New Discovery in Silicon Carbide by University of Chicago Research Team
수정일 2017년 06월 24일 토요일
등록일 2018년 12월 31일 월요일

Photo source: Benjah-bmm27 via wikimedia commons

The University of Chicago Institute for Molecular Engineering led an International team to a new discovery.  They figured out how to manipulate a bizarre quantum interface between matter and light that resides in silicon carbide and moves along wavelengths used in telecommunications.

Prof.David Awschalom and his 13 co-authors announced their discovery in the June 23 issue of Physical Review X.  "Silicon carbide is currently used to build a wide variety of classical electronic devices today," said Awschalom, the Liew Family Professor in Molecular Engineering at UChicago and a senior scientist at Argonne National Laboratory.

This work moves forward the possibility of taking existing optical fiber networks and applying mechanical principles for geographically distributed quantum computation and secure communications.  Awschalom said "All of the processing protocols are in place to fabricate small quantum devices out of this material.These results offer a pathway for bringing quantum physics into the technological world."

The team's findings are based in part on theoretical models of materials performed by Awschalom's co-authors from the Hungarian Academy of Sciences in Budapest.  Sweden's Linkoping University had another research group grow most of the silicon carbide material that Awschalom and his team used at the University of Chicago labs.

Awschalom's team received some help from a team in Japan at the National Institutes for Quantum and Radiological Science and Technology.  They helped the UChicago researchers make quantum defects in the materials by irradiating them with electron beams.

The behavior of matter is governed by the quantum mechanics at the atomic and subatomic levels in counterintuitive and exotic ways, in comparison the typical day to day process of classical physics.  The new discovery relies on a quantum interface inside atomic-scale defects in silicon carbide which generates the fragile property of entanglement, definitely one of the strangest phenomena predicted by quantum mechanics.

What entanglement means is that two particles may be so inextricably connected that one particle's state instantly influences the others, whatever the distance between the two could be.  Awschalom said, "This non-intuitive nature of quantum mechanics might be exploited to ensure that communications between two parties are not intercepted or altered."

Awschalom stated what these findings do is enhance the surprising opportunity to create and also control quantum states within materials that already have technological applications.  Also saying pursuing the scientific and technological potential of such advances will become the focus of the newly announced Chicago Quantum Exchange.  Awschalom will direct this team.

One very intriguing aspect of the new findings is that silicon carbide semiconductor defects have a natural affinity for moving information between light and spin (a magnetic property of electrons).  David Christle, a postdoctoral scholar at the University of Chicago and lead author of the work said, "A key unknown has always been whether we could find a way to convert their quantum states to light.  We knew a light-matter interface should exist, but we might have been unlucky and found it to be intrinsically unsuitable for generating entanglement.He also stated, "We were very fortuitous in that the optical transitions and the process that converts the spin to light is of very high quality."

The defect turns out to be a missing atom which causes nearby atoms in the material to rearrange their electrons.The missing atom, or the defect itself, makes up an electronic state that researchers control with a tunable infrared laser.  Abram Falk, a researcher at the IBM Thomas J.Watson Research Center in Yorktown Heights, N.Y., who is familiar with the work but not a co-author on the paper said, "What quality basically means is: How many photons can you get before you've destroyed the quantum state of the spin?"

What the UChicago team did find was that they could potentially generate up to 10,000 photons, or packets of light, before they destroyed the spin state. "That would be a world record in terms of what you could do with one of these types of defect states," Falk said.  They succeeded in turning the quantum state of information from single electron spins in commercial wafers of silicon carbide into light and read it out with an efficiency of approximately 95 percent.

Falk explained "There's about a billion-dollar industry of power electronics built on silicon carbide, he said, "Following this work, there's an opportunity to build a platform for quantum communication that leverages these very advanced classical devices in the semiconductor industry."

Awschalom and his team attained a spin state (which is termed coherence) duration of one millisecond.  This does not sound like much for everyday clock timing, but it's a great amount in the realm of quantum states, where multiple calculations are carried out in nanoseconds or even a billionth of a second.

This achievement brings a plethora of possibilities to the table in silicon carbide because it's the nanoscale defects that new technologies seek for use with quantum mechanical properties in quantum information processing that senses magnetic and electric fields and temperature with nanoscale resolution, and secure communications using light.

Falk also iterated, most researchers studying defects for quantum applications have been zeroed in on an atomic defect in diamond, which has become a popular visible-light testbed for these technologies.  "Diamond has been this huge industry of quantum control work," Falk stated Dozens of research groups across the country have spent more than a decade perfecting the material to achieve standards that Awschalom's group has mastered in silicon carbide after only a few years of investigation.

Geraldine Rodriguez Gian Saldevia 기자
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