'Coated' qubit remains stable 10 times longer

19th October 2016

UNSW (University of New South Wales) Australia

Enaie Azambuja

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Researchers from the University of New South Wales, Australia have created a “coated” qubit that remains stable 10 times longer than previously possible. This advancement allows for longer calculations in quantum computers. The research, published in Nature Communications, tackles one of the core applications of quantum mechanics to the world of computers. Quantum computers can be fast thanks to a property called superposition, where different states are all processed at the same time.

Unfortunately, superposition can quickly be lost due to interactions with both matter and light. "The greatest hurdle in using quantum objects for computing is to preserve their delicate superpositions long enough to allow us to perform useful calculations," added Andrea Morello, leader of the research team.

To keep the quantum system stable, they placed a phosphorus atom inside a silicon chip. The atom is placed in a very strong electromagnetic field continuously oscillating at microwave frequencies. Usually, the stability depends on the amplitude of the oscillation, but by using the frequency the team was able to neutralise the effect of random noise.

"This new 'dressed qubit' can be controlled in a variety of ways that would be impractical with an 'undressed qubit'," explained Morello. "For example, it can be controlled by simply modulating the frequency of the microwave field, just like in an FM radio. The 'undressed qubit' instead requires turning the amplitude of the control fields on and off, like an AM radio.

"In some sense, this is why the dressed qubit is more immune to noise: the quantum information is controlled by the frequency, which is rock-solid, whereas the amplitude can be more easily affected by external noise."

It also important that the quantum bit was contained in a silicon chip, which is the industrial standard for computing technology, meaning quantum processors can be built using a fabrication process already in use.

Quantum computers will be able to search huge databases, solving complex math and even model intricate biological and chemical interactions in ways that surpass today's most advanced computers.