Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Quantum bugs, meet your new swatter

20.08.2018

Rice University scientist leads development of efficient method to characterize quantum computers

A Rice University computer scientist and his colleagues have proposed a method to accelerate and simplify the imposing task of diagnosing quantum computers.


An illustration shows rubidium atom qubits isolated by scientists at the National Institute of Standards and Technology and proposed for use in quantum computers. A team led by Rice University computer scientist Anastasios Kyrillidis has proposed a scalable algorithm to significantly accelerate the task of validating the accuracy of quantum computers.

Credit: NIST

Usage Restrictions: For news reporting purposes only.

Anastasios Kyrillidis, an assistant professor of computer science who joined Rice this year, led the development of a nonconventional method as a diagnostic tool for powerful, next-generation computers that depend on the spooky actions of quantum bits -- aka qubits -- which are switches that operate under rules that differ from the 1s and 0s in classical computers.

Quantum computers exploit the principles of quantum mechanics to quickly solve tough problems that would take far longer on conventional supercomputers. They promise future breakthroughs in drug design, advanced materials, cryptography and artificial intelligence.

An open-access paper by Kyrillidis and his team appears in the Nature journal Quantum Information.

Like any new hardware, Kyrillidis said, quantum computer systems are prone to bugs that need to be squashed. That takes continuous testing to validate their capabilities. The sheer complexity of quantum computers that do exponentially more with every bit requires an immense amount of validation, he said.

Kyrillidis' method focuses on quantum state tomography, a process inspired by medical tomography in which images of a body are captured in slices that are later reassembled into a three-dimensional map. Quantum state tomography differs, he said, as it takes "images" of the state of a quantum computer's qubits.

"When a quantum computer executes an algorithm, it starts at a specific state; think of it as the input to the algorithm," Kyrillidis said. "As the computer progresses through steps of the algorithm, it's going through many states. The state at the very end is the answer to your algorithm's question."

By reassembling the full state from these measurements, Kyrillidis said one can later pinpoint hardware or software errors that may have caused the computer to deliver unexpected results.

That takes a lot of measurements, and the computational cost of reconstruction can be high, even for classical computers, he said. Tomography-based analysis of quantum computers with even as few as five or six qubits would be prohibitive without somehow simplifying the task - and state-of-the-art machines have 50 qubits or more.

Qubits are the basic units of information in a quantum computer. Like a bit in a classical computer, each qubit can represent either 1 or 0. Unlike a bit, a qubit can also represent 1 and 0 simultaneously, a state called superposition that exponentially raises the number of calculations an array of qubits can perform at once. To make it more interesting, the state of the qubit as determined by magnetic polarization or electron spin only exists when it's measured.

Kyrillidis said even a modest increase in the number of qubits in a computer dramatically increases its power.

"In a system with five qubits, the state can be represented by a 2-to-the-5 times 2-to-the-5 matrix, so it's a 32-by-32 matrix," he said. "That's not big. But in a 20-qubit system like the one at IBM, the state can be characterized by a million-by-million matrix. If we were taking full measurements with regular tomography techniques, we would need to poll the system roughly a million-squared times in order to get enough information to recover its state."

Kyrillidis and his team solved the validation problem with an algorithm they call Projected Factored Gradient Decent (ProjFGD). It takes advantage of compressed sensing, a method that minimizes the amount of incoming data while still ensuring accurate results. He said the method would cut the number of measurements for a 20-qubit system to a mere million or so. "That's still a big number, but much smaller than a million squared," he said.

Kyrillidis noted that IBM, where he spent a year as a research scientist before coming to Rice, has put a quantum computer in the cloud where anyone can access it and run programs. He said the company reasons that the more people learn about programming for quantum computers now, the more mature their skills will be when the platform comes of age. But there's a side benefit for him, as it gives him a ready platform to test ProjFGD.

"The quantum state tomography tool is generic, and has more to do with the nature of the qubit rather than the specific architecture," Kyrillidis said. "As quantum computers get more powerful, it can definitely be scaled up to certify systems."

###

Co-authors are Amir Kalev of the University of Maryland, Dohyung Park of Facebook, Srinadh Bhojanapalli of the Toyota Technological Institute at Chicago, and Constantine Caramanis and Sujay Sanghavi of the University of Texas at Austin.

An IBM Goldstine Fellowship and the Department of Defense supported the research.

Read the paper at https://www.nature.com/articles/s41534-018-0080-4.

This news release can be found online at http://news.rice.edu/2018/08/19/quantum-bugs-meet-your-new-swatter/

Follow Rice News and Media Relations via Twitter @RiceUNews.

