Diamond Defect Boosts Quantum Technology

ew research shows that a remarkable defect in
synthetic diamond produced by chemical vapor
deposition allows researchers to measure,
witness, and potentially manipulate electrons in a
manner that could lead to new "quantum
technology" for information processing. The study
is published in the January 31, 2014, issue of
Physical Review Letters.
Diamond Defect Boosts Quantum Technology
Washington, DC | Posted on February 4th, 2014
Normal computers process bits, the fundamental
ones and zeros, one at a time. But in quantum
computing, a "qubit" can be a one or a zero at
the same time. This duplicitous state can allow
multitasking at an astounding rate, which could
exponentially increase the computing capacity of
a tiny, tiny machine.
An "NV-" center can be created within a
diamond's scaffold-like structure by replacing a
missing carbon atom with a nitrogen atom (N)
that has trapped an electron making the center
negatively charged. Scientists can monitor the
center's behavior and thereby provide a window
for understanding how electrons respond to
different conditions. The center has the potential
to serve as a qubit in future quantum computers.
Electrons occupy different orbits around their
atom and, by analogy, spin like the Earth. For the
first time, Struzhkin and his team, led by Marcus
Doherty of the Australian National University,
observed what happens to electrons in these NV-
centers under high-pressure and normal
temperatures. Coauthor of the study, Viktor
Struzhkin at the Carnegie Institution for Science,
explained: "Our technique offers a powerful new
tool for analyzing and manipulating electrons to
advance our understanding of high-pressure
superconductivity, as well as magnetic and
electrical properties."
Struzhkin and team subjected single-crystal
diamonds to pressures up to 600,000 times
atmospheric pressure at sea level (60
gigapascals, GPa) in a diamond anvil cell and
observed how electron spin and motion were
affected. They optically excited the NV- centers
with light and scanned microwave frequencies in
a process called optically detected magnetic
resonance to determine any changes. The NV-
center is very sensitive to magnetic fields,
electrical fields, and stress.
Until now, researchers thought that the orbits of
the electrons that contribute to the defect's
electronic structure and spin dynamics were
localized to the area immediately surrounding the
vacancy. Doherty explained: "Our team found
instead that the electrons also orbit more distant
atoms and that the span of their orbits contract
with increasing pressure."
In addition to overturning previous beliefs about
the electron orbits, the researchers found a
sensitive means to measure pressure. This
method can detect changes in pressure of about
10 atmospheres in one second, even up to
pressures of 500,000 atmospheres (50 GPa).
"This work demonstrates that defects in diamond
have great potential as quantum sensors of high
pressure phenomena and, conversely, that high
pressure can be employed to study the quantum
phenomena of the defects," remarked Doherty.
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This work was supported by BES/DOE, DOE-
NNSA, the Australian Research Council Discovery
Project, Centre of Excellence for Quantum
Computation and Communications Technology,
and the Alexander von Humboldt Foundation.
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