” underlines Monz. “To detect and correct general errors in a quantum computer, we need highly sophisticated so-called quantum error-correcting codes.”

The topological code used for this current experiment was proposed by Martin-Delgado’s research group in Madrid. It arranges the qubits on a two-dimensional lattice, where they can interact with the neighboring particles.

A quantum bit encoded in seven ions

For the experiment at the University of Innsbruck the physicists confined seven calcium atoms in an ion trap, which allows them to cool these atoms to almost absolute zero temperature and precisely control them by laser beams. The researchers encoded the fragile quantum states of one logical qubit in entangled states of these particles. The quantum error-correcting code provided the program for this process.

“Encoding the logical qubit in the seven physical qubits was a real experimental challenge,” relates Daniel Nigg, a member of Rainer Blatt’s research group. The physicists achieved this in three steps, where in each step complex sequences of laser pulses were used to create entanglement between four neighboring qubits.

“For the first time we have been able to encode a single quantum bit by distributing its information over seven atoms in a controlled way,” says an excited Markus Müller, who in 2011 moved from Innsbruck to the Complutense University in Madrid. “When we entangle atoms in this specific way, they provide enough information for subsequent error correction and possible computations.”

Error-free operations

In another step the physicists tested the code’s capability to detect and correct different types of errors. “We have demonstrated that in this type of quantum system we are able to independently detect and correct every possible error for each particle,” says Daniel Nigg. “To do this we only need information about the correlations between the particles and don’t have to perform measurements of the single particles,” explains Daniel Nigg’s colleague Esteban Martinez.

In addition to reliably detecting single errors, the physicists were for the first time able to apply single or even repetitive operations on a logical encoded qubit. Once the obstacle of the complex encoding process is overcome, only simple single-qubit gate operations are necessary for each gate operation. “With this quantum code we can implement basic quantum operations and simultaneously correct all possible errors,” explains Thomas Monz this crucial milestone on the route towards a reliable and fault tolerant quantum computer.

Basis for future innovations

This new approach developed by the Spanish and Austrian physicists constitutes a promising basis for future innovations. “This 7-ion system applied for encoding one logical quantum bit can be used as a building block for much larger quantum systems,” says theoretical physicist Müller. “The bigger the lattice, the more robust it becomes. The result might be a quantum computer that could perform any number of operations without being impeded by errors.”

The current experiment not only opens new routes for technological innovations: “Here, completely new questions come up, for example which methods can be used in the first place to characterise such large logical quantum bits,” says Rainer Blatt with a view into the future. “Moreover, we would also like to collaboratively develop the used quantum codes further to optimize them for even more extensive operations,” adds Martin-Delgado.

The researchers are financially supported by the Spanish Ministry of Science, the Austrian Science Fund, the U.S. Government, the European Commission and the Federation of Austrian Industries Tyrol.

Publication: Quantum Computations on a Topologically Encoded Qubit. Daniel Nigg, Markus Müller, Esteban A. Martinez, Philipp Schindler, Markus Hennrich, Thomas Monz, Miguel Angel Martin-Delgado, and Rainer Blatt. Science 2014 DOI: 10.1126/science.1253742 (arXiv:1403.5426)

Contact
Thomas Monz
Institute for Experimental Physics
University of Innsbruck
phone: +43 512 507 52452
email: thomas.monz@uibk.ac.at

Markus Müller
Departamento de Fisica Teórica I
Universidad Complutense Madrid
phone: +34 91 394 4569
email: mueller@ucm.es

Christian Flatz
Public Relations
University of Innsbruck
phone: +43 512 507 32022
email: christian.flatz@uibk.ac.at

Weitere Informationen:

http://dx.doi.org/10.1126/science.1253742 - Quantum Computations on a Topologically Encoded Qubit. Daniel Nigg, Markus Müller, Esteban A. Martinez, Philipp Schindler, Markus Hennrich, Thomas Monz, Miguel Angel Martin-Delgado, and Rainer Blatt. Science 2014
http://www.quantumoptics.at - Quantum Optics and Spectroscopy Group


Dr. Christian Flatz | Universität Innsbruck
Further information:
http://www.uibk.ac.at

Further reports about: 7-ion System Fragile Physics Qubit lattice quantum bit steps

More articles from Physics and Astronomy:

nachricht New record in materials research: 1 terapascals in a laboratory
22.07.2016 | Universität Bayreuth

nachricht Mapping electromagnetic waveforms
22.07.2016 | Max-Planck-Institut für Quantenoptik

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: Mapping electromagnetic waveforms

Munich Physicists have developed a novel electron microscope that can visualize electromagnetic fields oscillating at frequencies of billions of cycles per second.

Temporally varying electromagnetic fields are the driving force behind the whole of electronics. Their polarities can change at mind-bogglingly fast rates, and...

Im Focus: Continental tug-of-war - until the rope snaps

Breakup of continents with two speed: Continents initially stretch very slowly along the future splitting zone, but then move apart very quickly before the onset of rupture. The final speed can be up to 20 times faster than in the first, slow extension phase.phases

Present-day continents were shaped hundreds of millions of years ago as the supercontinent Pangaea broke apart. Derived from Pangaea’s main fragments Gondwana...

Im Focus: A Peek into the “Birthing Room” of Ribosomes

Scaffolding and specialised workers help with the delivery – Heidelberg biochemists gain new insights into biogenesis

A type of scaffolding on which specialised workers ply their trade helps in the manufacturing process of the two subunits from which the ribosome – the protein...

Im Focus: New protocol enables analysis of metabolic products from fixed tissues

Scientists at the Helmholtz Zentrum München have developed a new mass spectrometry imaging method which, for the first time, makes it possible to analyze hundreds of metabolites in fixed tissue samples. Their findings, published in the journal Nature Protocols, explain the new access to metabolic information, which will offer previously unexploited potential for tissue-based research and molecular diagnostics.

In biomedical research, working with tissue samples is indispensable because it permits insights into the biological reality of patients, for example, in...

Im Focus: Computer Simulation Renders Transient Chemical Structures Visible

Chemists at the University of Basel have succeeded in using computer simulations to elucidate transient structures in proteins. In the journal Angewandte Chemie, the researchers set out how computer simulations of details at the atomic level can be used to understand proteins’ modes of action.

Using computational chemistry, it is possible to characterize the motion of individual atoms of a molecule. Today, the latest simulation techniques allow...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

GROWING IN CITIES - Interdisciplinary Perspectives on Urban Gardening

15.07.2016 | Event News

SIGGRAPH2016 Computer Graphics Interactive Techniques, 24-28 July, Anaheim, California

15.07.2016 | Event News

Partner countries of FAIR accelerator meet in Darmstadt and approve developments

11.07.2016 | Event News

 
Latest News

Hey robot, shimmy like a centipede

22.07.2016 | Information Technology

New record in materials research: 1 terapascals in a laboratory

22.07.2016 | Physics and Astronomy

University of Graz researchers challenge 140-year-old paradigm of lichen symbiosis

22.07.2016 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>