How to certify a quantum computer

November 5, 2018, Swiss National Science Foundation
Credit: CC0 Public Domain

Quantum computers are being developed by teams working not only at universities but also at Google, IBM, Microsoft and D-Wave, a start-up company. And things are evolving quickly, says Nicolas Sangouard, SNSF Professor at the University of Basel. "In a few years at most, I expect the computing power of quantum computers to significantly outstrip the computing power of ordinary computers. We call that 'quantum supremacy'".

Sangouard and his co-workers recently showed how to check that these computers are fit for purpose. For they are not just powerful but also very delicate: some operate at as low as 270 degrees below zero. The researchers' approach enables them to certify all the components of a quantum computer – from short- and , to information processors, to the converters required to connect the computer to a secure quantum communications network. The protocol offers an additional advantage: it only uses the components already in the computer, thus obviating the need for additional devices. In principle, the protocol will work with any type of quantum computer, whatever the technology behind it.

A machine that tests itself

"The power of quantum computers is what makes them difficult to certify," says Sangouard. "Even the fastest ordinary computers are too slow to check the calculations made by such devices." Moreover, quantum computers will eventually be able to communicate with each other securely through a dedicated quantum communications network. So it's important to make sure that they aren't a weak link, says Sangouard.

That's why the research team has developed a completely quantum certification method that uses the computer's own building blocks. "We were inspired by Bell tests, which were devised by a physicist working at CERN in the 1960s," says Sangouard. "Normally, these tests are used to check whether particles are behaving according to quantum rules. We modified the tests to enable them to check the operation of the various components of a quantum . Because such a device is basically capable of doing the tests, our procedure is very simple to set up and doesn't require any special skills."

"What prompted the project was a seminar talk by a scientist invited to the University of Basel," says Sangouard. "The talk dealt with a complicated aspect of , but we were motivated to translate it into a useful method for computers. For me, that's a perfect example of how a conference is not just a means of learning in a passive way but also offers significant opportunities to innovate."

Explore further: First proof of quantum computer advantage

More information: Pavel Sekatski et al. Certifying the Building Blocks of Quantum Computers from Bell's Theorem, Physical Review Letters (2018). DOI: 10.1103/PhysRevLett.121.180505

Related Stories

First proof of quantum computer advantage

October 18, 2018

For many years, quantum computers were not much more than an idea. Today, companies, governments and intelligence agencies are investing in the development of quantum technology. Robert König, professor for the theory of ...

OpenFermion practice tool for quantum computer coding

March 29, 2018

In a global effort, researchers are working toward quantum computers. In the meantime, they have to learn how to write code for these devices, which are fundamentally different from conventional computers. A collaboration ...

The exciting new age of quantum computing

October 25, 2016

What does the future hold for computing? Experts at the Networked Quantum Information Technologies Hub (NQIT), based at Oxford University, believe our next great technological leap lies in the development of quantum computing.

Recommended for you

Rapid and continuous 3-D printing with light

January 22, 2019

Three-dimensional (3-D) printing, also known as additive manufacturing (AM), can transform a material layer by layer to build an object of interest. 3-D printing is not a new concept, since stereolithography printers have ...

Scientists discover new quantum spin liquid

January 22, 2019

An international research team led by the University of Liverpool and McMaster University has made a significant breakthrough in the search for new states of matter.

Researchers capture an image of negative capacitance in action

January 21, 2019

For the first time ever, an international team of researchers imaged the microscopic state of negative capacitance. This novel result provides researchers with fundamental, atomistic insight into the physics of negative capacitance, ...

Toward ultrafast spintronics

January 21, 2019

Electronics have advanced through continuous improvements in microprocessor technology since the 1960s. However, this process of refinement is projected to stall in the near future due to constraints imposed by the laws of ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.