Researchers Develop Quantum Device To Control Single Electron Spin

Quantum computing is still out of reach for most mainstream industries, but continuing research in the field is making the technology more accessible. A team of engineers at the University at Buffalo have developed a semiconductor that can trap, detect and manipulate the single spin of an electron.

"The task of manipulating the spin of single electrons is a hugely daunting technological challenge that has the potential, if overcome, to open up new paradigms of nanoelectronics," said Jonathan P. Bird, Ph.D., professor of electrical engineering in the UB School of Engineering and Applied Sciences and principal investigator on the project.

The research paper (PDF) detailing the advancement is featured in this week’s Physical Review Letters. "In this paper, we demonstrate a novel approach that allows us to easily trap, manipulate and detect single-electron spins, in a scheme that has the potential to be scaled up in the future into dense, integrated circuits," added Bird.

The system developed at UB steers the electrical current in a semiconductor by applying voltage to nanoscale gaps on select metallic gates that are fabricated on its surface.

"As we increase the charge on the gates, this begins to close that gap," explained Bird, "allowing fewer and fewer electrons to pass through until eventually they all stop going through. As we squeeze off the channel, just before the gap closes completely, we can detect the trapping of the last electron in the channel and its spin."

"It was recently predicted that it should be possible to use these constrictions to trap single spins," added Bird. "In this paper, we provide evidence that such trapping can, indeed, be achieved with quantum point contacts and that it may also be manipulated electrically."

While prior efforts to trap a single spin using nanoscale semiconductors were proven successful, they had to operate at extremely cold temperatures – below 1 kelvin. According to UB researchers, cooling apparatus required to lower the temperature to such levels is not easily attainable. On the other hand, the device developed at UB is capable of performing at 20 kelvins – a temperature that the researchers believe makes their technology a more viable alternative.

Other recent advancements in quantum computing include the discovery of a "hidden" order in a quantum spin liquid, paving the way for a large number of electron spins can be coupled together to yield a quantum mechanical state with no classical analog. Scientists were also able to use pulses of light to accelerate quantum computers. Most recently, scientists at the NIST have successfully transferred data from one qubit to another by means of a microfabricated aluminum cable.

Such advancements are slowly but steadily leading up to the commercialization of quantum computer technology. Canadian firm D-Wave Systems unveiled and demonstrated earlier this year its own quantum computing technology that it aims for the commercial market – though D-Wave’s claims were met with some scepticism from the scientific community.

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