Related materials:

Anastasios Kyrillidis: https://csweb.rice.edu/tasos-kyrillidis

Rice Department of Computer Science: https://csweb.rice.edu

George R. Brown School of Engineering: https://engineering.rice.edu

Located on a 300-acre forested campus in Houston, Rice University is consistently ranked among the nation's top 20 universities by U.S. News & World Report. Rice has highly respected schools of Architecture, Business, Continuing Studies, Engineering, Humanities, Music, Natural Sciences and Social Sciences and is home to the Baker Institute for Public Policy. With 3,970 undergraduates and 2,934 graduate students, Rice's undergraduate student-to-faculty ratio is just under 6-to-1. Its residential college system builds close-knit communities and lifelong friendships, just one reason why Rice is ranked No. 1 for lots of race/class interaction and No. 2 for quality of life by the Princeton Review. Rice is also rated as a best value among private universities by Kiplinger's Personal Finance. To read "What they're saying about Rice," go to http://tinyurl.com/RiceUniversityoverview.

Media Contact

David Ruth
david@rice.edu
713-348-6327

 @RiceUNews

http://news.rice.edu 

David Ruth |
Further information:
http://dx.doi.org/10.1038/s41534-018-0080-4

More articles from Information Technology:

nachricht One Step Ahead: Adaptive Radar Systems for Smart Driver Assistance
20.09.2018 | Fraunhofer-Institut für Hochfrequenzphysik und Radartechnik FHR

nachricht Enjoying virtual-reality-entertainment without headache or motion sickness
19.09.2018 | Fraunhofer-Institut für Organische Elektronik, Elektronenstrahl- und Plasmatechnik FEP

All articles from Information Technology >>>

The most recent press releases about innovation >>>

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

Im Focus: Scientists present new observations to understand the phase transition in quantum chromodynamics

The building blocks of matter in our universe were formed in the first 10 microseconds of its existence, according to the currently accepted scientific picture. After the Big Bang about 13.7 billion years ago, matter consisted mainly of quarks and gluons, two types of elementary particles whose interactions are governed by quantum chromodynamics (QCD), the theory of strong interaction. In the early universe, these particles moved (nearly) freely in a quark-gluon plasma.

This is a joint press release of University Muenster and Heidelberg as well as the GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt.

Then, in a phase transition, they combined and formed hadrons, among them the building blocks of atomic nuclei, protons and neutrons. In the current issue of...

Im Focus: Patented nanostructure for solar cells: Rough optics, smooth surface

Thin-film solar cells made of crystalline silicon are inexpensive and achieve efficiencies of a good 14 percent. However, they could do even better if their shiny surfaces reflected less light. A team led by Prof. Christiane Becker from the Helmholtz-Zentrum Berlin (HZB) has now patented a sophisticated new solution to this problem.

"It is not enough simply to bring more light into the cell," says Christiane Becker. Such surface structures can even ultimately reduce the efficiency by...

Im Focus: New soft coral species discovered in Panama

A study in the journal Bulletin of Marine Science describes a new, blood-red species of octocoral found in Panama. The species in the genus Thesea was discovered in the threatened low-light reef environment on Hannibal Bank, 60 kilometers off mainland Pacific Panama, by researchers at the Smithsonian Tropical Research Institute in Panama (STRI) and the Centro de Investigación en Ciencias del Mar y Limnología (CIMAR) at the University of Costa Rica.

Scientists established the new species, Thesea dalioi, by comparing its physical traits, such as branch thickness and the bright red colony color, with the...

Im Focus: New devices based on rust could reduce excess heat in computers

Physicists explore long-distance information transmission in antiferromagnetic iron oxide

Scientists have succeeded in observing the first long-distance transfer of information in a magnetic group of materials known as antiferromagnets.

Im Focus: Finding Nemo's genes

An international team of researchers has mapped Nemo's genome

An international team of researchers has mapped Nemo's genome, providing the research community with an invaluable resource to decode the response of fish to...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

"Boston calling": TU Berlin and the Weizenbaum Institute organize a conference in USA

21.09.2018 | Event News

One of the world’s most prominent strategic forums for global health held in Berlin in October 2018

03.09.2018 | Event News

4th Intelligent Materials - European Symposium on Intelligent Materials

27.08.2018 | Event News

 
Latest News

Astrophysicists measure precise rotation pattern of sun-like stars for the first time

21.09.2018 | Physics and Astronomy

Brought to light – chromobodies reveal changes in endogenous protein concentration in living cells

21.09.2018 | Life Sciences

"Boston calling": TU Berlin and the Weizenbaum Institute organize a conference in USA

21.09.2018 | Event News

VideoLinks
Science & Research
Overview of more VideoLinks >>>