Quantum simulator with 51 qubits is largest ever

Technology 18 July 2017
MIT quantum simulator
To the power of 51


A team in the US has created a simulator with 51 quantum bits – the largest of its kind so far. Mikhail Lukin at Harvard University announced the achievement on 14 July at the International Conference on Quantum Technologies in Moscow.

Quantum simulators are used to model the minute behaviour of molecules, and could help study how drugs act within the human body. They aren’t full-blown quantum computers, though, says Simon Devitt at Macquarie University in Sydney.

Lukin’s system was specifically built to solve one equation that models the interactions between certain atoms. If you wanted to solve a different equation, you’d have to rebuild the system from scratch.


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Quantum computers, on the other hand, are theoretically capable of handling any equation you throw at them. But they are a much bigger challenge to build, says Devitt.

The simulator has a high error rate, but because it simulates just one mathematical model, it can still produce useful results some of the time. Full-blown quantum computers must achieve much lower error rates, but will produce better results.

Today’s most advanced quantum systems – such as the 49-qubit computer Google is working on – exploit superconductivity to store information, using electrons at extremely low temperatures.

Lukin’s work takes a different approach. His qubits are each made from a single rubidium atom, trapped in place using lasers and programmed via fluctuations in the laser beam.

Although less complex than quantum computers, simulators are still extremely expensive to build, says Devitt, so it’s unlikely that they will find many practical applications beyond physics departments for the time being.

And while this experiment show that it is possible to create large-scale quantum systems, we’ve still got a long way to go before we create universal quantum computers. “The full-blown quantum computer is the hardest system to get right,” Devitt says.

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