Noise-cancelling breakthrough to accelerate quantum computer tech

16 Sep 2019


Researchers have found a way to keep things quiet around quantum computers, which could make their blistering computational speeds more precise.

In order to perform the number of computations that far exceed even the most powerful binary supercomputers today, quantum computers need as little interference ‘noise’ as possible. Now, researchers from Dartmouth College and MIT have designed and conducted the first lab test that could help usher in more precise qubit systems.

Writing in Nature Communications, the computer scientists said this lab test successfully detected and characterised a class of complex ‘non-Gaussian’ noise processes. While most unwanted noise can be referred to as Gaussian, non-Gaussian noise is harder to describe and detect because it is so hard to predict.

A quantum computer that cannot sense non-Gaussian noise could be easily confused between the quantum signal it is supposed to process and unwanted noise in the system. Qubits have so far shown themselves to be good sensors of Gaussian noise, on which research has been developed to create techniques similar to how noise-cancelling headphones work.

Now, as part of this latest work, researchers were able to approximate characteristics of non-Gaussian noise using information about correlations at three different times, corresponding to what is known as the ‘bispectrum’ in the frequency domain.

A step towards reliable quantum computers

“This is the first time that a detailed, frequency-resolved characterisation of non-Gaussian noise has been able to be done in a lab with qubits,” said Lorenza Viola, who led the theory component of the research.

“This result significantly expands the toolbox that we have available for doing accurate noise characterisation and therefore crafting better and more stable qubits in quantum computers.”

While the MIT experiment to validate the protocol won’t immediately make large-scale quantum computers practically viable, it is a major step toward making them more precise. Years of work is still needed to perfect the detection and cancellation of noise in quantum system, but future research will look to move from a single-sensor system to a two-sensor system.

Co-author of the study, Leigh Norris, said: “The big barrier preventing us from having large-scale quantum computers now is this noise issue.

“This research moves us toward understanding the noise, which is a step toward cancelling it, and hopefully having a reliable quantum computer one day.”

Colm Gorey was a senior journalist with Silicon Republic